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INTRODUCTION TO CAMOUFLAGE AND

DECEPTION

INTRODUCTION TO CAMOUFLAGE AND

DECEPTION

JV Ramana Rao Director (Retd)

Defence Laboratory Jodhpur

DEFENCE RESEARCH & DEVELOPMENT ORGANISATION MINISTRY OF DEFENCE NEW DELHI - 110 0 11

1999

DRDO Monographs/ Special Publications Series

INTRODUCTION TO CAMOUFLAGE AND DECEPTION

JV Ramana Rao

Series Editors Editor-in-Chief Associate Editor-in-Chief Associate Editor SS Murthy M Singh Ashok Kumar

Editor Asst Editor DS Bedi A Saravanan

Production Printing Cover Design SB Gupta SK Saxena SK Tyagi

Marketing RK Dua

O 1999, Defence Scientific Information & Documentation Centre (DESIDOC), Defence R&D Organisation, Delhi-110 054. All rights reserved. Except as permitted under the Indian Copyright Act 1957, no part of this publication may be reproduced, distributed or transmitted, stored in a database or a retrieval system, in any form or by any means, electronic, mechanical, photocopying, recording, or otherwise, without the prior written permission of the Publisher.

The views expressed in the book are those of the author only. The Editors or Publisher do not assume responsibility for the statements/ opinions expressed by the author.

ISBN: 81-86514-02-7

Printed and published by Director, DESIDOC, Metcalfe House, Delhi-1 10 054.

C O N T E N T S

Preface Acknowledgements

CHAPTER 1 INTRODUCTION

CHAPTER 2 MODERN MILITARY TECHNOLOGY AND ITS FUTURE TRENDS 2.1 Introduction 2.2 Land Warfare 2.2.1 Main Battle Tank 2.2.2 The Infantry 2.2.3 The Artillery 2 2.4 Role of Air Defence 2.2.5 Nuclear, Biological and Chemical Warfare

Surveillance and Target Acquisition Systems Command, Control and Communication (C3) Air Warfare Air Defence Aircraft Survival in the Enemy's Airspace Combat Aircraft and Weapons Future Air Warfare Naval Warfare Submarines Antisubmarine Warfare Future Trends

CHAPTER 3 CAMOUFLAGE IN NATURE 3.1 Introduction c3.2 Concealment 3.2.1 Colour Matching 3.2.1.1 Variable Colour Resemblance

Studies on Animal Colouration Countershading Disruptive Colouration Shadow Suppression Role of Concealing Colouration Concealment in Offence Studies on Concealing Colouration Advertisement The Warning Colouration Disguise Resemblance to Objects in the Background Diverting Attention to Non-vital Part Mimicry Other Forms of Camouflage Camouflage in Plants Evolution of Camouflage Conclusion

CHAPTER 4 VISUAL CAMOUFLAGE 4.1 Introduction 4 1 4.2 Visual Camouflage 41 4.3 The Human Eye 4 1 4.3.1 Visual Acuity 43 4.3.2 Dark and Light Adaptations 43 4.4 Characteristics of Light Relevant to Visual Camouflage 45 4.4.1 Colour 45 4.4.1.1 Geometrical Representations of Surface Colours 46

in Terms of Lightness, Hue and Saturation 4.4.1.2 Measurement of Colour 46 4.4.2 Texture 47 4.4.3 Brightness (Contrast) 47 4.5 Sensors in the Visible Region 48 4.5.1 Electrooptical Instruments 4.5.1.1 Image Intensifiers 4.5.1.2 Low Light Level Television

Lasers Rangefinding Target Designation Target Illumination Tracking Photography Platforms Photo-reconnaissance - Aerial Factors Affecting Photographic Reconnaissance Aerial Camera Advantages/disadvantages of Photographic Reconnaissance T V Cameras Optical Mechanical Scanners Linear Imaging Self-scanning Sensor (LISS) Military Satellites Factors Affecting Recognition in the Visible Region Shape Size Colour Texture Shadow Pattern Site Association Basic Principles of Camouflage in the Visible Region Hiding Arboriculture in Desert Region Screens Obscurants (Smoke Screens) Blending Colour Matching Countershading Disruptive Colouration Shadow Elimination Deception

Camouflaging of Military Objects by Disruptive Pattern Painting Studies on Disruptive Pattern Painting Dual Texture Gradient Pattern Paintings (DTG) Computerised Generation of Disruptive Patterns Camouflaging by Nets Properties of Net Materials Applications of Nets Manufacturers of Nets Psychological Camouflage Neurophysiological Principles of Visual Perception Studies on Target Characteristics and Target Context on Detection Psychological Studies Related to Camouflaging of nfilitary Objects Miscellaneous Camouflage Devices Foams Reflectance Camouflage Antishine Devices Vehicle Track Erasers Computer-based Evaluation of Camouflage New Areas of Visual Camouflage Metarners Spectral Camouflage

CHAPTER 5 INFRARED CAMOUFLAGE

Introduction What is Infrared Camouflage? Infrared Radiation Sources of Infrared Radiation Natural Sources Man-made Sources Carbon Arc Tungsten Lamp Xenon Arc Lamp Laser

Nernst Glower Globar Terminology Radiant Energy (U) Radiant Flux or Radiant Power (P) Radiant Emittance (W) Radiant Intensity (J) Radiance (N) Radiant Photon Emittance (Q) Irradiance (H) Spectral Radiant Flux (P, ) Radiant Emissivity (E) Radiant Reflectance (p) Radiant Absorptance (a) Radiant Transmittance (T) Laws Governing Radiation Emitted by Heated Objec Kirchhoff s Law Stefan-Boltzmann's Law Wien's Displacement Law RayleighJeansJ Law Planck's Law Properties of Infrared Radiation Propagation Characteristics Extinction Coefficient Atmospheric Windows Emissivity Measurement of Infrared Emissivity Ernissivity and Temperature Effects on Contrast Relative Effects of Temperature and Emissivity Differences on Radiant Flux Per Unit Area Infrared Sensors Pre- World War I1 Scenario Post- World War I1 Scenario Principle of an Infrared Sensing System Classification of Infrared Sensing Systems Infrared Detectors

Thermal Detectors Quantum Detectors Far Infrared Materials General Discussion on IR Detector Materials Performance Characteristics of a Detector Noise Equivalent Power (NEP) Detectivity (D) Infrared Sensing System Infrared Telescope Vidicon Photothermionic Image Converter Infrared Photography Evaporograph Thermal Imaging System Basic Elements of a Thermal Imaging System Objective Lens System Optomechanical Scanner Detector Bank Electronic Signal Processing and Display Performance Characteristics Applications of Thermal Imaging System Land Applications Air-borne Applications Sea Applications Manufacturers Differences Between Thermal Imaging System and Image Intensifier Future Trends General Considerations Concerning IR Operations with Thermal Imaging Systems Image Processing Single-element Scan Multi-element Scan Parallel-Scan Serial-parallel Scan Focal-plane Processing Arrays (FPAs)

Staring Arrays Schottky Barrier FPAs Charge Transfer Device Focal Planes IR Signatures of Military Objects and Backgrounds IR Signature of Aircraft IR Signature of Ship IR Signature of Tank IR Signature of Personnel IR Signature of Backgrounds Thermal Scenes - Characterisation of Backgrounds Scene Objects Computer Generated Imagery Components of Synthetic Scenes Paradigm for IR Synthetic Image Generation IR Signature Suppression (IRSS) of Warships Spectral Characteristics of IR Signature(s) of Ships IR Signature Suppression The Dres Ball The Eductor Diffuser IR Signature Suppression of Aircraft Suppression of Plume Signature Suppression of the Signature of Hot Parts Suppression of Signature of Aircraft Body Suppression of Signature of Unresolved Aircraft IR Signature Suppression of Tank Passive Countermeasures Reactive Countermeasures Signature Suppression of Ground Objects Suppression of Signature of Non-hardware Thermal Camouflage Equipment and Materials Disruptive Patterns Camouflage Screens Thermal Blankets or Tarps

CHAPTER 6 MICROWAVE CAMOUFLAGE

Introduction What are Microwaves? Properties of Microwaves Microwave Spectrum Radar Frequencies Historical Development of Microwaves Generation of Microwaves Microwave Vacuum Tube Devices Applications of Microwave Tubes Microwave Solid State Devices Microwave Sensors Principle of Radar Historical Development of Radar Radar Equation Typical Radar Types of Radars Continuous Wave (CW) Radar Frequency Modulated Continuous Wave (FM-CW) Radar Pulse Doppler Radar and Moving Target Indicater (MTI) Tracking Radar Side Looking Air-borne Radar (SLAR) Synthetic Aperture Radar (SAR) Millimeter Wave Radar Role of Radar in War Types of Radars Used in War Battlefield Surveillance Radar (BSR) Weapon Locating Radar (WLR) Air Defence Radar (ADR) Other Types of Radar Radar Cross Section (RCS) Expression for RCS Methods for the Prediction of RCS RCS of Flat Plate

RCS of Re-entrant Bodies (Corner Reflectors) 20 1 General Discussion on RCS of Simple Bodies 203 RCS of Military Objects 203 RCS of Aircraft 203 RCS of Ship 203 RCS of Tank 207 Advantages and Disadvantages of Prediction Techniques 207 RCS of Targets - Experimental Determination 208 Outdoor Ranges 209 Indoor Ranges 210 Methods for Reduction of RCS 210 Shaping 21 1 B-2 Bomber and F- 1 17A Fighter 212 Ship 2 12 Radar Absorbing Materials (RAMS) 2 13 Theory 2 14 Practical Radar Absorbing Materials 2 14 Types of Radar Absorbing Materials 215 Salisbury Screen 215 McMiIian Absorber 216 Dallenbach Layer 218 Jaumann Absorber and Graded Dielectric Absorber 218 Magnetic Absorber 2 19 Radar Absorbing Structures (RAS) 22 1 Circuit Analog Absorbers (CAs) 222 R-cards 223 Passive Cancellation 224 Active Cancellation 224 Current Research on Radar Absorbing Materials 224

CHAPTER 7 DECEPTION 7.1 Introduction 229 7.2 What is Deception ? 23 1 7.3 Disinformation 23 1 7.4 Psychological and General Aspects of Deception 232

7.5 Deception Equipment 7.5.1 Dummies 7.5.2 Decoys 7.6 Candidates for Dummies and Decoys 7.6.1 Criteria for Selection 7.6.2 General Criteria 7.6.3 Sensor-specific Criteria 7.7 Background for a n Effective Deception Strategy 7.8 Dummies/Decoys of Military Objects 7.8.1 Dummies and Decoys of Visible Region 7.8.2 Decoys (IR & Radar) 7.8.2. I Chaff Decoy 7.8.2.2 Infrared Flares 7.9 Various Decoys (Published in Literature) CHAPTER 8 MATERIALS FOR CAMOUFLAGE APPLICATIONS

Introduction Radar Absorbing Materials (RAMS) Magnetic Materials Dielectric Materials Artificial Dielectrics Conducting Polymers Chiral and Two-dimensional Polymers Schiff Base Salts Infrared Camouflage Materials Physical Principles Attenuat~on of Infrared Signatures Obscuration Surface Treatment Coating Materials for Camouflage in Infrared Region Coating Materials for Camouflage in Visible Region Paints Pigments for Forest and Jungle Areas Pigments for Desert Regions Pigments for Ocean Environment

8.4.2 Antireflective Coatings 8.4.3 Aqueous Foam 8.4.4 Smoke 8.4.5 Nets 8.5 Materials for Multispectral Camouflage 8.5.1 Surface Coatings 8.5.2 Composites 8.5.3 Multispectral Camouflage Nets 8.6 Materials for Acoustic Camouflage 8.7 Futuristic Camouflage Materials 8.7.1 Chromogenic Materials 8.7.2 Luminescent Materials 8.7.3 Polymers and Composites

CHAPTER 9 STEALTH TECHNOLOGY

Introduction What is Stealth? Historical Background of Stealth Technology Military Objects Requiring Stealth Stealth Aircraft LockheedJAirforce F- 1 17A Constructional Details of F-117A NorthropJBoeing B-2 Advanced Technology Bomber (ATB) Stealth Warships Acoustic Signature Radar Cross Section Infrared Signature Magnetic Signature Electric Signature Other Signatures Stealth Tank Stealth Submarine Stealth Helicopter Stealth RPVs

9.11 Stealth Missiles 312 9.12 Airship 312

CHAPTER PO R&D WORK ON CAMOUFLAGE AND DECEPTION IN DRDO 3 1 5 10.1 Introduction 10.2 Visual Camouflage 10.3 Infrared Camouflage 10.4 Microwave Camouflage 10.5 Multispectral Camouflage Materials 10.6 Naval Camouflage 10.7 Force Multipliers

CHAPTER 11 CONCLUSION Appendix - A Appendix - B Index

PREFACE

This introductory book on camouflage and deception is primarily intended for dissemination of knowledge and information in the field. The subject is a military science that has no counterpart in the civil sector, and as such, no university teaches and gives degrees in the field.

Camouflage and deception is an integral part of nature. For self-preservation, which is the central problem of biological evolution, all animals, small and big, both in offence and defence, adopt strategies and counterstrategies. These very principles significantly form the basis of camouflage in war. The means adopted by animals in nature have bewildering diversity and complexity all of which do not seem to have counterparts or could be duplicated even in the modern war of today. One typical example is that of the chameleon which almost instantaneously changes its colours in order to blend with its background. A s yet, there does not seem to be any means in the present day war by which a military vehicle can change its colour automatically in order to blend with the background, as it moves from one background to another.

The field of camouflage and deception was existing more as a military art than science, until and during World War 11. Since then, it has developed into a science. The field is inter-disciplinary and draws knowledge from several branches of science and engineering. The stealth technology, of the modern war of today, which greatly enhances the combat survivability of a fighter aircraft or bomber in the enemy's territory is a complex synthesis of several technologies. The rapid advancements that have been taking place in military sensor technologies, in turn, demand more and more sophisticated countermeasures. This is a war between the strategies and counterstrategies.

Countermeasures, signature suppression/signature management, stealth, low observables: these are the modern terms being employed in place of the classical terminology - camouflage, concealment and deception. The author, however, has entitled this book in the classical terminology.

This book has been written in eleven chapters based on the information available in open literature. Chapter 1, starting with the origin of camouflage, provides an introduction to the field. Chapter 2

provides glimpses of modem military technology and its future trends. This has been introduced in order to have a better appreciation of the importance of countermeasures in war. Chapter 3 deals with camouflage in nature. This provides the basic concepts of camouflage. Chapter 4 covers camouflage in the visible region. Camouflage in war started with ways and means to defy detection by the human eye. Before dealing with the different techniques of visual camouflage, the various sensors that are used in the visible region of the electromagnetic spectrum are briefly described. Chapter 5 starts with the basics of infrared radiation, then discusses the infrared sources- natural and man-made, infrared sensors and imaging systems, and infrared signatures of major military targets. Then the various infrared countermeasures are dealt with. Chapter 6 deals with basics of microwaves-generation, properties, microwave sensors, different types of radars, radar cross-section and its prediction and measurement, RCS of major military objects - aircraft, ships and tank, radar absorbing materials and paints, and RCS reduction methods. Chapter 7 briefly touches upon the role of deception in war in general and deception equipment in particular. Chapter 8 deals with camouflage materials for suppression of signatures in visible, infrared and microwave regions, including signatures of non-electromagnetic nature such as acoustic. Chapter 9 briefly touches upon stealth technology - its history, and its application to major military platforms. Chapter 10 gives a brief account of some aspects of research and development activities in the field carried out in DRDO laboratories. Chapter 11 summarises the various facets of the field and future trends.

The technologies associated with target acquisition are rapidly advancing. New tools, such as artificial intelligence, neural networks, pattern recognition and automatic target recognition, may further enhance sensor capabilities. These might lead to counterstealth technologies demanding counter-counterstealth measures.

The entire approach towards the field must be viewed from the scenario mentioned above. The field has to counter more challenges in future.

Hyderabad February 1999

J V RaMANA RAO

ACKNOWLEDGEMENTS

At the outset I would like to express my deep sense of gratitude to Dr APJ Abdul Kalam, SA to the Minister of Defence and Director General DRDO, Government of India, who has been the driving force behind this task and who has given me this assignment. I would also like to express my grateful thanks to Shri A Nagaratnarn, former Director, Defence Laboratory, Jodhpur (DW), for going through the manuscript of the book and providing several valuable suggestions.

I have been greatly helped by Defence Research and Development Laboratory (DRDL), Research Centre Imarat (RCI), Defence Metallurgical Research Laboratory (DMRL), Hyderabad; Aeronautical Development Establishment (ADE), Electronics and Radar Development Establishment (LRDE), Aeronautical Development Agency (ADA), and Centre for Artificial Intelligence and Robotics (CAIR), Bangalore; Research and Development Establishment (Engineers) (R&DE Engineers)), Armaments Research and Development Establishment (ARDE), Institute of Armament Technology (IAT), High Energy Materials Research Laboratory (HEMRL), and College of Military Engineering (CME), Pune; Defence Materials and Stores Research and Development Establishment (DMSRDE), Kanpur; Instrument Research and Development Establishment (IRDE), Defence Electronics Applications Laboratory (DEAL), Dehradun; Defence Science Centre (DSC), Solidstate Physics Laboratory (SPL), and Defence Scientific Information and Documentation Centre (DESIDOC), s el hi; and Combat Vehicles Research and Development Establishment (CVRDE), Chennai, in extending library facilities, through Xerox copies of articles and papers published in open literature. I express my sincere thanks to the Directors of all these laboratories.

I take this opportunity to thank Prof J Srihari Rao, Regional Engineering College, Warangal, for his support in the preparation of material pertaining to generation of microwaves and radars; Prof Raghavendra Gadagkar, Indian Institute of Science (IISc), Bangalore; Prof J Sobhanadri and Prof VRK Murthy, Indian Institute of Technoloo (IIT), Chennai for their valuable suggestions and discussions.

I gratefully acknowledge the support provided by Dr AR Reddy, former Director, DW for extending every type of facility that I have asked for and to Dr SS Murthy, Director, DESIDOC and Dr Ramesh Kumar, Director of Materials, and their colleagues for their support and valuable suggestions.

It is a great pleasure to acknowledge the excellent support provided by Dr N h m a r , and Dr SR Vadera, DM, in writing the chapter on Materials for Camouflage Applications. But for their support, it would have been difficult for me to do justice to this chapter. I would also like to express my sincere thanks to Shri Anil Das, DW, for his assistance in writing the chapter on Deception.

I take this opportunity to thank Shri P Rama Seshu, Dr Krishna Kumar, Shri SN Puspak, Shri Ramesh Chandra Saxena, Shri BL Soni and Shri N Bohra, my ex-colleagues in DW, for the services rendered by them.

I gratefully acknowledge the support provided by Dr Kartikeya V Sarabhai, Director, Centre for Environment Education (CEE), Ahmedabad. I would also like to place on record my sincere thanks and appreciation to Smt Meena Raghunathan, Programme Coordinator; Shri Mukesh Barad, Artist; and Shri DM Thumber, Artist of CEE for their excellent work in the preparation of some of the illustrations of the Chapter - Camouflage in Nature.

I would like to place on record my sincere thanks and appreciation to Shri MS Verma, Shri RP Sharma, Shri Virendra Vikram and Shri Mangi La1 for preparing drawings of figures; to Shri Madho Singh and Rajender Vimal for preparing colour transparencies; and to Shri ML Choudhary, Shri BT Mathai, Shri M R Pate1 and Shri Ajay Singh, of DW, f ~ r the excellent assistance provided by them in word processing.

J V Ramana Rao

CHAPTER 1

INTRODUCTION

The word 'camouflage7 has its origin in the French word camoufler which means 'to disguise7'. When the word entered the English dictionary initially, it had a limited meaning, implying concealment or disguise of military objects in order to prevent detection by the enemy. The only sensor available in the early days was the human eye. The means to camouflage a military object were foliage and other locally available material.

The concept of camouflage is as old as nature, and it has been an integral part of it. All animals, small and big, are found to employ several methods of concealment and disguise for self-preservation, both in defence and offence. Practically no animal is safe, since for every animal there is a predator. Both the predator and the prey have to adopt strategies for their survival. Thus there is a n evolutionary arms race between different species and also within the same species. In the progress of biological evolution, both the predators and the prey have to constantly and equally improve their strategies and then pass them from generation to generation2s3. In the arms race in nature there exists a bewildering diversity in the strategies and counterstrategies adopted by different animals. All these techniques may be termed as camouflage and deception in nature2r3. Although there may not be a counterpart in the present day arms race to each and every strategy adopted by animals in nature, these very principles, by and large, form the basis of camouflage in war. Whether it is concealment or disguise, deception is inherent in all the methods.

Human civilization, beginning with primitive man, has been using camouflage, concealment and deception in various forms for different purposes, particularly in wars. The basic philosophy remaining one and the same, the changes that have come are in the methodology of application and the levels of sophistication.

Several examples can be cited from ancient wars in which camouflage was extensively utilised with great advantage. The

2 Introduction to Camouflage and Deception

German legend4 "The Nibelungenlied" describes the camouflaging cap, the 'Tarnkappe'. Siegfried wins the cap from the dwarf king Alberich. The cap makes him invisible. It makes him defeat Brunhilde, the Queen of Iceland, in battle. The could not conquer Troy for ten years, not until they employed a ruse-the wooden Trojan horse. The Greeks hid themselves in its belly. The horse was pulled inside the city by the Trojans which led to the conquer of Troy. The use of twigs and leaves on the caps and moving under natural cover by Genghis Khan's mounted mongols, and leaving of camp fires burning by George Washington after departing from the camp, are but a few examples where last minute decisions on camouflage measures had changed failures to successes.

Camouflage was employed by the French army during World War I in order to prevent detection of guns and vehicles from the enemy's observation5. Camouflage which was existing more as a military art became a science during World War 11. At that time a wide range of military objects, such as individual soldiers, guns, vehicles, tanks, airfields and shipyards, needed protection against aerial observation through naked eye and aerial photographs6. This provided the impetus to develop the field of camouflage and deception on scientific lines. Even during World War 11, the field was essentially confined to the ways and means to disguise military objects against human observation, i.e. camouflaging of military objects against sensors which were available in the visible region. Technological advances in the field of remote sensing covering a wide range of the electromagnetic spectrum have in turn demanded equivalent countermeasures.

Prior to World War 11, camouflaging of military objects against sensors employed in the infrared region of the electromagnetic spectrum did not seem to have been employed, as no such sensors were available. In the subsequent wars, such as in the Vietnam War, new detectors beyond the visible region of the electromagnetic spectrum came into use. The need for camouflaging military objects beyond the red end of the visible region had arisen with the development of infrared false colour photographic film during World War I1 which provided an impetus for research and development in the field of infrared radiation. Since then, the field has seen rapid growth, in particular in the area of military reconnaissance, surveillance and target acquisition. This in turn has put great stress on countermeasures to defy detection by infrared systems. Thus progress in the field of infrared engineering became synonymous with the development of military infrared7. Much of the work done in the field was classified and not available in open literature. The field of infrared camouflage known under different names - infrared

Introduction 3

countermeasures, infrared signature suppression, etc - has become vital to the success of any military operations in the various theatres of war - the land, the air and the sea.

Radar had played a very important role in World War I1 when several developments took place in radar technology in US, Britain and Germany. This in t u rn had pu t a great s t ress on radar countermeasures - a modern name for microwave camouflage. The major military objects which need microwave camouflage are the fighter aircraft, the naval warship and the tank. These objects can be detected by the i r d i s t inc t microwave s igna tures . The countermeasures involve suppression of these signatures. The microwave signature of a military object is known today as its radar cross-section (RCS). Thus the problem of microwave camouflage is one of reducing RCS of military objects of interest to such a n extent that the object escapes detection by radar. All military objects do not require microwave camouflage. Only those objects which come under the influence of radar threat are the candidates for microwave camouflage.

The development of radar is synonymous with the development of microwave electronics . There have been t r emendous advancements in radar technology in the post-World War I1 period. Developments such a s digital signal processing and phased array antennas have greatly enhanced radar capabilities. All these developments will continue to demand radar countermeasures.

Throughout history, besides the conventional methods of camouflage, deception has been employed simultaneously as a force multiplier and to enhance combat survivability. Application of deception techniques in all their subtlety and sophistication peaked during the 1991 Gulf War. The technically developed and heavily resource-backed Allied Forces brandished advanced decoys and deception equipment. The Iraqis effectively displayed deception by relatively simpler techniques8-lo. In many situations, camouflage combined with deception would be more effective. In some cases, it is deception equipment alone that can meet the requirement. Camouflage is concerned with the suppression of signature(s) which the military object may have by which it may be detected. Deception is concerned with simulation of the concerned signature(s). Increase in the signal-to-noise ratio increases detectability of the object by the sensor concerned. Increase in the noise-to-signal ratio increases the degree of camouflage. The objective of various camouflage methods is to increase noise-to-signal ratio.

The technological explosion of the 20th century - in the fields of electronics, computer revolution, materials research, and sensor


technology have brought in unimaginable advances in military hardware, weapons, weapon controls, and delivery systems, mobility, reconnaissance, surveillance and target acquisition systems. Simultaneously, along with these developments, the role of countermeasures has become increasingly important, demanding improvements in the existing countermeasures and development of new methods and techniques.

The conventional methods of camouflage and deception are no longer adequate in the present-day advanced technology warfare scenario. The field has acquired new dimensions under the names such as stealth technology, low observable technology, very low observable technology, or signature management. In this context, the conventional methods of camouflage, concealment and deception serve only the preliminary stages. The concept of multispectral/ polyspectral camouflage under the name stealth technology has to embody countermeasures to detection by radar, infrared, visible and acoustic sensors and any other sensor that may be employed. Stealth or low observable technology as applied to a weapon platform such as a combat aircraft considers several aspects of the design right from inception with the primary objective of incorporating low observable features without affecting the performance of the aircraft".

REFERENCES 1. Hinkle, C. W. The Encyclopedia Americana. The International

Reference Work. Americana Corporation, Washington DC, 1958. p 268-70.

2. Owen, D. Camouflage and mimicry. Oxford University Press, 1980.

3. Cott, H. B. Adaptive coloration in animals. Methuen & Co. Ltd. London, 1966.

4. Jurgen Erbe. Thoughts on camouflage and deception. Milita y Technology. 1987, XI(9), 85-87.

5. Now you see me, now you don't - military camouflage. Defence, 1993, XXIV(2), 10-14.

6. Goetz, P. W. (Editor-in-Chief). The New Encyclopedia Britannica. Encyclopedia Britannica Inc., 1988. p 77 1.

7. Hudson, R.D. Infrared system engineering. John Wiley & Sons, New York, 1969.

8. Soviet Electronic National Defence. 1985, 35-42. 9. Soviet military thought. Milita y Review. 1982, 6, 25.

Introduction 5

10. International Defence Review. 1985, 8, 1235-57. 11. Schmieder, D.E. & Walker, G.W. Camouflage, suppression

and screening systems. In Countermeasure Systems, Vol7, Edited by David H. Pollock. The Infrared & Electrooptical Systems Handbook, ERIM, Michigan & SPIE Optical Engineering Press, Washington, 1993.

CHAPTER 2

MODERN MILITARY TECHNOLOGY AND ITS FUTURE TRENDS

2.1 INTRODUCTION Modern military technology and its future trends have been

discussed at length by Friedman et a1 in their book on Advanced Technology Warfare1. The information given in this chaptkr is based on the above reference.

It is not difficult to comprehend for a layman to what levels science and technology have progressed and the impact they have made in the various theatres of war - the land, the air and the sea. The impact of the technological explosion of the 20th century has made space another combat zone through the employment of satellites. Developments in the field of electronics, the computer revolution, and improvements in the performance of existing materials and development of new materials satisfying critical requirements, have significantly added to the armamentarium of military hardware making the weapon platforms, weapon systems and controls more and more sophisticated and complex. This can be very well gauged, for example, from the ballistic and cruise missiles currently available.

If the military hardware continues to grow in sophistication at the present rate, it would be difficult to predict the nature and magnitude of future wars. As weapon platforms and weapon systems grow in their capabilities to zero-on to the target, the availability of effective countermeasures will become a key factor for combat survivability.

2.2 LAND WARFARE Today's war on the ground has become highly complex with

the introduction of improved technologies into combat systems which has greatly enhanced the range and lethality of the weapon


systems employed by ground forces. To counteract the multitude of highly potent sensors and weapon systems with which the airspace above the ground is filled, there are equally potent air defence systems on the ground providing protection to the battlefield on the ground.

2.2.1 Main Battle Tank The main battle tank (MBT) has a major role in land warfare.

Its design has been continuously absorbing the developments in related technologies with special reference to fire power, protection and mobility. As a result, the speed (reaching a maximum of around 70 kmph on level ground), the calibre of the main guns, the firing range, the accuracy of fire, the thickness of the armour, have all increased. Different countries have their own designs with variations in relative importance to fire power, mobility and protection. Besides the large calibre gun, tanks have night vision equipment, thermal imagers, electronic fire control computers and navigational aids which enhance the tank's performance as a weapon system.

The most vulnerable part of the tank is its armour (particularly against top attack) which is receiving maximum attention for protection against anti-tank weapons - missiles, rockets and guns. The American M- 1, German Leopard-2, and the Soviet T-80 utilise composite armours for effective protection. The British CHOBAM amour has layers of metals, ceramics and plastics, which can defeat the High Explosives Squash Head (HESH) round. This armour has been countered by the long rod penetrator projectile which can pierce through the armour. Then came the reactive armour. This utilises an explosive on its outer surface, to prevent the projectile from entering the armour. The fourth generation Russian tanks, such as T-64, T-72 and T-80 have incorporated some special features. Their gun can fire Armour Piercing, Fin- Stabilized Discarding Sabot (APFSDS) projectile, which can defeat the High Explosive Anti-Tank (HEAT) ammunition as well as High Explosive Squash Head (HESH). India is also manufacturing the Fin- Stabilised Armour Piercing Discarding Sabot (FSAPDS) projectile. In India, DRDO has developed Kanchan a m o u r which is being incorporated in MBT Arjun.

Significant advances can be expected to take place in the tanks of the future, mainly in terms of fire power, manoeuvrability and armour strength, to provide greater strength to land warfare and to withstand the anti-tank weapons - mines, missiles, rockets and guns, particularly the anti-tank guided missiles (ATGMs) whose technology has been greatly advancing in terms of their guidance systems, fire power and ability to distinguish between real and false targets.

Modern Military Technology and its Future Trends 9

Besides MBT, robotic tanks such as robotic obstacle breaching tank (ROBAT) -which can breach minefields in hostile environment, autonomous land vehicles, and programmable robot observer with logical enemy response (PROWLER) will be new additions from US. This class of vehicles will be equipped with microcomputers with artificial intelligence software and a variety of sensors that will enable them to patrol the battlefield. Various other vehicles such as Armoured Personnel Carriers (APCs) - battle taxis, BMPs (Boyeva Mashina Pekhoti) of Russia, and BFVs (Bradley Fighting Vehicle) of US are being deployed for a number of roles. 2.2.2 The Infantry

Modern technology has brought in many changes in the battlefield environment of the infantryman. These changes have resulted in increased mobility, improved anti-tank capability, better personal equipment, more portable weapons, etc.

The infantryman of the future will probably wear a helmet made of kevlar, then a number of sensors such as image intensifier, thermal imager, and gyro-stabilised laser target designator, as well as a pocket-sized computer with several tens of megabytes of memory.

2.2.3 The Artillery Major technological advances have enhanced the performance

of artillery. Revolutionary advances in the field of electronics have brought in improved communications, observation means, survey capabilities and artillery fire. The artillery has a variety of munitions, including nuclear weapons, at its disposal.

New @idance systems, such as those used in US Copperhead and Precision Guided Munitions (PGMs), have greatly enhanced their capabilities while hitting the targets. The Multiple Launched Rocket System (MLRS), which was under development by US, UK, Federal Republic of Germany and France, had a provision to incorporate a terminal guidance warhead to defeat armour and another warhead for chemical weapons. A development for rocket artillery weapons will be the Cannon Launched Guided Missile (CLGP). Another US concept is the Seek and Destroy Armour (SADARM) which has the capability to seek and destroy individual targets. Yet another development would be STAFF (Smart Target Activated Fire and Forget). This will be fired in the general direction of the target. Radio waves reflected from the target would be picked up by an antenna in the nose of the projectile which is guided by an onboard computer.


2.2.4 Role of Air Defence The role of air defence is to protect ground installations and

forces from aerial attacks. This is accomplished by radar directed Surfac-to-Air Missiles (SAMs). The US designed PATRIOT counters high speed aircraft and missiles a t all altitudes as well as jammers and other electronic countermeasures (ECMs) . 2.2.5 Nuclear, Biological and Chemical Warfare

The prospect of nuclear war (although not fortunately resorted to till now) significantly changes military planning. Here it is the dispersal of troops that is to be adopted instead of the normal method of concentrating them.

Chemical warfare (CW) has high potential. It involves the use of nerve agents, toxins and psychological agents. These nerve agents are derived from Tabun, Sarin and Soman. In biological warfare (BW), toxins derived from bacteriological organisms such as botulin would be employed. Psychological agents a re derived from psychochemicals such as (lysergic acid diethylamide) LSD. These chemical agents can be spread by several means such as aerial bombs, artillery shells or by aerosol sprays. 2.2.6 Surveillance and Target Acquisition Systems

For rapidly reacting to any adverse situation in the battlefield, it is essential to find out the concentration and disposition of the opponent. Several advances have taken place in this area which have greatly enhanced battlefield surveillance. The means through which this is accomplished are from ground, air, as well as space. The equipment used include optical instruments, electrooptical devices, radars, and thermal imaging systems. These can be hand held, tripod mounted, mounted on ground platforms, helicopters, remotely piloted vehicles, drones, aircraft and satellites. 2.2.7 Command, Control and Communication (C3)

The electronic revolution has made a great impact on command, control and communication (C3) systems in the battlefield and elsewhere. Information can flow from FEBA (Forward Edge of the Battle Area) and FLOT (Forward Line of Own Troops). The operational area will have a matrix of trunk nodes. The principal component of a node is a vehicle containing a computer-controlled electronic switching device which functions as an automatic exchange. The exchange connects one user to another.

The jobs of the widely dispersed and highly sophisticated arms of today have become simpler and rapid, with the advances that have taken place in C3.

Modern Military Technology and its Future Trends 1 1

2.3 AIR WARFARE Today war in .air is backed by more advanced technologies

than war in the other two theatres - land and sea. Obviously it is more complex and sophisticated, and greatly influences the war in other theatres. Technologies have advanced to such an extent that today there may be no need for a pilot, or human crews in a combat aircraft, from which targets such as a tank or ship or another craft can be hit and destroyed. What used to be done by the pilot's eyes is now performed by a wide range of sensors, viz., electrooptical, infrared, microwave etc. Further, cruise missiles carrying warheads and satellites have added new dimensions to war in general and to air warfare and space warfare in particular.

2.3.1 Air Defence It is known that for an aircraft to survive in enemy's air space,

it has to fly at the lowest possible levels to minimise radar detection. This has brought attention on to low level air defence systems. The introduction of Airborne Warning and Control System (AWACS) which utilises a multimode radar at a height of less than 10,000 m (10 km) has extended the range of vision to about 400 km, enabling detection of targets flying close to the ground. Besides, AWACS can provide a lot of information on friendly and hostile forces. But, at the same time, every defence system is countered by measures incorporated in the combat aircraft. These include: Electrooptical Countermeasures (EOCM), Infrared Countermeasures (IRCM), and Eelectronic Countermeasures (ECM). The various types of missiles that home on to targets can be countered by jammers, decoys and other false sources. The Triple A (anti-aircraft) or SAMs can engage any aircraft or missile at a range of 3-8 km.

2.3.2 Aircraft Survival in the Enemy's Airspace Aircraft survival in the enemy's airspace depends upon its

ability to escape detection by all possible sensors which the enemy might use. The aircraft has to be made stealthy, involving reduction in Radar Cross-Section (RCS), suppression of infrared emissions and all visible signs such as contrails. Stealth technology takes care of these aspects to reduce the chances of detection. Also, to distract detection by infrared sensors, expendable decoys in the form of flares and infrared pulse emitters are employed.

Protection of airfields during major wars is not an easy task. The accepted line of action is to proyide additional support airfield defences employing hardened aircraft shelters and aircraft that can take off between the craters.


2.3.3 Combat Aircraft a n d Weapons The combat aircraft carries on board a variety of sensors for

different roles - ranging from navigation to weapon delivery, including recovery a t the base. These sensors could be active or passive, and are described elsewhere. In order to reduce emissions which can be detected, use of active sensors has to be reduced. The weapons carried by the aircraft are guided missiles which receive guidance from external radar, or lasers, or have self-guidance which rely upon IR radiation emitted by the target. The antiship missile flies extremely low in the sea-skimming mode to escape detection. Most of the antiship missiles use active radar homing. Today there is a wide range of air-to-surface missiles such as wire-guided antitank missiles having a range of a few hundred meters and cruise missiles which can home on a target over 3,000 km. For air-to-air operations, the weapons are guns and guided missiles. Air-to-Air Missiles (AAMs) of short range depend on IR homing. Fire and forget come under this category. The other category of AAMs is of medium range which relies on radar homing.

2.3.4 Future Air Warfare The present-day stealth technology which is using passive

measures may be countered by further developments in sensor technologies. So, for enhancing the chances of survival in the airspace, active measures of stealth will probably be necessary. They involve manipulation of the electromagnetic and nonelectromagnetic signatures associated with the aircraft to create confusion. Another problem which has still not been probably solved is the suppression of IR signature of the aircraft which is being utilised by missiles for homing on.

2.4 NAVAL WARFARE Naval warfare has incorporated the latest technologies in its

surface warships, surface weapons, submarines, submarine weapons, sensors, and command, control and communications.

During the last five decades, there have been rapid strides in surface warship technologies. The surface warship ha s to simultaneously perform several tasks, viz., Air Defence (AD), Anti- Submarine War (ASW), besides antisurface roles. In order to perform these roles, it has to equip itself with active and passive sensors such a s Air Defence Radars, Surface Surveillance Radars, Electrooptical Systems, Hull-Mounted Sonars, and Variable Depth Sonars. In terms of warship armament, a surface warship has to equip itself with weaponry to attack and defeat other surface warships, submarines and aircraft. The most important weapon

Modem Military Technology and its Future Trends 13

for both offensive and defensive actions is the missile. The French Exocet is an antiship missile (ASM) which can be ship-launched as well as air-launched. The Soviet antiship missile 'Shaddock' has a nuclear warhead. The US Navy's Harpoon has penetration blast warhead. In general, antiship missile guidance is programmed in such a manner that the missile hits at the central portion of the hull so that the vital services of the ship are damaged.

There are however countermeasures to antiship missile, such as chaff decoys which provide a screen around the ship, and infrared flares which provide alternate targets to the incoming surface and air-launched missiles. Besides missiles, other armaments include modern naval guns, such as the US Navy's Phalanx CIWS (Close- in Weapons System). The characteristic feature of this system is that it has extremely fast reaction time and heavy volume of fire.

With regard to aircraft carrier scene, the wkstern navies have dominated for many years. The vertical/short takeoff and landing V/STOL aircraft are comparatively inexpensive. The primary role of sea-based aircraft are Antisubmarine Warfare (ASW), strike/ attack, Air Defence (AD), electronic warfare and Airborne Early Warnilng (AEW) . 2.4.1 Submarines

The submarine is an effective underwater weapon platform. Submarines have both acoustic and non-acoustic signatures. In order to reduce the chances of detection, their signatures have to be suppressed. Research efforts are being directed towards comparatively less noisy submarines with better speeds and deeper diving capabilities. Nuclear propulsion is one of the greatest achievements in the submarine technology of the post World War I1 period. Now the submarine does not have to come to surface for refilling its air requirement and recharging its batteries, and its speed far exceeds that of attacking surface vessels.

The torpedo has been the underwater weapon for attack and patrol submarines since long. In comparativeIy recent years, new weapons are being added. Submarine-Launched Cruise Missile (SLCM) is one such weapon which can have a range up to 1,000 km. One important role being played by the submarine is mine laying. The important sensors of a submerged submarine are sonar and hydrophone.

2.4.2 Antisubmarine Warfare Submarine detection technology is critical to antisubmarine

warfare. The characteristics of a moving submarine provide the necessary means of detecting it. Navies of the world are

f:4 Introduction to Camouflage and Deception

concentrating their R&D efforts towards improving the existing methods, and discovering new methods of detection, localisation and categorisation of submarines.

Antisubmarine warfare mainly involves five steps: search, contact, approach, attack, and close combat and disengagement. During the search stage, a surface warship or a submarine or airborne aircraft searches for the submarine in a certain region. In this stage, passive sensors together with inputs from other platforms are employed. Contact stage involves detection and classification. Detection implies the presence of an object in a given area. Classification tells whether the object detected is a submarine. From the nature of the signature received from the submarine, further information on the type and class of submarine is obtained. The approach stage utilises passive means for localisation of the target. In the attack stage the weapon, usually a torpedo, is launched. In the final stage the submarine comes back to its original position of quiet. Mines also play a major role in antisubmarine warfare.

Besides sonar (the active sensor) and hydrophone (the passive sensor) other non-acoustic means, such as the wake, which sets in temperature disturbances, can be used for detection of submarines. Submarines are also detectable by the electrical and magnetic fields they create.

2.5 FUTURETRENDS Probably the most important contributory factor to the

advanced technology warfare of today is the electronic revolution - developments in solid-state electronics, miniaturisation of electronics, very high speed integrated circuits (VHSIC) and digital computers. All these developments are finding application in military hardware and military systems and will continue to do so to enhance the combat effectiveness in the various theatres of war. A wide range of the electromagnetic spectrum will find increasing applications in modern warfare. Millitimeter wave systems may soon find the~r way into weapon systems. Radiometers as passive seekers can also be used in dual mode along with active systems such as lasers. Millimeter wave seekers will find application in antitank missiles.

Developments may take place in sonar, which is the means for locating and tracking submarines. Passive sensors provide only the bearing of the target. Active sonar signals alert the victim. Towed- array sonars which have been developed in comparatively recent years can meet the requirement of long range detection of targets.

As regards electrooptical systems, non-imaging infrared homing systems are used in antiaircraft missiles and antiship missiles.

Modem Military Technology and its Future Trends 15

Imaging infrared systems are used in air-to-ground weapon systems and night vision systems.

Lasers have found several applications in war, such as missile guidance, ranging and target designation, and laser-guided bombs. The Rockwell AGM-114A Hellfire was one such missile guidance application. Laser has entered the field of radar. The British Aerospace Dynamics Laserfire is an example. This type of radar has the advantage of high angular resolution as well as good range resolution. The Hyper-Velocity Missile which was being developed by Vought for USAF is a multifunctional system. It can not only detect but classify multiple moving tagets and transmit the commands to a formation of several missiles.

In the area of communications, a combination of advancements in the field of electronics, such as integrated circuit electronics and microprocessers and computer technology has brought in flexibility and reliability in military command and control.

Electronic warfare {EW) consists of countermeasures to enemy's surveillance, target acquisition, tracking and guidance systems. Radar and infrared warning receivers detect signals from hostile radars and tactical missiles respectively. The chaff and flare decoys are the countermeasures against radar and infrared homing systems.

The shape, scope and speed of future wars may be estimated mainly from the technological,advancements taking place in the field of electronics, materials and computers. With this background of the present-day military technology, it would not be difficult to assess the role and importance of camoufl age and deception in war. All vital equipment need the cover of camouflage and/or deception for sustenance, combat survivability and for successfully completing missions.

REFERENCE 1. Friedman, R.S.; Miller, D.; Gunston, B.; Richardson, D.;

Hobbs, D. & Warmer, M. Advanced technology warfare. Salmander Books Ltd., London, 1985.

CHAPTER 3

CAMOUFLAGE IN NATURE

3.1 INTRODUCTION The origin of the biological world may be traced back to a few

thousand million years. It consists of a multitude of organic species. The central problem of biological evolution is self-preservation. The basic requirements of self-preservation are food, habitat, security, procreation, rearing the offspring, and transferring the genetic characteristics to the next generation. The various organisms have to constantly interact with the environment in which they live, with other species, and with their own species. The interactions are not simple. The environment taken as a whole is a complex web consisting of the organism's surroundings, habitat, predators, enemies and competitors. Adaptability to this complex web is the primary requisite for survival. The probability of sunrival is determined by the degree of adaptability.

The foremost requirement for an animal to survive is food. A simple food chain consists of plant-plant feeder-predator1. While some animals depend on plants for their food, a majority of animals are predatory. Although in this food chain, only one predator is given, four or even five predators may be added to the chain. It may be said that the predator at the end of the chain is free from other predators. Practically no animal is safe, and for every animal there is a predator. For survival, both the predators and the prey have to adopt strategies. The prey is constantly on the alert to avoid recognition by the predator. The predator is constantly on the lookout to locate and capture its prey for food. This is an arms race consisting of strategies and counterstrategies, the former for defence and the latter for offence. Evolutionary arms race takes place between different species as well as species of the same kind. It is a conflict between the predator and prey, between hunter and hunted, and the aggressor and the victim of aggression.


In the process of biological evolution, both the predator and the prey have to constantly and equally improve their strategies and then pass them from generation togeneration. The strategies adopted by the animals in nature are highly varied and there do not seem to exist counterparts for all of them even in the present-day arms race. In the arms race in nature, there exists a bewildering diversity of strategies and counterstrategies. All these techniques may be termed as camouflage.

As applied to nature, camouflage may be defined as the means by which animals escape the notice of predators or as a device or expedient designed to conceal or deceive. Whatever be the strategy adopted, deception is inherent in all of them since the true appearance of the animal is replaced by a false one.

3.2 CONCEALMENT Concealment is a widely adopted method of camouflage. In

nature, there are a variety of backgrounds characterised by homogeneity and heterogeneity in colour, and structural simplicity and complexity. The predominant colours of various backgrounds are green and brown, besides sea blue and grey. These colours occur either singly or in combination, along with tonal and hue variations. Forests, woodlands, mountainous and rocky regions are complex backgrounds while deserts, seas and snow regions are simple.

Cott gives an excellent account of camouflage in nature in his book2, 'Adaptive Coloration in Animals'. The various principles that are found to operate by which different animals are concealed in their respective backgrounds are:

Colour matching Countershading Disruptive colouration and Shadow suppression

3.2.1 Colour Matching The first and the foremost requirement for an animal to blend

with its background is to have on its body the prevailing colour of the environment.

Several varieties of caterpillars, butterflies, grasshoppers, mantids, frogs, and birds are predominantly green in colour, which reduces their probability of detection in their green background. Lizards and several other species living on boughs, tree trunks and barks are usually brown in colour. Animals living in deserts have on their bodies dusty brown coats. In snow-bound areas white colour is predominantly seen on birds and mammals. Fishes which dwell in water have transparent bodies. Those living on sea shore and sea

bottom bearr OPE their bodies appropriate colours h m a ~ s i n g with their backgrounds. Multicolours are found on species which Eve on flowers.

Thus concealment is attained in animals in nature, broadly, by bearing colour resemblance to their respective environment.

3.2.1.1 BJariarhle Cobour Resemblance Many anirnals, besides possessing colour resemblance, have

the ability to change their colour depending upon the requirement. During their life history, while in the young stages, many geometridae like the oalc beauty in the larval form display colour charactc~ristics of twigs on which they rest2. As the lava grows and becomes arr adult, it changes its colour to that of the bark on which it Jlves. Some i~lsects such as buttedies exhibit variation in colour between wet and dry seasons. Some ~ t h e r animals have the ability lo rapidly iz?d almost instantaneously change their colour in their effort to attain the colour of the background. Chameleon and cuttlefish are two examples of this kind. There are some other categories wh5.h exhibit polyrnorg~hism in colouration3. In some of these cases it has been proved that by being different from the rest of the crowd animals escape attention of their predators or prey. This is probably because atlixnals develop a search image by which they ignore unfamiliar or different animals.

Some animals, besides possessing colour resemblance, have structural resemblances to their respective backgrounds. The yellow-wattled Lapwing2 builds its nest on bare ground and lays its eggs in a small depression in the ground (Fig. 3.1). In spite of the heterogeneity of the background in terms of coliaur and structure, the bird, its nest and its eggs blend remarkably weli with surroundings. Similarly, the sandgrousa: which lays pinkish eggs on hare ground among fallen leaves, the wood cock among fallen and broken oak trees, the ringed plover morrg pebbles a d the ptarmigan among Iichen-covered rocks, all are beautiki examples of camouflage in complex backgrounds. Specid mention may be made of the Eurasion bittern Botunurus stelaris [Fig, 3.2) which nests =among reeds'. When in danger, it straigl~fcns its head and erects its neck in a straight line. A s the reeds of the backgro~lntd are blown with the winds, the bird too, ,dong with the vertical stripes on its body and neck, sv~ays, blending well with the background. Other examples of colour and structurd resemblance YO their immediate background, namely, leaves,

Camouflage in nature 21

sticks, pebbles etc, are leaf insects, stick insects, walking sticks, and leaf-like frogs.

3.2.1.2 Studies on Animal Colouration Pioneering work on animal colouration was carried out by

Poulton4j5. According to him, the green colour of various caterpillars is due to the presence of chlorophyll which is derived from the food they eat. The green colour of tree frogs is due to selective absorption and reflection of light6. Light falling on the animal through green leaves is predominantly yellow in colour, which is absorbed by the deep-seated melanophores. The guanophores reflect back radiation lying in the green region. Where there is no green foliage, blue radiation is more pronounced. Laboratory experiments showed that exposure to blue light results in brown pigment, which explains the brown colour of animals living in brown backgrounds. By and large, the green and brown pigments of grasshoppers are either genetical or produced in response to stimuli from the environment. Rapid changes of colours in cuttlefish are due to the presence of special cells in the skin which contain black melanin. Regulation of melanin can cause different kinds of colours7. The physiological mechanisms responsible for such rapid changes in colour are complex. Several factors come into play such as reflex activities induced through the sense of sight, controlled by hormones in the blood, or in some cases due to direct action of light on skin.

It is unlikely that adaptive colouration is accidental. There is positive evidence in support of the biological value of visual concealment as a means of protection from predators which hunt by sight. The studies of Poulton and Sanders8, di Cesnolag, Younglo, S~ rnne r~~ . ' * J~ , Carrick14, Iselyls, Collenette16 and Cheesman17 are in support of this view.

3.2.2 Countershading The principle of countershading is also found to be operative

in the camouflage scheme of animals2. An animal possessing colour matching with its background can still be recognised by the unequal illumination of different parts of the body. Figure 3.3 shows a white cock against white background; yet, it is conspicuously seen and recognized. The back of the bird receives more light from the top, its breast receives less light, and its vertical parts have the same illumination as that of the background. This gives rise to unequal illumination on different parts of the body. The light and shade effects so produced completely offset the colour matching of the bird with the background and renders the animal recognisable. Thus, despite


Figure 3.3. A white cock against a white background. colour matching with background, any solid object can be recognised by the effect of light and shade alone. Even if the cock were coloured by a darker shade and seen against the darker background, it can still be recognised. But the bird can be rendered invisible by making its back darker and belly lighter. This destroys the light and shade effects. The solid body of the bird appears to get flattened. Then the colour matching becomes effective, rendering the bird invisible. This is known as the principle of countershading. This effect is observed in various fishes and many desert animals-mammals, birds, snakes, lizards, etc. Another example is the hare which bears a darker tone on its back and lighter tone on its belly.

The theory of concealment by countershading was put forth by Thayer18-21. Figure 3.4 illustrates Thayer's principle of countershading. Figure 3.4(a) shows the appearance of light and shade produced in a uniformly coloured body matching with the background and illuminated from above, and figure 3.4(b) the appearance of a counter-shaded body illuminated uniformly from all directions. Figure 3.4(c) gives the appearance of flatness caused by corrntershading and light falling from the top.


Figure 3.4. Thayer's principle of countershading. (a) Self-coloured when illuminated from above (b) Countershaded when uniformly illuminated (c) Top-lighting and countershaded

Figure 3.5. Bush Buck - An illustration of obliterative shading.


Another example of this principle can be seen in Bush Buck (Fig. 3.5). In this case the animal has white spots on its flanks. These spots resemble flecks of sunlight falling on its body through vegetation. The animal at first glance melts into the background2.

Effects of countershading can also be produced by employing patterns of alternating black and white stripes or spots or patches. When these patterns are observed from different distances, depending upon the density of the patterns, a point will be reached where, because of failure of resolution, they blend and provide the necessary countershading effects. MottramZ2 was the first to discuss the effects of such patterns. A glaring example of this kind from nature is the zebra (Equus burchelligranti, Fig. 3.6). The zebra has black and white bands on its body. The black stripes are dense where it receives more illumination, and less dense where it receives less illumination. This type of pattern produces the necessary countershading effects. Also, the stripes which are perpendicular to the contour, obliterate (discussed subsequently) the form of the animal. The zebra escapes attention from its predators during dawn and dusk when it is vulnerable to attack. There are many other animals which have patterns producing countershading effects a t blending distances at which they are vulnerable to attack.

Figure 3.6. Zebra - Black and white stripes producing countershading.


Although countershading in nature gives a degree of invisibility to the animal, further studies are needed to establish its role and value.

3.2.3 Disruptive Colouration Colour matching combined with countershading provides

adequate concealment against a simple background of uniform colour when the animal is not in motion. But this is an ideal situation. Most of the animals move from place to place and hence are seen by their predators against constantly changing backgrounds. Under these conditions nature provides effective camouflage to the various animals by the application of disruptive colouration2.

The two important characteristics by which any object is recognised are'specific surface area and specific contour by which it is bounded. These two characteristics fix the size and shape of the object by which it is recognised. So, if these two characteristics are

Figuse 3.7. Disruptive patterns on some snakes.

26 Intmduction to Camouflage and Deception

destroyed, recognition is not possible. This is what is accomplished in disruptive colouration. A large variety of animals in nature are camouflaged by disruptive colouration, where animals wear on their bodies patches of irregular shape oriented at random in two or three colours and of different sizes. Figure 3.7 shows some of the disruptive patterns found on some snakes. These patterns divert the attention of the observer away from the real appearance of the animal, and atterltion is drawn towards these patches which bear no relationship to its actual shape and size. The efficacy of the patterns depends upon a number of factors. Firstly, some of the patches should have the same colour as that of the background, while that of the others should strongly differ from that of the background. Secondly, the patches should cut the contour of the body perpendicularly rather than running parallel to the contour. Thirdly, there should be maximum colour contrast between adjacent patches. A single object wearing these patterns is replaced by a large number of dissimilar and small objects. In this way the real appearance of the animal is

(a) (b) (c) (dl Figure 3.8. Disruptive patterns illustrating the principle of

differential blending.


masked. The pattern by itself may be dazzliig but it contradicts the form of the animal.

Another feature observed in these patterns is that the patches bear striking resemblances to the various objects of the background in which the animal moves. Figure 3.8 shows how the recognition is rendered more and more difficult. Left hand figures of each series are the real forms of a fish, a butterfly and a bird, seen against a uniform white background. Figures number (b) of each series show these three animals with disruptive patterns, but not matching with their background. Despite mismatch with the background colour, there will be some difficulty experienced in recognising their true form. In figures (c) and fd) of each series, the background matches with one element of the pattern. One of the elements blending with the background, if not totally preventing recognition, at least ddays the recognition of the true form of the animal. This illustrates differential blending. Figure 3.9 illustrates the principle of maximum disruptive contrast between the background and one of the elements

Figure 3.9. Principle of maximum disruptive contrast.


of the background. First figures of each horizontal row are shaded in such a way as to correspond with their respective backgrounds,

Figure 3.10. Rana adspersa.

black in the first, white in the second, and intermediate in the third. The second figure of each horizontal row has a pattern. The white elements in the middle first row sharply differ in contrast from the black background. The black element in the middle second row sharply differ in contrast from the white background. The white element in the middle third row differs in contrast from the grey background. When one looks at these figures from a distance, the elements of the figure having maximum contrast from the background distract attention from the true form of the figure. In the third of each row, the backgrounds are nonuniform, having broken surroundings. In such a situation, the efficacy of the patterns is further enhanced. This principle has wide application is nature.

Even the simplest disruptive pattern such as the one found on the body of the East African Rana adspersa (Fig . 3.10) is effective in hindering recognition. The body of the frog bears brown and green colours. A yellow stripe which is conspicuous, starting lfrom the snout and running along its back, divides the body approximately into two parts. The yellow line resembles a blade of grass or twig; further it bisects the frog into two apparently different entities. The conspicuous yellow line catching the observer's eye diverts the attention away ffom the real form of the animal. Such simple patterns are found in nature on many kinds of birds, grasshoppers etc.


Flipre 3.11.1Megalixalusfomasinii. Besides patterns which produce disruption of form and size, there are patterns which join together separate parts of the body, rendering recognition difficult. When component parts like legs, wings, eyes, mouths and fins are separately seen, recognition is easier. But if by some means these parts are brought together, giving the impression of a single entity, recognition becomes difficult. The tiny frog


Megalixalus fonasinii has stripes on its back and on legs. While the animal is in resting position it folds the limbs close to the sides of the body. The appearance totally contradicts the real form of the animal (Fig. 3. 1 1).

Similar techniques are adopted by giraffes, jaguars, grasshoppers, moths, frogs, mantids, etc., to escape recognition by predators or grey. Figure 3.12 shows a woodcock. Here disruption is produced by dazzle.

The most difficult of all the organs which are difficult to conceal are the eyes. Whatever be the background, a circular or round object attracts maximum attention, and a s such its concealment is necessary for hindering recognition of the animal. During the day, in the case of tree frogs and snakes, the round eyes get constricted into narrow slits. In the case of the common frog, there is a dark patch of irregular shape around the eye extending into the body which masks the eye.

3.2.4 Shadow Suppression An animal which is otherwise well camouflaged by the methods

mentioned above can still be recognised indirectly by its shadow cast on the ground under the action of sunlight. The probability of recognition by the shadow depends on the nature of the surface on which it is cast. If the surface is smooth, the shadow is well defined; if the surface is uneven or irregular, the shadow is distorted or broken, making recognition difficult. Shadow suppression becomes more important in the case of animals such as lizards, birds, butterflies, moths, etc. whose habitats are relatively flat and even, and exposed to sunlight.

Butterflies compress their shadow into unrecognisable form by resting with their wings folded and orient their body with respect to the direction of sunlight in such a way that the shadow gets reduced practically into a line. Some butterflies tilt their bodies or wings in such a way that their shadow is hidden. Moths keep their body and wings depressed to the surface and crouch low. In some categories of animals, the dark elements in their disruptive patterns and the shadow together make recognition difficult.

3.2.5 Role of Concealing Colouration There is no general agreement among biologists as regards the

role of cryptic dress worn by various animals on their bodies in nature. The question that arises is whether the cryptic colours are merely accidental or whether they have been evolved for survival or concealment. This aspect has been discussed at length by Cott2.


In general, there is a striking resemblance between the colouration put on by frogs, toads, grasshoppers, butterflies, etc. and their surroundings. Such a phenomenon is also observed in several birds such as bustards, larks, night jars etc. In all these cases, the cryptic dress is providing protection from the predators, enemies etc. On the other hand, there are some birds such as eagles, falcons, kites, harriers, etc. which do not possess any concealing colouration and are conspicuous, the reason being that they have no natural predators. Birds such as macaws, cockattos, and ostriches have strong and sharp beaks, as a means of protection. There are others which live in a colony in large numbers. There are some other categories of birds which depend upon their speed of motion, evade attack by diving or bolting and are aerial in habits. In other words, cryptic colouration becomes necessary in the case of animals of terrestrial origin of small, moderate size and unarmed.

Camouflage is effective only when the animal is stationary. However perfect the cryptic dress may be, while in motion its efficacy abruptly drops down. In the case of birds which are nocturnal in habits and rest during the day, camouflage becomes a vital biological necessity. The bird kiwi spends its daytime in holes and burrows, and so it does not need any camouflage, and it does not put on any cryptic dress. Likewise, starlings, kingfishers, woodpeckers which rest in holes, in trees and underground, have no cryptic dress. In the case of birds like larks and bustards which lay their nests on bare grounds, cryptic colouration is well developed. During periods of incubation there appears to be a correlation between appearance and nesting habits. In the case of eggs which are not otherwise protected, such as those of larks, pipits, sandpipers, and sandgrouses, they are all cryptically coloured in such a way as to blend with their surroundings. On the other hand, the eggs of woodpeckers, hornbills, barbets and parrots are white and hence do not possess any cryptic colouration; but they do not need protection by camouflage as the nests are inside holes in trees and underground. But there are a few exceptions where the eggs which are otherwise not protected do not have any cryptic colouration. In general, there seems to be a close correlation between the cryptic dress of eggs and the environment in which they are incubated. It appears that, in general, cryptic colouration and cryptic instincts have evolved in response to the need for concealment.

3.2.6 Concealment in Offence Camouflage is employed not only in defence but also in offence.

Animals can sense events happening at a distance through sight,


sound and smell. While capturing prey, animals alter their appearance, suppress noise and obliterate smell. For aggressive as well as protective function, the predatory animals employ the same principles of camouflage. The tiger and the panther are practically invisible to their prey almost till the latter are attacked and caught.

Whatever be the degree of camouflage, once the animal is in motion, it attracts attention. Basically, the problem of concealment in offence differs from that in defence. The prey anim,al, while in defence, remains motionless and escapes observation by its cryptic dress. On the other hand, the predator cannot remain still, it has to be active and in motion, and still not attract the attention of its prey. Besides adopting cryptic colouration, the movements of the predator have to be stealthy and skilful while approaching and attacking the prey. Fishes are good examples of stealthy approach. Firstly, their bodies are excessively thin, and secondly their movements are precise and cautious. All these render the fish most inconspicuous to its prey. Until the final assault, the leaf fish is least observable by its prey. During the assault, the approach is so slow and stealthy that its movements do not produce any detectable noise. Other examples of stealthy approach are those of the spider and snake while catching their prey.

Owls, while in flight and approaching their prey, depend upon a combination of darkness and silence. The flight of an owl, in spite of high speed, is not accompanied by detectable noise. This is due to structural modifications of its feathersz3. For masking scent, animals make use of the wind direction. They approach the prey against the wind.

3.2.7 Studies on Concealing Colouration Cott2 gives an excellent review of the views of different workers

on the function of concealing colouration. Deanz4 is of the view that cryptic colouration in animals is accidental, in support of which he cites some instances. According to Cott, those instances cannot be used as an argument against the theories of cryptic colouration. The combined use of colour matching, obliterative shading and disruptive colouration, all in a single animal, cannot be chance effects without any biological significance. We find a general agreement between the cryptic dress in a wide variety of animals and the diverse surroundings in which the respective animals live. All the observed facts taken together indicate that concealing colouration has been an important end rather than an incidental by-product.


Some critics put forth the argument that cryptic colouration is the result of a physical process as opposed to the need for concealment in nature. But the function of concealing colouration in biological evolution is not to be mixed up with the mechanism of the concealing colouration. Although the physical and chemical mechanisms vary in different cases, the underlying optical principles of concealment are the same in all the cases. Cryptic colouration does not imply total immunity from attack but chances of survival are increased. Some critics argue that it is stillness which is more important than concealing colouration. Whether the animal is at rest or in motion, a cryptic colour scheme has its significance. Some argue that since many animals do not have colour vision, concealing colouration cannot be adaptive. Many studies have been carried out on birds, insects, fishes and mammals, and it is established that several animals have a wide range of colour vision. Another argument against adaptive colouration is that many protected forms are widely preyed upon in nature. Adaptive colouration cannot afford protection against all animals.

The greatest supporters of the theories of concealing colouration, warning colouration and mimicry have been without exception naturalists - Darwin, Wallace, Bates, Alcock, Belt, Hale Carpenter, Graham Kerr, Hingston, Hudson, Julian Huxley, Miles Moss, Mortesen, Poulton, and Shelford -whose experience of natural history has convinced them of the adaptive significance of the various phenomena of cryptic colouration2.

Literature on this subject has been descriptive. Relatively few experiments have been carried out to test the validity of the theory of concealing colouration. It is of utmost importance that further data based upon experimental observations should be obtained in relation to the theories of concealing colouration.

3.3 ADVERTISEMENT A s anti-thesis to concealment in nature, there are several

animals which by their appearance are conspicuous. Although this characteristic is the opposite of concealment, it serves the same vital needs - food, safety and reproduction. By being conspicuous the animal advertises its inedible qualities. Thereby it is avoided by the predator. The colours red, black and yellow in combination are utilised for drawing attention.

3.3.1 The Warning Colouration In contrast to concealment which involves cryptic colouration,

stillness and concealing attitude, advertisement involves display of


conspicuous colours, movements, sound, smell etc. Animals which take recourse to advertisement have structures and behaviours which can cause real harm when attacked. The poisonous stings and bites of many insects, spiders and snakes are examples of the above category. These animals combine warning colouration along with occasional use of the sting or bite to keep the danger away. There is hardly any need for a stinging animal like bee, wasp or hornet to hide its appearance and not let the victim know what struck it. So, instead of hiding, it leaves a permanent impression of its appearance and sting in the mind of its victim, so that bee or wasp is never approached subsequently.

Salamanders (Salamandra rnaculosa), tree snakes (Dipsado morphus dendrophilus), sea snakes (Pelamydrus platurus), and sawflies (Athalia cordata) use the combination of black and yellow colours for drawing attention. Some collect in large numbers with the same aim.

The porcupine, when threatened, employs several means to give warning to its enemy. The anirna.1 opens its thorny spines, it stamps, squeals, rattles and stinks when in danger. The puffer fish (Tetrodontidae) grows in size and resembles a balloon when in danger. The little porcupine fishes gather together creating an appearance of a large fish when in danger. There are some animals which exhibit bright colours all of a sudden when there is a threat. Snakes employ hissing sounds for drawing attention. Some animals release irritating secretions. There are categories of animals which emit nauseous odour. Butterflies employ odour for conspicuousness. There are some other categories of animals which possess tough bodies. All these animals, with the dangerous characteristics they possess, remain conspicuous so that they are avoided.

There are some animals which are palatable and defenceless. But they get protection by borrowing the characteristics of aposematic animals which are inedible. Also some birds build their nests very near the habitat of poisonous insects such as bees, wasps, etc.

3.4 DISGUISE Disguise is employed both in defence and in offence.

3.4.1 Resemblance to Object's i n the Background Many animals resemble objects of their background. Some

fishes resemble dead leaves, some ,other categories acquire the appearance of thin leaves either by compressing or by depressing their bodies or by a combination of obliterative shading and disruptive patterns. Butterflies have wings resembling thin leaves.


Some insects resemble curled leaves. Some type of moths, beetles etc., resemble bark. Lizards, frogs, and birds also utilize this type of deceptive appearance. Some insects such as mantids, grasshoppers, caterpillars and tree frogs resemble lichen. Some insects bear striking resemblance to bird droppings. Some moths resemble broken twigs. Marine organisms resemble shingle, sea grass etc2.

3.4.2 Diverting Attention to Non-vital Part Some animals divert the attack of their predators to non-vital

parts of their bodies. A round object attracts maximum attention. The wings of mantids, moths, butterflies etc possess eye-like round patterns at the extreme ends of their wings. Even if the predator attacks, the prey escapes with a minor injury to the extreme end of its wing. In some lizards, the tail end is brilliantly coloured to attract attention. When attacked, the lizard escapes with a minor injury to the tail end.

Some animals create the impression of a head at a wrong part of its body. Head is a vital organ both for the predator and prey. A predator, while capturing the prey by ambush, conceals its head. Some predators possess characteristics by which they allure the prey to the most dangerous part of the body. Some animals like mantids resemble buds of flowers. When insects visit these buds they become food to these animals2.

3.4.3 Mimicry We have seen that some animals have an inbuilt mechanism by

which they can sting or bite and also have warning colouration in order to warn their victims against future attempts at harming them. There are some animals which by merely mimicking the warning colouration of the above animals escape attacks from their predators and enemies. Mimicry has been extensively studied in the case of butterflies3. The most common type of mimicry is called Batesiari mimicry in which a harmless or a nonpoisonous species mimics a harmful or a poisonous one. This form of mimicry was first demonstrated by Bates over a hundred years ago. The North American monarch butterfly is inedible and also warningly coloured. The viceroy butterfly which is palatable mimics the monarch butterfly. Thus by mimicking the monarch in warning colouration, the viceroy gets protection from predators. There is another type of mimicry known as Mullerian mimicry, after the name of the naturalist Fritz Muller. In this form of mimicry two species of butterflies that are both unpalatable mimic each other. Animals try to mimic only those parts which can actually be seen or observed. Mimicry is employed by several species of insects, birds and snakes. Some moths mimic wasps, some spiders look like ants, and some flies bear resemblance to bees.


3.5 OTHER FORMS OF CAMOUFLAGE Besides visual camouflage which we have discussed so far,

there are other forms such as ultraviolet camouflage, auditory camouflage and olfactory camouflage3. Many insects have vision in the ultraviolet region. So the colours and patterns on flowers and insects as perceived by them are quite different from our perception.

A s regards auditory camouflage, we may cite the example of small birds which, in their effort to help their fellow birds, produce sound signals at the approach of a predator. These alarm calls are produced in such a way that the predator cannot locate the source of the signals. MarlerZ5 has discussed the physical basis of auditory camouflage. His conclusions have been found to be generally correct2'j. Other examples of auditory camouflage are some species of mynas and bulbuls which imitate the calls of other birdsz7.

Of the three senses -- sight, sound, and smell - it is the smell that plays the important role in the case of most insects. In all species of ants, most individuals in the colony are sterile and labour for the colony, helping the queen to produce more offspring. In some species of ants, adequate numbers of workers are not produced. As such, these species capture workers from other species which produce a large number of workers. The captured workers, when they become adults, work for the colony. StudiesZ8 showed that the Fomica Sunguinea group sprays large quantities of decyl, dodecyl and tetradecyl acetates on the colony raided. This disturbs the olfactory sense of workers in the colony. In the process, sufficient number of pupae are captured to meet the requirements of slaves whose number in the other colony is less.

3.6 CAMOUFLAGE IN PLANTS Camouflage is also found to occur in plants. But it cannot be

as effective as in the case of animals, the reason being that the former are immobile, and the latter have the mobility which helps them to fool their predators continuously. The tips of leaves and tendrils of passion flowers mimic eggs of butterflies. Thereby they prevent the Heliconius butterfly from laying eggs on them. Some types of orchids mimic female bees and wasps. Male bees and wasps rest on these flowers for copulation and in the process pollination takes place3.

3.7 EVOLUTION OF CAMOUFLAGE The phenomenon of industrial melanism is an example to

illustrate the evolution of camouflage in nature. According to the


theory of natural selection only a small fraction of the individuals of any species produced in each generation wil

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