Sneak preview of A Guide to Australian Monitors in Captivity

reptilepublications

By Dr Danny Brown BVSc (Hons) BSc (Hons)

A Guide to…AustralianMONITORSin Captivity

A Guide to…

Australian M

ON

ITORS in Captivity By D

r Danny Brow

n BVSc (H

ons) BSc (Hons)

reptilepublications SNEAK PREVIEW

ABOUT THE AUTHOR ....................................................................................................................................13

ACKNOWLEDGEMENTS .................................................................................................................................................14

INTRODUCTION ...............................................................................................................................................................16 GENERAL MANAGEMENT .............................................................................................................17

PET SUITABILITY ...........................................................................................................................................................................................17CHOOSING YOUR STOCK ..............................................................................................................................................................17Selecting an Individual Monitor ............................................................................................................................................18

HANDLING AND HYGIENE ............................................................................................................................................................19 TRANSPORTATION ....................................................................................................................................................................................22 Short Journeys.....................................................................................................................................................................................................22Long Journeys ......................................................................................................................................................................................................23Timber Boxes ..........................................................................................................................................................................................................24Plastic Containers ...........................................................................................................................................................................................25

PURCHASE AND FREIGHT ETIQUETTE ..................................................................................................................25 Buyers ................................................................................................................................................................................................................................25Sellers .................................................................................................................................................................................................................................26

LEGAL REQUIREMENTS ....................................................................................................................................................................27

GENERAL SAFETY ........................................................................................................................................................................................28

SECURITY ....................................................................................................................................................................................................................29

QUARANTINE ......................................................................................................................................................................................................30

HOUSINGINDOOR ENCLOSURES ..................................................................................................................................................31Rack Systems ..........................................................................................................................................................................................................31Tubs .......................................................................................................................................................................................................................................31Tanks ....................................................................................................................................................................................................................................32Pits ...........................................................................................................................................................................................................................................32Timber Enclosures .........................................................................................................................................................................................33Glass, Perspex or Plastic Moulded Commercial Terrariums ......................................................33 Mesh Terrariums ...............................................................................................................................................................................................34

OUTDOOR ENCLOSURES ........................................................................................................................................34Pits ...........................................................................................................................................................................................................................................35Aviaries ............................................................................................................................................................................................................................36

ENCLOSURE SIZE ..........................................................................................................................................................................................38Minimum Enclosure Sizes .................................................................................................................................................................38

COMPATIBILITY ...............................................................................................................................................................................................38

CONTENTS

VENTILATION ......................................................................................................................................................................................................40

SUBSTRATE .............................................................................................................................................................................................................40

Sand ......................................................................................................................................................................................................................................40

Soil ...........................................................................................................................................................................................................................................41

Gravel ..................................................................................................................................................................................................................................41

Scoria ...................................................................................................................................................................................................................................42

Leaf Litter .....................................................................................................................................................................................................................42Potting Mix ................................................................................................................................................................................................................42Sphagnum Moss ...............................................................................................................................................................................................42Peat.........................................................................................................................................................................................................................................42Bark and Wood Chip...................................................................................................................................................................................43Wood Shavings ...................................................................................................................................................................................................43Corn Cob Litter ....................................................................................................................................................................................................43Walnut Shell Litter .........................................................................................................................................................................................43Alfalfa/Lucerne Pellets ...........................................................................................................................................................................43Compressed Timber Pellets ...........................................................................................................................................................43Compressed Newspaper Pellets .............................................................................................................................................44Zeolite and Clumping Cat Litter .............................................................................................................................................44Paper ....................................................................................................................................................................................................................................44Artificial Grass ......................................................................................................................................................................................................44Indoor/Outdoor Carpet ........................................................................................................................................................................44

HIDE SITES .......................................................................................................................................................................................................44 Vertical Hide Sites ..........................................................................................................................................................................................45Horizontal Hide Sites ................................................................................................................................................................................46

ENCLOSURE ENRICHMENT ...................................................................................................................................48Surface Litter ..........................................................................................................................................................................................................48Branches and Hollows.............................................................................................................................................................................48Artificial Plants ....................................................................................................................................................................................................48Dried Plants ..............................................................................................................................................................................................................49Live Plants ...................................................................................................................................................................................................................50

HEATING ...............................................................................................................................................................................................................51

HEAT CORD OR TAPE ..............................................................................................................................................................................51

HEAT MATS ..............................................................................................................................................................................................................51

HEAT ROCKS ..........................................................................................................................................................................................................52

CERAMIC HEATERS....................................................................................................................................................................................52

GLOBES...........................................................................................................................................................................................................................52Standard Incandescent Globes ................................................................................................................................................52Reflector Globes ...............................................................................................................................................................................................53Reptile Lamps .......................................................................................................................................................................................................53Halogen Bulbs ......................................................................................................................................................................................................53Infrared Globes ...................................................................................................................................................................................................53Mercury Vapour Lamps (MVLs) ..............................................................................................................................................54Metal Halide Bulbs ........................................................................................................................................................................................54

LIGHTING ............................................................................................................................................................................................................56 THE SCIENCE OF LIGHTING .......................................................................................................................................................56Visible Light ..............................................................................................................................................................................................................56Infrared ............................................................................................................................................................................................................................56Ultraviolet A (UV-A) .....................................................................................................................................................................................56Ultraviolet B (UV-B) ......................................................................................................................................................................................56Ultraviolet C (UV-C) ......................................................................................................................................................................................59

LIGHTING OPTIONS .................................................................................................................................................................................59UV-B Emitting Fluorescent Tubes .........................................................................................................................................60Black Lights ...............................................................................................................................................................................................................60Compact UV-B Emitting Lamps ...............................................................................................................................................61Mercury Vapour Lamps .........................................................................................................................................................................61‘Modified’ Halogen (Quartz or Dichroic Halogens) Bulbs ............................................................63Metal Halide Lamps ....................................................................................................................................................................................63

THERMOSTATS ...................................................................................................................................................................................63Probe Thermostats .......................................................................................................................................................................................64On/Off Thermostats ....................................................................................................................................................................................64Dimming Thermostats ............................................................................................................................................................................65Pulse Proportional Thermostats ............................................................................................................................................65

HUMIDITY .......................................................................................................................................................................................................65

FEEDING METHODS AND NUTRITIONINVERTEBRATE FOOD ITEMS ......................................................................................................................67Crickets—Acheta domestica .................................................................................................................................................................67Cockroaches ............................................................................................................................................................................................................68Mealworms—Tenebrio molitor .........................................................................................................................................................68King Mealworms or Superworms—Zophobas morio .................................................................................69Maggots/Flies/Pupae—Musca vetutissima ..................................................................................................................69Slaters .................................................................................................................................................................................................................................70Silkworms—Bombyx mori and other caterpillars ............................................................................................70Termites ..........................................................................................................................................................................................................................70Earthworms—Lumbricus terrestrius ...........................................................................................................................................70Locusts—Chortoicetes terminifera .................................................................................................................................................70Spiders ..............................................................................................................................................................................................................................71Fruit Flies—Drosophila species .....................................................................................................................................................71Snails—Helix aspersa and other species .........................................................................................................................71Crustacea—Freshwater Crayfish, Prawns and Shrimp ......................................................................71Waxworms—Galleria mellonella ....................................................................................................................................................72Wild Fodder ..............................................................................................................................................................................................................73Nutritional Data Averages for Invertebrate Diets .....................................................................................73

VERTEBRATE FOOD ITEMS ................................................................................................................................75Rats and Mice ........................................................................................................................................................................................................75Chicks and Small Birds ...........................................................................................................................................................................76

Guinea Pigs ...............................................................................................................................................................................................................76Fish ..........................................................................................................................................................................................................................................76Reptiles ............................................................................................................................................................................................................................76Nutritional Data Averages for Vertebrate Diets ...........................................................................................77

ARTIFICIAL DIETS .......................................................................................................................................................................78

CARNIVOROUS/INSECTIVOROUS DIETS ...........................................................................................................78San Diego Zoo Diet ......................................................................................................................................................................................78

CULTURING INSECT FOOD ITEMS ..................................................................................................79Crickets—Acheta domestica .................................................................................................................................................................79Speckled Feeder Roaches—Nauphoeta cinerea ..................................................................................................82Locusts—Chortoicetes terminifera .................................................................................................................................................82Slaters .................................................................................................................................................................................................................................83

DIETARY SUPPLEMENTS .........................................................................................................................................84

CALCIUM ......................................................................................................................................................................................................................84Gut Loading .............................................................................................................................................................................................................84Dusting.............................................................................................................................................................................................................................85

PROTEIN........................................................................................................................................................................................................................86

FEEDING FACILITIES ...........................................................................................................................................................86 FEEDING PROBLEMS .........................................................................................................................................................88

TREATMENT ..........................................................................................................................................................................................................89Assist Feeding .....................................................................................................................................................................................................89Force Feeding ........................................................................................................................................................................................................89Tube Feeding .........................................................................................................................................................................................................90

BREEDINGVISUAL SEXING ..................................................................................................................................................................................91Colour .................................................................................................................................................................................................................................91Size ..........................................................................................................................................................................................................................................92Femoral and Preanal Pores .............................................................................................................................................................92Hemipenal Bulges ..........................................................................................................................................................................................93Paracloacal Spur Structures ..........................................................................................................................................................93

OTHER SEXING TECHNIQUES .................................................................................................................................................94Hemipenal Probing .....................................................................................................................................................................................94Hemipenal Popping....................................................................................................................................................................................94Hemipenal Transillumination .....................................................................................................................................................95Hemipenal Observation ......................................................................................................................................................................98Hemipenal Plug Observation .....................................................................................................................................................99Hemipenal Palpation ................................................................................................................................................................................99Ultrasound .................................................................................................................................................................................................................99Radiography—X-ray Examination ..................................................................................................................................100

BREEDING AGE.................................................................................................................................................................................102

COURTSHIP ...............................................................................................................................................................................................102

MATING ...............................................................................................................................................................................................................102

STRATEGIES TO ENHANCE BREEDING SUCCESS ......................................102COOLING ................................................................................................................................................................................................................102SEPARATION .....................................................................................................................................................................................................104

REPRODUCTION ...........................................................................................................................................................................104REPRODUCTIVE STRATEGIES .............................................................................................................................................104EGG TYPE ................................................................................................................................................................................................................105CLUTCH SIZE .....................................................................................................................................................................................................105BREEDING FREQUENCY ...............................................................................................................................................................105REPTILIAN REPRODUCTIVE SENILITY .............................................................................................................105GRAVIDITY ...........................................................................................................................................................................................................106CARING FOR BREEDING FEMALE MONITORS ......................................................................................107

NEST FACILITIES ...........................................................................................................................................................................108 ARBOREAL SPECIES .............................................................................................................................................................................109TERRESTRIAL SPECIES ....................................................................................................................................................................109

EGG LAYING .............................................................................................................................................................................................111 EGG MANAGEMENT ............................................................................................................................................................................111 Collecting and Handling .................................................................................................................................................................111Determining Egg Viability ............................................................................................................................................................113

ARTIFICIAL INCUBATION .......................................................................................................................................116INCUBATION FACILITIES .............................................................................................................................................................116CONTAINERS .....................................................................................................................................................................................................116 HEATING ...................................................................................................................................................................................................................117TEMPERATURE CONTROL .........................................................................................................................................................119INCUBATION MEDIUM ....................................................................................................................................................................119Vermiculite .............................................................................................................................................................................................................119 Perlite ..............................................................................................................................................................................................................................119Sphagnum Moss ...........................................................................................................................................................................................120 True Peat Moss ................................................................................................................................................................................................120Coir Peat Moss ................................................................................................................................................................................................120No Substrate .......................................................................................................................................................................................................120

INCUBATION REGIMES ...................................................................................................................................................................121 TEMPERATURE DEPENDENT SEX DETERMINATION .................................................................121

NATURAL INCUBATION ..............................................................................................................................................122

HATCHLING CARE .....................................................................................................................................................................122

FEEDING ...................................................................................................................................................................................................................122 Feeding Frequency ..................................................................................................................................................................................123Supplementation ........................................................................................................................................................................................123

LIGHTING ................................................................................................................................................................................................................123 HOUSING .................................................................................................................................................................................................................123 HEATING ...................................................................................................................................................................................................................123COMPATIBILITY ...........................................................................................................................................................................................123

COMMON DISEASES AND DISORDERSDISCLAIMER ............................................................................................................................................................................................124NUTRITIONAL DISORDERS ...............................................................................................................................125 OBESITY ....................................................................................................................................................................................................................125METABOLIC BONE DISEASE (CALCIUM/VITAMIN D3 DEFICIENCY) ..............125Early Onset Metabolic Bone Disease ..........................................................................................................................125Late Onset Metabolic Bone Disease ............................................................................................................................126Delayed Metabolic Bone Disease .....................................................................................................................................126Reproductive Metabolic Bone Disease ...................................................................................................................127

GUT IMPACTION ........................................................................................................................................................................................127

PARASITIC DISORDERS ..............................................................................................................................................129INTERNAL PARASITES .....................................................................................................................................................................129EXTERNAL PARASITES ....................................................................................................................................................................130

SKIN DISORDERS ........................................................................................................................................................................131DYSECDYSIS.......................................................................................................................................................................................................131SCALE ROT ............................................................................................................................................................................................................131 NAIL, TOE AND LIMB DISORDERS...................................................................................................132

EYE DISORDERS .............................................................................................................................................................................132EYE TRAUMA.....................................................................................................................................................................................................132

PHOTO-KERATOCONJUNCTIVITIS ............................................................................................................................133PRIMARY BACTERIAL EYE INFECTIONS ..........................................................................................................133

RESPIRATORY DISORDERS ................................................................................................................................133BACTERIAL PNEUMONIA ...........................................................................................................................................................134

VITAMIN A DEFICIENCY ...............................................................................................................................................................134

HUMIDITY RELATED PROBLEMS ..................................................................................................................................134 PARASITIC PNEUMONIA ............................................................................................................................................................134

TRAUMA ............................................................................................................................................................................................................135 BITE INJURIES .................................................................................................................................................................................................135 THERMAL BURNS .....................................................................................................................................................................................135

REPRODUCTIVE DISORDERS .......................................................................................................................136 PRE-OVULATORY AND POST-OVULATORY STASIS (EGG BINDING OR DYSTOCIA) ..........................................................................................................................................136

UTERINE INFECTION ..........................................................................................................................................................................138 HEMIPENAL INJURIES AND INFECTION ..........................................................................................................139 CONGENITAL DEFECTS ..................................................................................................................................................................140

NASAL AND ORAL DISORDERS .............................................................................................................142

NASAL ABRASIONS—NOSE RUBS ............................................................................................................................142 JAW DISEASE/PERIODONTITIS/STOMATITIS.........................................................................................142

ADMINISTRATION OF MEDICATIONS ...................................................................................143

SUBCUTANEOUS OR INTRAMUSCULAR INJECTIONS ............................................................143

LIQUID ORAL MEDICATION ...................................................................................................................................................144

ORAL TABLET MEDICATION ..................................................................................................................................................146

MAKING THE MOST OF YOUR REPTILE VETERINARIAN.........146

SPECIESLARGE TERRESTRIAL AND ARBOREAL MONITORSPRONUNCIATION .....................................................................................................................................................................................149

DESCRIPTION ..............................................................................................................................................................................150

ADULTS, JUVENILES, SEXING, SUBSPECIES ............................................................................................150

IN THE WILD .....................................................................................................................................................................................158

DISTRIBUTION AND HABITAT ...........................................................................................................................................158

IN CAPTIVITY ...............................................................................................................................................................................160

STATUS ........................................................................................................................................................................................................................160

HOUSING .......................................................................................................................................................................................................160 INDOOR ENCLOSURES ....................................................................................................................................................................160 Summary ...................................................................................................................................................................................................................163

OUTDOOR ENCLOSURES ............................................................................................................................................................163

COMPATIBILITY ...........................................................................................................................................................................................164

FEEDING ..........................................................................................................................................................................................................165

BREEDING....................................................................................................................................................................................................166

INCUBATION AND HATCHLING DEVELOPMENT ..............................................................................169

BREEDING RECORDS FOR LARGE TERRESTRIAL AND ARBOREAL MONITOR SPECIES ......................................................................................................................................170

HYBRIDISATION AND COLOUR VARIANTS .................................................................................................170

LONGEVITY .........................................................................................................................................................................................................172

ACKNOWLEDGEMENTS ................................................................................................................................................................172

ROCK MONITORSPRONUNCIATION .....................................................................................................................................................................................173

DESCRIPTION ..............................................................................................................................................................................173


IN THE WILD .....................................................................................................................................................................................177


IN CAPTIVITY ...............................................................................................................................................................................178

STATUS ........................................................................................................................................................................................................................178



COMPATIBILITY ...........................................................................................................................................................................................181

FEEDING ..........................................................................................................................................................................................................181

BREEDING....................................................................................................................................................................................................182INCUBATION AND HATCHLING DEVELOPMENT ..............................................................................185BREEDING RECORDS FOR ROCK MONITOR SPECIES .............................................................186HYBRIDISATION AND COLOUR VARIANTS .................................................................................................186LONGEVITY .........................................................................................................................................................................................................186ACKNOWLEDGEMENTS ................................................................................................................................................................186

SMALL TERRESTRIAL MONITORSPRONUNCIATION .....................................................................................................................................................................................187

DESCRIPTION ..............................................................................................................................................................................187


IN THE WILD .....................................................................................................................................................................................196


IN CAPTIVITY ...............................................................................................................................................................................198STATUS ........................................................................................................................................................................................................................198

HOUSING .......................................................................................................................................................................................................198 INDOOR ENCLOSURES .................................................................................................................................................................. 198 Summary ...................................................................................................................................................................................................................200

OUTDOOR ENCLOSURES ............................................................................................................................................................200 COMPATIBILITY ...........................................................................................................................................................................................201FEEDING ..........................................................................................................................................................................................................201

BREEDING....................................................................................................................................................................................................202INCUBATION AND HATCHLING DEVELOPMENT ..............................................................................205

BREEDING RECORDS FOR SMALL TERRESTRIAL MONITOR SPECIES .......205HYBRIDISATION AND COLOUR VARIANTS .................................................................................................206LONGEVITY .........................................................................................................................................................................................................206ACKNOWLEDGEMENTS ................................................................................................................................................................206

SMALL TO MEDIUM ARBOREAL MONITORSPRONUNCIATION .....................................................................................................................................................................................207

DESCRIPTION ..............................................................................................................................................................................207


IN THE WILD .....................................................................................................................................................................................221


IN CAPTIVITY ...............................................................................................................................................................................224

STATUS ........................................................................................................................................................................................................................224



COMPATIBILITY ...........................................................................................................................................................................................227

FEEDING ..........................................................................................................................................................................................................228

BREEDING....................................................................................................................................................................................................229INCUBATION AND HATCHLING DEVELOPMENT ..............................................................................230BREEDING RECORDS FOR SMALL TO MEDIUM ARBOREAL MONITOR SPECIES ...............................................................................................................................................................................231HYBRIDISATION AND COLOUR VARIANTS .................................................................................................232LONGEVITY .........................................................................................................................................................................................................232ACKNOWLEDGEMENTS ................................................................................................................................................................232

WATER MONITORSPRONUNCIATION .....................................................................................................................................................................................233

DESCRIPTION ..............................................................................................................................................................................233


IN THE WILD .....................................................................................................................................................................................241


IN CAPTIVITY ...............................................................................................................................................................................244

STATUS ........................................................................................................................................................................................................................244



COMPATIBILITY ...........................................................................................................................................................................................248

FEEDING ..........................................................................................................................................................................................................248

BREEDING....................................................................................................................................................................................................249INCUBATION AND HATCHLING DEVELOPMENT ..............................................................................251BREEDING RECORDS FOR WATER MONITOR SPECIES .........................................................252HYBRIDISATION AND COLOUR VARIANTS .................................................................................................253LONGEVITY .........................................................................................................................................................................................................253ACKNOWLEDGEMENTS ................................................................................................................................................................253

AUSTRALIAN HERPETOLOGICAL SOCIETIES AND USEFUL WEBSITESHERPETOLOGICAL SOCIETIES ..........................................................................................................................................254OTHER USEFUL WEBSITES .......................................................................................................................................................255

BIBLIOGRAPHYPRINTED LITERATURE......................................................................................................................................................................255ONLINE RESOURCES ..........................................................................................................................................................................258

GLOSSARY .....................................................................................................................................................................................259

Varanus brevicauda

S EI

PPER

Timber Enclosures These python-style enclosures feature five solid sides and a glass or mesh front. Timber enclosures are secure, accessible, aesthetically pleasing, easy to supply light and heat to and may be purchased commercially or be homemade.

They are suitable for accommodating terrestrial and arboreal species, depending on furniture placement. Their suitability as arboreal enclosures can be improved by decorating the rear and side walls with mock rock or by firmly attached furnishings.

The main disadvantages of timber enclosures are that they are expensive, difficult to ventilate, prone to overheating, heavy and are generally only suitable for dry furnishings—sealed timber and melamine will eventually succumb to water damage.

Glass, Perspex or Plastic Moulded Commercial Terrariums Increasing in popularity and availability, these enclosures feature three to four solid sides and one to two mesh sides—or two sides made of half mesh—and a glass front door.

Glass terrariums are secure—although some small arboreal monitors can secrete themselves into very narrow gaps, few adults lizards have narrow enough heads to escape from standard glass doors or narrow ventilation gaps. They are also durable, available in standard sizes allowing for standard shelving, and are easily made aesthetically appealing—some include mock rock backgrounds as a standard fitting.

Melamine enclosures with sliding glass frontsC

GU

EST

Commercial glass terrariums are ideal for small terrestrial species

Moulded plastic terrariums with modified wire fronts are used in the author’s collection for small arboreal species

D B

ROW

N

D B

ROW

N

can be difficult. Use electrical mounting blocks secured by a silicone sealant suitable for aquarium manufacture to the glass enclosure walls. This supports the actual light fitting and accommodates the wiring. Improve the stability of these attached mounting blocks by marking

the base of the mounting block with several small holes or scratches to give the silicone something to grip to. These mounting blocks then become the base upon which you attach a lamp fitting. I recommend using adjustable light sockets that can be directed downwards at a 45 degree angle. Alternatively, a simple angle bracket constructed from galvanised steel or aluminium can be stuck to the glass using silicone or double-sided tape. This acts as a base upon which a ‘clamp lamp’ can be attached. IKEATM sells a wonderful range of ‘clamp lamps’.

• Position heat lamps towards one end of the enclosure to allow a heat gradient to be established and to encourage air flow from one area to another.

• Use in line dimming units such as the IKEA DimmaTM in small enclosures to regulate maximum temperatures and avoid overheating.

D B

ROW

N

D B

ROW

N

Reptile infrared lamp

Sunlight and moonlight replicating reptile lamps

This commercial IKEA™ ‘clamp lamp’ is ideal for small hatchlings

Use a mounting block to attach a lamp to a glass surface

D B

ROW

N

D B

ROW

N

VERTEBRATE FOOD ITEMSVirtually all reptile families include at least one species that feeds on vertebrate food items such as rats, mice, chicks, quail, guinea pigs, small birds, fish and other lizards.

Monitors will accept almost any type of vertebrate prey, consuming almost anything physically possible. Most will consume mice, rats, chicks, guinea pigs, small birds—such as sparrows, quail and finches—and fish. Few species seem to be particularly fussy. Small hatchlings will accept chopped pinkie mice and small fish.

Avoid feeding large items or large meals to large specimens. Although they may be able to physically eat the meal, many may regurgitate it afterwards. Feeding to 80% of swallowing capacity is more acceptable.

Vertebrate food items have various features to be aware of.

Rats and Mice These vertebrate food items can be fed to a range of lizard species at every life stage. Generally, smaller life stages of mammalian prey such as pinkies, fuzzies and weaners are more nutritionally suitable than larger life stages, which often carry higher levels of fat and lower levels of protein.

A lizard’s ability to digest rats and mice improves when multiple, small items are fed—rather than single, large items with a greater surface area to digest. Some keepers believe multiple, small items are less nutritional as they may possess more indigestible hair than a large item—studies have disproved this theory.

Mice and rats should be fed a quality commercial diet designed for laboratory rats and mice. Cutting corners will alter their nutritional value and usually increase their fat content.

Feeding pinkie mice and rats that have a full stomach of milk is equivalent to gut loading with calcium, due to the high calcium component of the mother mouse’s milk. This increases the calcium to phosphorus ratio to the equivalent of an older juvenile with more mineralised bones.

Mouse sizes (left to right)—large adult, regular adult, weaner, hopper, fuzzie and pinkie

D B

ROW

NJ

SEIJ

DEL

Varanus indicus feeding on a rat

BREEDINGVISUAL SEXINGThe correct identification of gender is the first step towards breeding success. For many species, this process is simple—for others it requires educated guesswork.

There are various methods of sexing lizards, which range in complexity and reliability. Visual sexing is one of the most common methods and involves the examination of a lizard’s secondary sexual characteristics including colour, size, pore structures, hemipenal bulges and paracloacal spur structures.

Following is an outline of each method. For more specific details of distinguishing features in each species refer to the individual species chapters.

ColourMany lizard species display considerable sexual dimorphism with regard to colour patterns in particular. Colour differences are noted among some species of monitors but are limited primarily to differences in overall brightness or throat coloration.

This male Varanus ‘kuranda’ displays brighter ocelli and a bright yellow throat

This female Varanus ‘kuranda’ displays duller body and throat colour

S M

ACD

ON

ALD

G S

CHM

IDA

Determining Egg Viability There is little benefit incubating eggs that have no likelihood of hatching. Therefore, it is important to be able to identify which eggs are viable—of adequate quality and fertility. Viability should be assessed pre-incubation at the time of collection, and post-incubation for 10−20 days following incubation. Pre-incubation indicators of non-viable eggs are—Yellowish coloured eggsGood quality eggs are generally a clean, white colour.Sunken eggsParticularly if other eggs in the clutch appear normal.Soft and squishy eggsEggs that indent easily may indicate drying or non-viability. FirmnessViable eggs are generally plump and slightly compressible like a well inflated balloon. Eggs that are hard are often referred to as ‘slugs’ and are infertile, non-viable eggs.Adherence of substrateWhile it may be quite normal for the eggs of some species to have substrate stuck to the eggs, it should be consistent throughout the whole clutch. Different sized eggs in one clutchSignificant differences in the size of eggs within a single clutch may indicate some eggs—generally the smaller ones—are non-viable.

Sorting good eggs from bad is generally simple. However, if there is any doubt, suspect eggs should be incubated anyway. Equally, not every egg that appears viable will stay that way. Eggs that appear healthy initially may still fail if the embryo does not develop or dies. Most non-viable eggs that initially appear healthy will fail the first 7−14 days after incubation.

D B

ROW

N

D B

ROW

N

‘Pink side up’—the pink side represents the embryonic side. This should be placed upwards in the incubation container

The yellow side of the egg represents the yolk side. This should be placed downwards in the incubation container

A freshly laid, healthy, plump, clean Varanus gilleni egg being candled—note the germinal ring

Infertile ‘slugs’ from a Varanus storri

D B

ROW

ND

BRO

WN

Treatment can involve the use of medication. However, this medication should be targeted precisely at the parasite involved, which can only be determined through the analysis of faecal samples. Medication should be targeted in this way rather than by ‘shotgun’ medication.

There are many commercial antiparasitic products available, but few are designed for reptiles. Each lizard group may vary in its reactions to medication—a safe drug in a dragon may potentially be toxic to a monitor and vice versa. Therefore, it is unsafe for me to record dose rates here. Consult your reptile veterinarian for their preferred medication regime.

Treatment may also require de-stocking and decontamination to prevent reinfection—particularly with coccidial and pinworm infections.

EXTERNAL PARASITESTicks and mites are the two main external parasites occasionally found on lizards. Ticks are generally only found on specimens housed outdoors, although it is possible that tick larvae may be transported on leaf litter into an indoor enclosure. These large, blood-sucking parasites are more unsightly than dangerous. However, due to problems associated with the toxicity of acaricidal drugs, it is best to remove them as soon as they are observed. Simply grip the tick between your fingers, or with forceps, and employ a twisting and pulling motion to remove them.

Mites which cause clinical disease are a limited problem to lizards. Although lizards may be inhabited by mite species, they are rarely infected by the snake mite Ophionyssus, although this has been observed on rare occasion on pygopods—particularly Lialis burtonis—and on larger skinks such as Tiliqua species. This could be because these lizards have a similar scale pattern to snakes compared to a monitor’s scales.

Treatment methods include smothering the mites with spray-on kitchen oils. Alternatively, chemical treatments such as ivermectin-based sprays may be used on dragons, skinks and monitors—avoid the head and wash the spray off after 15 minutes. Consult your reptile veterinarian for appropriate dose rates.

Non-pathogenic mites commonly affect lizards. These small, red mites target eye sockets, armpits and groin areas and occur when lizards are housed outdoors or if an enclosure’s furnishings are sourced from where the mites naturally occur.

D B

ROW

N

Multiple ticks on a Varanus giganteus

AN

ON

Non-pathogenic red mites in the groin area of Varanus ‘scalaris’

JUVENILESHatchlings are a brighter version of the adult, particularly Kimberley Rock Monitors V. glauerti. They are generally 25−40% of adult size. Adult colouration develops at 3−4 months of age and individuals reach full adult colouration at 50−70% of adult SVL.

SEXING Rock monitors should be sexed using a combination of methods.

Visually, males are generally larger than females of the same age and have a broader, more robust head and body.

The male spur clusters differ from that of the female. They are similar to that of the Black-headed Monitor Varanus tristis and are located at the base of the tail above the vent. The clusters comprise approximately 10−12 roughly oval-shaped, conical scales that are smaller at the perimeter and larger in the centre, forming a small, spiky mound. In males, the largest scales are 2−4 times the size of the adjacent scales, whereas females’ largest scales are only 1−1.5 times the size of the adjacent body scales. Males also have a greater number of larger scales per cluster than females.

The spur scales of the Kimberley Rock Monitor V. glauerti are often chocolate brown or grey and creamy white in colouration. In the Pilbara Rock Monitor V. pilbarensis they are flatter, fan-shaped and the individual spur components are larger and more numerous in males than in females.

When sexing using paracloacal spurs, be aware that spur clusters are larger during the breeding season due to an increase in the thickness of the keratin layer over the spur scales at this time.

Radiography of the tail base of adult males will reveal the presence of calcifications of the support structures of the hemipenes, referred to as ossified hemibacula. These structures are absent in adult females, but present among males of all species in this group. It is not known at what average age the hemipenal support structures develop calcification. I have not personally had the opportunity to examine radiographs of any of these species, but I have observed calcifications in most male monitors at proportions equivalent to 60−70% of adult SVL—this should be considered the smallest size for this technique to be considered reliable. The presence of ossifications from this age onwards indicates a male, however

K PA

TAN

AN

TK

PATA

NA

NT

Varanus glauerti hatchlingsB

VAN

AST

EN

Varanus pilbarensis hatchling

Leucistic form (left) and Normal V. kingorum hatchlings

AN

ON

SMALL TERRESTRIAL MONITORSThe small terrestrial monitor group comprises six species as follows—Ridge-tailed Monitor or Spiny-tailed Monitor Varanus acanthurus Black Spotted Spiny-tailed Monitor, White’s Monitor or Lemon-throated Monitor Varanus baritji Storr’s Monitor Varanus storriNorthern Blunt Spined Monitor or Northern Ridge-tailed Monitor Varanus primordius Short-tailed Pygmy Monitor or Short-tailed Monitor Varanus brevicauda Pygmy Desert Monitor or Rusty Desert Monitor Varanus eremius

PRONUNCIATION Following are the accepted pronunciations of the six small terrestrial monitor species—Varanus acanthurus Varr-ann-us ack-an-thoo-rusVaranus baritji Varr-ann-us bah-rit-jeeVaranus storri Varr-ann-us store-eeVaranus primordius Varr-ann-us pry-more-dee-usVaranus brevicauda Varr-ann-us brev-ee-cord-ahVaranus eremius Varr-ann-us er-em-ee-us

DESCRIPTIONADULTS The majority of the small terrestrial monitors fall into a group known as spiny-tailed monitors—so called due to the heavy scalation on their tails, which are robust, round in cross section and display sharp backward pointing spines. They have a sharp, pointed snout, long bodies and tails varying from 80−200% of their body length.

G G

AIK

HO

RST

Varanus acanthurus

Suitable substrate is sand at a depth of 100−150mm to allow for digging although species including the Pygmy Desert Monitor V. eremius and the Short-tailed Pygmy Monitor V. brevicauda will appreciate substrate to a depth of at approximately 250mm.

‘Monitor stacks’ made from separated layers of plywood or tiles, mimic layers of exfoliating rocks and provide shelter and basking sites. These layers should be separated using 20−25mm timber slats firmly anchored to the plywood so they don’t collapse. A terracotta or slate tile placed on the top level will reduce the fire risk associated with heated timber. The basking lamp should be directed on to the top of the vertical stacks to create a vertical heat gradient. Some keepers also place a heat pad at the bottom of the stack.

Alternatively, the enclosure may be decorated with rock slabs, solid branches, terracotta tiles or roof tiles. All structures must be placed directly onto the enclosure floor to prevent collapse—monitors regularly dig at the base of structures, undermining their stability. Vegetation is not recommended as it is usually destroyed by monitor digging behaviour.

Species including the Pygmy Desert Monitor V. eremius and the Short-tailed Pygmy Monitor V. brevicauda may be provided with a flat tile laid directly on the sand surface under the heat lamp to allow for burrowing behaviour at the same time as subsoil and surface basking. Glue short timber legs onto these tiles to ensure they always remain above the enclosure floor even if the sand is dug out underneath.

Alternatively, place the tile or timber stack on top of a wide flat tray, such as a cat litter tray, filled to the top with moist sand. This will allow for burrowing behaviour, surface and subsoil basking and provide a potential nesting site with a heat gradient. It also allows much more control over soil moisture levels. Access to this area can be provided by a single hole in the surface tile.

Small terrestrial monitors originate from hot environments and require high environmental temperatures. A basking temperature of 40oC−70oC with a heat gradient of 28oC−35oC in the remainder of the enclosure is ideal. Although these temperatures might seem extreme, these small monitors thrive on it. Cooler temperatures will also be present within enclosure burrows.

Heat should be provided for at least 14 hours daily during summer and for 4–6 hours daily during winter. Heating time can be gradually reduced from mid-autumn by 30–60 minutes each week. This heating regimen allows the occupants to bask if they need and spend most of the day in ambient winter conditions. I believe this is important for small species with high metabolic rates—less post cooling problems are noted than if no heat is provided at all.

Alternatively, some keepers provide 8–10 hours of heating daily over the entire winter period with a 10oC drop in the heat gradient and basking temperature across the entire enclosure.

In environments similar to their natural temperature range, heating may be turned off in winter and visible light utilised to mimic the photoperiod.

D B

ROW

N

Components of a suitable enclosure

Sneak preview of A Guide to Australian Monitors in Captivity

Documents

Transcript of Sneak preview of A Guide to Australian Monitors in Captivity