FINAL RE PORT

Satellite (IRLS) Tracking of Elk

Contract NASW-1983

Helmut K. BuechnerSenior EcologistSmithsonian InstitutionWashington, D. C. 20560October 11, 1972

The objective of tracking an animal on the surface of theearth by satellite, using the Interogation Recording LocationSystem (IRLS), was accomplished during the eighteen monthperiod of the contract (November 5, 1969 to May 4, 1971).Details of the experiment are presented in the enclosed reprintof "Satellite and Ground Radiotracking of Elk"''t>y Craighead, etal. (1972), and the larger implications of satellite tracking inecological studies are discussed in the enclosed reprint of"Satellites for Research on Free-Roaming Animals"*by Buechner,et. al. (1971).

The experiment with the elk was a qualified success inthat the animal was tracked only on the National Elk Refuge inWyoming and the IRLS collar inverted at the onset of springmigration, losing contact with the satellite when the antennapointed groundward. However, the elk was tracked for 30 daysand 9 channels of the IRLS system were used to transmit datafrom the instrument collar to the satellite, including the elk'ssurface body temperature, ambient temperature, length of the"window" during which the satellite was in radio view of the elk,light intensity, and battery strength. The study also showed thatthe weight of the collar (11.3 kg) was readily carried by the elkwithout skin abrasions or observable behavioral or physiologicalstress. When the elk was inadvertently shot by hunters who didnot see the collar, which was concealed by the underbrush, theanimal had normal storages of fat for the fall season and it waspregnant.

A reduction in weight of the collar by about 50% wascalculated from the data derived from the experiment, mostlyin saving on batteries since the solar-panel system functionedexceedingly well. A new IRLS collar was designed andstruction was nearly completed when

* = Reprint attached

https://ntrs.nasa.gov/search.jsp?R=19730006363 2020-03-25T15:54:49+00:00Z

-2-

official at NASA that a second elk experiment would not bepermitted.

This decision was based on fear of adverse publicityshould the elk die or the collar invert. The first elk that hadbeen immobilized and instrumented died within 2 days andbrought forth a flow of letters to NASA, the SmithsonianInstitution, the U.S. Bureau of Sports Fisheries and Wildlife,and to congressmen.

The IRLS system proved to be a highly effective two-waycommunications system for interrogating physiological and en-vironmental parameters while tracking an animal in its naturalenvironment. The system can serve as a valuable tool forinvestigating basic biological problems on animals that cancarry the weight of the instrument, and it is especially applicablefor animals that travel great distances in remote, inaccessibleareas of the world.

The tracking of the elk represented the first time ananimal has ever been tracked on the surface of the earth bysatellite. Had it not been for the adverse publicity encountered,the significance of the experiment and public acceptance of theIRLS system as a research tool would have led more rapidlytoward further development of satellite systems for trackingand monitoring free-roaming animals.

Satellite and Ground Radiotracking of Elk

FRANK C. CRAIGHEAD, JR.JOHN J. CRAIGHEAD

CHARLES E. COTEHELMUT K. BUECHNER

Smithsonian Institution

R ADIOTRACKING AND MONITORING offree-living animals in natural environ-

ments is providing an effective new techniquefor acquiring information on biological proc-esses, including animal orientation and navi-gation. To test the practicability of extendingthe technique by using satellite systems fortracking animals, a female elk was instru-mented with an electronic collar. It con-tained both the Interrogation Recording Lo-cation System (IRLS) transponder and aCraighead-Varney ground-tracking trans-mitter. The elk was successfully trackedand monitored by satellite during the monthof April 1970. This was the first time ananimal had been tracked by satellite on thesurface of the Earth; Information derivedfrom the present feasibility study provides abasis for assessing uses of the system, reducingthe weight, and improving the configurationof the instrument collar for monitoring a va-riety of large mammals. The minimumweight of the IRLS transponder, even withmicrominiaturization, makes its use impracti-cal for most small mammals and birds. Adoppler-shift type of satellite system, as de-

scribed by Maxwell at this conference, mayprove effective for small animals.

This project was a joint endeavor be-tween the Smithsonian Institution and theNational Aeronautics and Space Administra-:tion, conducted in collaboration with theMontana Cooperative Wildlife ResearchUnit, the Environmental Research Institute,the State University of New York at Albany,and the National Geographic Society. Pre-testing was conducted at the National BisonRange, Moiese, Montana. The experimentwas carried out at the National Elk Refuge,Jackson Hole, Wyoming, in cooperation withthe U.S. Bureau of Sports Fisheries and Wild-life, the Wyoming Game and Fish Commis-sion, the U.S. Forest Service, and the Na-tional Park Service. Previous research underNSF (G-17502) made possible the use of theground radiotracking system.

HISTORY OF PROJECT

The present project had its inception onMay 26, 1966, at a conference sponsoredjointly by the Smithsonian Institution, the

99

100 A N I M A L O R I E N T A T I O N A N D N A V I G A T I O N

American Institute of Biological Sciences,and the National Aeronautics and Space Ad-ministration (ref. 1). At this time the possi-bilities for using the Nimbus meteorologicalsatellites for tracking and monitoring wildanimals were explored by biologists and engi-neers. An initial estimate of 11.3 kg for theIRLS instrument platform proved accu-rate. This transponder was heavy for use onwild animals, as it had been designed foroceanographic buoys and high-altitudeweather balloons. It was apparent that alarge animal would be required for the firstexperiments in satellite tracking of free-roam-ing animals. However, engineers calculatedthat the weight could eventually be reducedby 50 to 75 percent. An elk was chosen forthe first test because of its large size (about225 kg), gentleness, and migratory behavior.In addition an accumulated background ofexperience in radiotracking and immobilizingelk (ref. 2) was available over a period ofyears in the Jackson Hole-Yellowstone Na-tional Park area. Logistic support for •- theproject was particularly favorable in theJackson Hole area.

A planning conference was held May 9—12, 1969, in Missoula, Montana, at whichtime biologists and engineers decided on theconfiguration and packaging of the IRLStransponder and selected parameters to bemonitored. A Craighead-Varney transmitterwas packaged with the IRLS transpondersince this ground-tracking system had a capa-bility that enabled observers to visually locatethe elk, thus providing direct observationswith which to measure the accuracy of satel-lite positioning. This 32.0 MHz tracking sys-tem had been used to successfully track sixcow elk for a total of 1216 animal trackingdays. In addition, one elk had been radio-tracked from the National Elk Refuge to itssummer range in Yellowstone National Park,a distance of 64.4 airline km.

PROJECTIONON

EARTH

AMBIGUOUS POSITION PLATFORM POSITION

FIGURE 1. IRLS location technique: Distance(Rt) between satellite and instrument platformgenerates a sphere with satellite at center (I\):this sphere in space intersects the Earth in aperfect circle. Second perfect circle intersectingfirst at two points is formed by second interroga-tion at T2. Platform position is readily selected onbasis of prior information from previous orbits.

MATERIALS AND METHODS

The experiment was carried out with theNimbus III and IV satellites, using the IRLSsystem to locate and interrogate the animals(refs. 3 to 5). The IRLS instrument wasdesigned with 28 channels of communication,10 of which were used in the present experi-ment. One IRLS instrument was modifiedand packaged into the collar for the elk, withbatteries as the source of power and solarcells to maintain battery charge. To conservepower, a timing system provided a 10-minwindow for transmission during satellite over-passes. The radio transmitter power outputwas 15 W to the antenna at a frequency of466.0 MHz.

The Nimbus satellites are in polar-sun-synchronous orbits, and their exact positionabove the Earth can be calculated. Thedistance between the satellite and elk wasdetermined by a radar-like interrogation.This line generates a sphere, with the satelliteat the center, that forms a perfect circlewhere it intersects the Earth's surface. An-

S E S S I O N I I : A N I M A L T R A C K I N G 101

other circle is formed by the second interro-gation, intersecting the first circle at 'twopoints. The animal is located at one of thesetwo points; the other point is sufficiently dis-tant from the animal, as determined by priorinformation, to be considered unlikely as theanimal's position (fig. 1).

The Craighead-Varney ground-trackingtransmitter (32 MHz) was installed in thelower compartment of the collar. Batteriesand antenna for this system were located atthe top of the collar.

The instrument collar was separable intotwo parts for installation on the elk. Instru-menting was accomplished when the animalwas immobilized with M99 (etorphine). Tenmin were required to make the electronicconnections and fasten the collar on the elk.

Internal telemetry for the instrument wasprovided by five sensors, and external datawere monitored by another five sensors. Thedata format corresponding to the computerprintout is shown in figure 2. One such frameof data was collected during each interroga-tion of the instrument. For each overpass thesatellite was programmed for up to five inter-rogations at intervals of 1.5 min. Data wereavailable to the experimenters within 1 to 2hr of the overpass. The pressure transducerfor measuring altitude failed and was inoper-ative throughout the experiment. Skin tem-perature was measured by a thermistormounted on a tension arm attached on theinside surface of the collar. Battery voltagesand temperatures were monitored directly,and the received signal strength was obtainedat the output of the first intermediate fre-quency stage. Two thermistors provided over-lapping scales (—40 to + 10 °C; 0 to -j-50 °C) for measuring ambient temperaturewithin ± 1 percent accuracy. For additionalinformation about the IRLS system see Craig-head et al.

An electromechanical timer-control unit

DATE OF RUN MO. DAY

4 28

ORBIT NUMBER 5082

PLATFORM ID 105452

COMMAND TIME HH MM SS.5

07 54 10.6

FRAME 1

DATA RECEIVED

YR.

70

2 UNUSED

4 ALTIMETER

6 *12 VOLT BATTERY

8 BATTERY TEMPERATURE10 -40 TO +10'C AMBIENT

12 TIMER

! ) UNUSED28 '

1 UNUSED3 UNUSED

5 RECEIVER SIGNAL

7 SKIN TEMPERATURE9 0 TO *50'C AMBIENT

11 »4.8 VOLT BATTERY13 LIGHT INTENSITY

1 } UNUSED

COMPUTED PLATFORM LOCATION

TIMELAT.

43.492N

LONG.

H0.721YI

DAY

118

SS.S

11.0

FIGURE 2. Data format showing arrangementof data on computer printout forms.

provided a 6-month battery lifetime by com-pletely unloading the battery during the 12-hr intervals between orbital overpasses. Dur-ing each overpass a 10-min "power on" pe-riod was initiated precisely as the satellitecame into radio view. The timer setting ofthe window was monitored on each orbit,and periodic adjustments were made by com-mand from the satellite to maintain syn-chrony.

PROCEDURE

During the summer and fall of 1969 amockup model of the instrument collar wasdeveloped and tested on four female elk in acorral at the National Bison Range. The col-lar (11.3 kg) weighed less than knownweights of elk antlers. None of the elk experi-enced any apparent interference with dailyactivities, and there was no evidence ofbreakage of hair or skin abrasions from rub-bing of the collar during feeding activities.One elk carried the collar for a period of 90days without difficulty. Pretesting of the elec-tronic instrument collar began on January

102 A N I M A L O R I E N T A T I O N A N D N A V I G A T I O N

20, 1970, using the same female elk after ithad been without the mockup collar forabout 2 weeks. The pretest was highly suc-cessful in terms of placing the instrument col-lar on the elk and interrogating the instru-ment daily for the next 12 days on 16 orbitsof the satellite.

On February 5, two female elk at theNational Elk Refuge were immobilized andfitted with mockup collars to pretest the reac-tion of these animals to the collar prior toinstrumentation.

On February 19, an effort was made toplace the IRLS collar on one of the twofemales wearing the mockup collars. The elkwere uneasy as a result of a census of theherd made earlier that morning, and the ex-perimental animal was difficult to approach.Considerable maneuvering was required toget one of the females within range of theimmobilizing gun. The shot made at longrange (60 to 70 m) missed the intended elkand struck another female in the herd. Shebecame immobile in about 5 min. This fe-male appeared to be a healthy individual, andexcept for preconditioning to the collar,equally well suited for the experiment as ei-ther of the females wearing mockup collars.Since conditioning did not appear to be es-sential, the instrument collar was fastened tothis elk with the assistance of electronic engi-neers. The female recovered quickly upon re-ceiving the antidote M285 (diprenorphine)after being immobile for 30 min. The femalethen rose to its feet without difficulty, stoodmomentarily looking at the haywagons andobservers without apparent alarm, and thenran to rejoin the herd. The satellite was un-able to communicate with the instrument col-lar for. the first 3 days, apparently becauseinstallation of the instrument package hadoccurred during the hourly 6-min speed-upcycle, \vhich in turn disrupted the orbital pe-riod setting of the timer. By special command

from the satellite the timer was reset, and atnoon on February 22, data were receivedfrom the animal. Subsequent passes failed toyield data. Visual observations of the elkindicated that she remained bedded down forabnormally long periods of time, walkedsluggishly, and was not feeding. The femalefinally died on the morning of February 23,apparently of pneumonia which is not un-common in the herd on the Refuge. Thestress of being captured may have aggravatedan incipient infection.

On April 1, 1970, one of the two femalesoriginally fitted with a mockup collar wasinstrumented with the IRLS equipment (fig.3). A veterinarian ascertained the health ofthe animal. Her body temperature was nor-mal (38.5 °C) and she appeared to be ingood condition. She became immobile 5 minafter administration of the M99 drug andremained immobile for about 27 min, duringwhich time the dummy collar was removedand the electronic collar was attached. Im-mediately after the antidote was injected the

FIGURE 3. IRLS instrument collar on female elktracked in April 1970. Antenna housing is attop and solar panels are on side of collar.

S E S S I O N I I : A N I M A L T R A C K I N G 103

43'29'00"N110'36'00"W>

FIGURE 4. Locations of instrumented elk fromdirect observation or fixes with Craighead-Vameyground-tracking system. Accuracies were within0.5 km. Errors in satellite fixes were computedagainst these observations. Arrows indicate direc-tion of following observation.

female was placed on her brisket. Within 3minutes she arose, looked around briefly atthe observers and then nibbled at a nearbybale of hay. The instrumented female thenwalked off about 25 rn, stopped, and thenslowly ran off to join the herd about 200 maway. When she joined the herd she immedi-ately had an encoutner with another female.Both elk rose on their hind legs and paddledgently with their forelegs. Such behaviorseems to establish dominance-subdominancerelationships between individuals within theherd. This incident and the immediate ac-ceptance of the instrumented elk by othermembers of the herd indicated that the proc-ess of immobilizing and instrumenting hadnot been traumatic and that the female re-turned to normal behavior almost immedi-ately after recovering from the drug. Withinthe next hour the instrumented female wasobserved feeding, standing, and walkingwith the herd.

The elk had recovered and joined the

FIGURE 5. Visual observations vs satellitepositions.

herd by 10:50 a.m. At approximately 11:00a.m., Nimbus III passed over the JacksonHole area and the IRLS collar transmittedlocation, skin and air temperatures, and fiveparameters of the IRLS instrument (table1).

RESULTS

The resolution of locations determined bythe satellite varied considerably. In order tomeasure the accuracy of the locations it wasnecessary to derive a set of reference pointsfrom field observations of the elk. Orbitaloverpasses were approximately at noon, andsome of the observation times did not coin-cide exactly with satellite overpasses, makingsome interpolation necessary in deriving theset of reference points. The reference pointsmade on the ground are shown in figure 4.The magnitude and direction of location er-rors "determined by satellite are shown infigure 5. Three locations were beyond thescale and were not included in the figure.Excluding these three points the mean errorswere 4.8 km in latitude and 6.2 km in longi-tude. The large east-west errors (longitude),which were typically less than the north-south errors (latitude), reflected the fact that

104 A N I M A L O R I E N T A T I O N A N D N A V I G A T I O N

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FIGURE 6. Satellite monitored day-nightbattery voltages and temperatures.

satellite locations are most accurate when thesatellite is between 10 and 50° above hori-zontal. The dipole antenna used in the elkexperiment was designed for a coverage above45° with respect to the horizontal. In futureexperiments the accuracy of locations can be

i,improved with a low profile, omnidirectional,circularly polarized antenna.

The monitoring of sensors showed the po-tentialities of the IRLS system for obtainingphysiological and environmental information(table 1). The voltage levels of the batteriesincreased during the first 3 days, showingthat the solar panels were responsible forcharging the batteries. The charge levels re-mained near maximum throughout the exper-iment. The trends in battery and ambienttemperatures were identical (fig. 6). Somewarming was probably provided by the elk'sbody. In previous studies of the effects ofambient air temperature on radio collars thebattery pack1 and transmitter have shown anaverage 9.4° C increase over air temperaturesunder cold weather conditions. This was at-

tributed to the warming effect of the animal'sbody (refs. 6 and 7).

The accuracy of measuring skin tempera-ture with a thermistor at the point of contactbetween the collar and the animal's body re-quires further testing to determine the effectsof the collar in compacting the hair and insu-lating the thermistor, as well as the effect ofmovement of the collar during feeding activ-ity. Individual skin readings taken at 1.5-minintervals during interrogation sequences sug-gest that the animal was at rest when thereadings were constant and active when thereadings were variable (table 2). Apparentlymovement of the collar altered its insulatingeffect, producing more regular temperaturereadings when the elk was at rest. The excep-tionally high skin temperature (37.5° C),which was near body temperature, on April10 could have resulted from continued pres-sure of the elk's neck against the thermistoras the animal lay on its side with its neckresting on the collar. In a similar manner askin temperature of 35.9° C was recordedfrom an awakened and alert black bear in itswinter den as it lay on a thermistor located

TABLE 2.—Multiple Interrogation Skin Data

April 9, night. . .

'

April 17, night. .•

April 21, night. .

Elk atrestCC)

23.623.6.23I.323,023.028.028:328 ."328.325.025.525.5

April 7, night.

April 9, day. . .

April 23, day. .

Elkmov-ing

18.620.520.319.727.827.228.123.030.930.030.329.9

S E S S I O N I I : A N I M A L T R A C K I N G 107

between the animal's body and the insulatingmaterial of its bed (ref. 2). An inverse rela-tionship between skin and ambient tempera-tures, shown in about half the recordings(fig. 7), could reflect a decrease in insulationof the elk's integument due to compaction ofthe hair under the collar. The significance ofthe data is that they show the potentialitiesfor studying thermoregulation by monitoringsurface and subcutaneous skin temperature,along with deep body temperature, using theIRLS system.

MOVEMENTS OF THE ELK

Except for the longer movements, the lo-cations obtained with the IRLS system weretoo inaccurate for determining the local pat-tern of movement of the elk within the Ref-uge. However, satellite location of the elkcould have yielded useful new information onmigratory movements despite the low resol-ution. The collar rotated around the elk'sneck on May 1 and, in the inverted position,contact between the elk and the satellite waslost. Communication proved impossible withthe antenna pointing groundward. UntilJune 10, the elk was located by the ground-tracking system. When the elk moved far orrapidly it was relocated by air, using a Cessna150 with a small loop antenna attached tothe wing strut. Under favorable conditionsthe signal was received in the airplane from adistance of up to 40 km at altitudes aboveground level of 300 to 1000 m; the strengthof the signals improved with altitude.

. On May 15, the elk moved to the northernportion of the Refuge and was approached,using the directional receiver. She was ob-served to feed and run well with a band of15 elk, and she appeared in better physicalcondition than most of the other elk. Twodays later she left the Refuge, moved northalong the east side of Blacktail Butte, and

FIGURE 7. Satellite monitored skin and ambienttemperature readings.

arrived the following day in the area of Sig-nal Mountain, 28 airline km from her lastposition in the Refuge. After remaining hereand in this general area for 5 days the elkbegan moving up Spread Creek on May 25,traveling southward into the Gros Ventredrainage (fig. 8) to Slate Creek where agroup of about 300 elk annually calve andrange for the summer months (ref. 8). Thecircuitous route taken by the elk to reach itssummer range, covering about 65 km, ratherthan traveling directly up the Gros VentreRiver valley for a distance of about 20 km,was unanticipated. The route taken also in-volved crossing a high divide that was stillsnowbound.

As the instrumented elk migrated, thenumber of elk with which she was associatedgradually diminished with distance and timeaway from the National Elk Refuge. On theRefuge she was a member of a scattered herdof 3000 to 4000 animals, and this numberdiminished to an average of 250 to 400 ani-mals.

108 A N I M A L O R I E N T A T I O N A N D N A V I G A T I O N

FIGURE 8. Gros Ventre River drainage to whichelk migrated from Refuge. Loop antenna, shownat top of the photograph, was used to communi-cate with ground-tracking system.

On May 15, two days before leaving theRefuge, the elk traveled with a group of 15animals. On May 23, and from time to timethereafter, she was observed alone or withonly one other cow. From this latter behaviorwe suspected the imminence of parturition.

From May 30 to June 10, sightings andradio fixes indicated that she moved only anaverage of 1.1 airline km per day with arange of 0.2 to 1.9 km. This was a consider-able reduction over her previous daily travel,and might have been related to calving. Aclose observation on June 8 established thatthe elk was in good condition, that most ofthe winter coat remained, and that no abra-sions or sores caused by the collar were evi-dent. It also appeared that the cow was notpregnant. A calf was not observed at this

time, but could have been hiding, since it is acommon practice of calves to hide when dan-ger is imminent (ref. 9). Possibly the de-crease in daily movement as indicated by ra-diotracking was a clue to time of calving.Such noticeable changes in daily movementas revealed by radiotracking, when properlyinterpreted and then verified by observation,can provide insights to animal activity andbehavior. For example, intermittent signalsfrom instrumented grizzly bears have beenvisually confirmed as an indication of dendigging (ref. 10).

An interesting result of the elk's summermovements is that she was more or less con-stantly traveling, spending only a few days toa few weeks in any one area or drainage. Theelk was last located by the ground-trackingradio on June 10. The next contact was asighting on July 28 in the Cottonwood drain-age about 20 km east of Slate Creek. Theprobable route of her travels (a gradualmovement) after leaving the SlateCreek-Mount Leidy area was eastward to theconfluence of Poison Creek with CottonwoodCreek. On November 14, she was acciden-tally shot by a hunter 8 km from this locationand just prior to her expected safe return tothe National Elk Refuge.

Daily movement of the elk on the Refugethat occurred before migration averaged 3.7km, based on 41 movements, and rangedfrom 0.6 to 14.6 airline km. Just prior to along trek on April 24, ground-trackingshowed that the elk had traveled an averageof about 2.6 airline km per day. On April 25,she backtracked 14.6 km toward the Refugefeeding lots (fig. 4). This was the longestsingle trek prior to migratory movement.Such movement back and forth in responseto weather and snow cover is typical duringApril. However, this return travel started be-fore a storm arrived and may have been inresponse to an approaching storm. The ba-

S E S S I O N I I : A N I M A L T R A C K I N G 109

rometer dropped, and snow fell for the nexttwo days.

Some animals apparently can sense an ap-proaching storm. A change in activity asso-ciated with an approaching snow storm wasclearly demonstrated while radiotracking aninstrumented grizzly bear to its winter den.This grizzly altered her previously recordeddaily activity pattern one morning andstarted moving rapidly toward her den inbright, sunny weather. Snow started to fall inlate afternoon, and the female grizzly arrivedat her pre-excavated den that evening (ref.10). Apparent early detection of weatherchanges by both bear and elk is intriguingand may be related to the animals' possibleability to detect infrasound waves created byapproaching but distant storms (ref. 11).Satellite as well as ground radiotrackingshould be a useful tool in probing this phe-nomenon in wild animals, perhaps evenunder controlled conditions.

Changes in the elk's activity and theirinterpretation, as well as the migratory ob-servations, indicate that behavior and migra-tion of individual elk can be studied in detailwith the aid of radiotracking and bioteleme-try ground-satellite systems. These studies canprovide information of value in the manage-ment of elk populations, as well as contributetoward a better understanding of the phe-nomena of animal behavior and migration.

RESULTS

The study was successful in demonstrat-ing the practicability of tracking .large free-roaming animals in natural environments bysatellite systems. The prototype IRLS instru-ment collar was somewhat bulkier and heavierthan required, and on the basis of informationderived from monitoring the instrument bysatellite, particularly the effect of the solarcells on battery charge, calculations indi-

cated a possible weight reduction of about 50percent down to about 5 kg. A fin antennais now available for the instrument, whichwould eliminate the large housing requiredfor the dipole antenna and reduce the profileof the instrument. Variable padding withfoam rubber to adapt the instrument to agiven elk would solve the problem of thecollar turning around on the elk's neck. Animprovement in the resolution of locationsto within. 1 km would be possible with thedevelopment of a low profile, omnidirec-tional, circularly polarized antenna. Experi-mentation with effective sensory systemsis needed to measure deep body temperature,skin .temperature, heart rate, and other phy-siological parameters. To eliminate externalwiring, implantable transmitters are requiredfor transmission of data to receivers in theinstrument collar. Miniaturized equipmentfor periodic data sampling and storage priorto transmission (every 12 hr) is needed.

The advantages of satellite systems aredescribed elsewhere (ref. 12). Briefly, satel-lites permit daily tracking and monitoring ona worldwide scale with instruments that areimmune to the effects of Earth's weather andprovide data under day or night conditions.Where animals are isolated in polar regions,the oceans, or deserts, satellites are especiallyuseful. To obtain adequate data on bird mi-grations over long distances and at high alti-tudes or marine animals covering great dis-tances, satellite systems are almost indispensa-ble. The uniqueness in satellite systems lies inthe ability to combine continuous trackingup to 6 months, or longer, with simultaneousmonitoring of physiological and environmen-tal parameters.

Despite the advantages of satellites, radiocontact with animals from the ground is alsoneeded for homing in on animals for directobservations. An integration of the two sys-tems is likely to be required in most research.

110 A N I M A L O R I E N T A T I O N A N D N A V I G A T I O N

An accurate system for tracking free-liv-ing animals and monitoring both physiologi-cal and environmental parameters will pro-vide a valuable new tool for investigating thebehavior and ecology of wild animals. Satel-lite systems can aid in investigating a vast ar-ray of important biological problems, includ-ing migratory movements and navigationalguidance mechanisms of animals, patterns ofdispersal and concentration associated withfeeding and reproduction, the entrainment ofphysiological cycles by environmental param-eters, and patterns of vector transmission ofdisease by migratory animals (ref. 12). Theknowledge gained through such studies willhelp provide the scientific basis for intelligentmanagement of the Earth's ecosystems.

ACKNO WLEDGMENT

We wish to thank biologists Harry V. ReynoldsIII and Vincent Yannone, and graduate studentSteven M. Gilbert of the University of Montana,for their assistance in this project. Joel R. Varney,Research Associate, Montana Cooperative WildlifeResearch Unit, University of Montana, contributedsignificantly to this project in testing and applyingthe electronic systems. James C. Maxwell, StaffEngineer, Ecology Program, Office of Environ-mental Sciences, Smithsonian Institution, aided inthe pretesting of the IRLS collar.

The IRLS instrument was conformed into thecollar for the elk by Radiation, Inc., Melbourne,Florida.

Tracking animals by satellite was stimulated bySidney R. Galler, Assistant Secretary (Science),Smithsonian Institution, who organized the 1966conference on this subject. We are grateful for hisencouragement .and inspiration. George J. Jacobs,Chief, Physical Biology, National Aeronautics andSpace Administration, was particularly helpful inthe development and administration of the project.

This project was supported by a NASA con-tract (NASW-1983) to the Smithsonian, Institu-tion. . . -

DISCUSSION

COCHRAN: You have called this a feasibilitystudy. Is it practical to conduct a study on the elk?

BUECHNER: Yes indeed, I think it is practical.We know the weight can be reduced at least onehalf, without doing any miniaturization. We alsoknow how to make a better configuration for thecollar and we have some ideas on how to improvethe antenna system. The costs can come down. Infact, potentially, if there are enough users, the costscould come down very quickly to something around$2000 or $3000 per instrument package.

We hope that next year we will be able to trackan elk during the spring migration and make peri-odic ground observations to correlate behavior withmigration movements and physiological parameters.

ENRIGHT: There may be a slight difference inthe elevation of the animal which could make a bigdifference in the apparent geographical location. Isthis a real problem?

COTE: The elevation is certainly a factor; wedo not assume that the Earth is a perfect sphere. Inthe case of the elk, changes were in the order of90m (300 ft) which did not greatly impact locationaccuracy. For high flying balloons or aircraft track-ing applications the altitude becomes a critical fac-tor and must be entered into mathematical equa-tions for location computation.

WILLIAMS: You state that your readings ex-tended over eight to ten minutes for one point.How is this possible?

COTE: Since the satellite is in view for 4 to 5min, multiple interrogations lasting 2 sec each areprogrammed. This allows up to five data samplesunder normal operational conditions where 1 min-ute intervals are maintained. The two frequenciesutilized in the IRLS system are 401.5 and 466.0MHz.

CARR: Did resolutions in your track-plots forthe elk correspond to those for the buoy? That is,do you get about the same fineness in separatingand locating points with the elk as you would intracking the buoy?

COTE: No. The buoy positions were more accu-rate since higher power equipment was used.Under these conditions the satellite need not be di-rectly overhead to obtain solid communication. Op-timum location accuracies with. the higher powerequipment are obtained at elevation angles between+5 and +50° with respect to the horizontal.

SLADEN: How did you measure skin tempera-ture?

COTE :. Readings of external skin temperaturewere obtained by a thermistor mounted on a ten-sion arm attached to the collar. The tension wascalibrated to enable skin contact under normal ac-tivity conditions.

S E S S I O N I I : A N I M A L T R A C K I N G 111

QUESTION: Do any of you object to using aharness?

CRAIOHEAD: Initially, we considered a harnessbut rejected it for a number of reasons. The elkreally has a very strong neck. We didn't have manyproblems with collars reversing in the initial tests.

• BULLOCK: There is a source of power that hasnot-yet been mentioned. This is the piezoelectricsource. Currently engineered devices obtain energyfrom the organism via its movements and produceabout %th or %th of a mW power continuouslywith very high efficiency. It would be a negligibleload for an ordinary bird in terms of extra work, todeflect a piezoelectric crystal to produce a milli-watt. The advantage is that you are getting awayfrom any prepackaged foreign power source andare dealing with an endogenous source of power.

The device, for instance, which Carl Enger(ref. 13) has been using in dogs takes some of thework from the respiratory muscles which bend asmall device, about 30 grams in weight, a cylinderabout 50 mm long and 10 mm in diameter. Themain element is a piece of ceramic which is de-formed very slightly. This deformation produces thepower—a relatively high voltage (around 20 V) atlow current. From this particular device they aregetting about 300 microwatts continuously.

What would be needed to increase the power toone milliwatt is another gram of weight increasingthe bulk from 30 to 31 grams. This would addenough ceramic material so that about a milliwattcould be obtained continuously. The problem be-comes where to attach the device. They are work-ing now loose in the pericardium, deformed by thebeating heart, and fixed to the vertebrae and ribs,deformed by respiratory movements. This puts theproblem back to the biologist where it really be-longs. There is essentially a negligible loading in re-spect to weight and to work.

The point is, that with this small a device youcould radiate milliwatts continually and interrogatethe animal every minute or every hour, instead ofcompromising with an interrogation once a week.

REFERENCES

1. ANON.: Some Prospects for Using Communi-cations Satellites in Wild Animal Research.AIBS, BIAC Spec. Kept. 51, 1966, 23 pp.

2. CRAIGHEAD, F. C., JR.; AND CRAIGHEAD, J. J.:Radiotelemetry of Large Western Mammals.Progr. Rept., 1965-66. AEG Contr. AT(45-l)-1929, 1966,67pp.

3. CRESSEY, J. R.; AND HOGAN, G. D.: The In-terrogation, Recording and Location SystemExperiment. Proc. Natl. Telem. Conf., sec.VI, 1965.

4. COTE, C. E.: The Interrogation, Recordingand Location System Experiment. NASAX-733-69-336, 1970, 22 pp.

5. COTE, C. E.: The Interrogation, Recordingand Location System Experiment. Geo-Science Electronic Symp. Trans., IEEE,Spec. Issue, 1970.

6. CRAIGHEAD, F. C., JR.; AND CRAIGHEAD, J. J.:1965. Tracking Grizzly Bears. BioScience,vol. 15, no. 2, 1965, pp. 88-92.

7. CRAIGHEAD, F. C., JR.; AND CRAIGHEAD J. J.:Yellowstone Field Research Expedition V.State University of New York at Albany,Publ.no. 31,ASRC, 1965.

8. ANDERSON, C.: The Elk of Jackson Hole. Wy-oming Game and Fish Comm., Cheyenne,Wyoming, 1958, 184 pp.

9. MURIE, O. J.: The Elk of North America.Stackpole Co., Harrisburg, Pa., 1951, 376pp.

10. CRAIGHEAD, F. C., JR.; AND CRAIGHEAD, J. J.:Grizzly Bear Prehibernation and DenningActivities as Determined by Radiotracking.Progr. Rept., 1968, Environmental ResearchInst, Montana Coop. Wildlife Res. Unit,1968, 49 pp.

11. GREEN, J. A.; AND DUNN, F.: 1968. Correla-tion of Naturally Occurring Infrasonics andSelected Human Behavior. Acoustical Soc.of Am., vol. 44, no. 5, 1968.

12. BUECHNER, H. K.; CRAIGHEAD, F. C., JR.;CRAIGHEAD, J. J.; AND COTE, C. E.: Satel-lites for Research on Free-living Animals.Bioscience, Dec. 15, 1971.

13. ENGER, C.: Proc. Artif. Heart Conf., NIH,Bethesda, Md., June 1969; Nature, vol. 218,no. 5137, Apr. 13, 1968, pp. 180-181.

BIBLIOGRAPHY

MACKAY, S. R.: Bio-Medical telemetry. Second Ed.John Wiley and Sons, Inc., New York, 1970.533 pp.

SLATER, L. E., ed.: Bio-telemetry. Macmillan Co.,New York, 1963, 372 pp.

SLATER, L. E., ed.: A Special Report on Bioteleme-try. Bioscience, vol. 15, no. 2, Feb. 1965, pp.81-157.

Reprinted from BioScience

Satellites for Research on Free-Roaming Animals

Helmut K. Buechner, Frank C. Craighead, Jr.,

John J. Craighead, and Charles E. Cote

Satellites for Research on Free-Roaming Animals

Helmut K. Buechner, Frank C. Craighead, Jr.,

John J. Craighead, and Charles E. Cote

Introduction

Earth-oriented satellite technologyprovides new opportunities to delvemore effectively and more deeply thanpreviously possible into some aspects ofthe behavior, physiology, and ecologyof free-roaming animals in their naturalecosystems, especially in remote areas.These opportunities come at a timewhen an urgent need exists for accurateinformation about the migratory pat-terns of endangered species of whales;the movements and habits of polar bearsthroughout the Arctic; migrations ofcaribou in regions of projected oilpipelines; the migratory behavior andisland-finding system in commerciallyimportant species of large sea turtles;the relationships of African elephantsand plains game to changes in vegetationinduced by subsistence cultivation, newfire regimes, and overgrazing by domes-tic livestock; and similar problems af-fecting the future of the total worldecosystem. Investigations along theselines are now feasible; and with minia-turization and new systems concepts forreducing power requirements, ultralight-weight instrument packages for trackingmigrating birds, even small ones, bysatellite may soon become a reality. Thecapabilities of existing satellite systemsand some applications in biologicalresearch are considered in the presentpaper.

The authors are, in order: Senior Ecologist,Office of Environmental Sciences, Smith-sonian Institution, Washington, D.C.; AdjunctProfessor of Biology, Department of Biology,State University of New York at Albany, NewYork, and President, Environmental ResearchInstitute, Moose, Wyoming; Leader, MontanaCooperative Wildlife Research Unit, U.S.Bureau of Sport Fisheries and Wildlife,University of Montana, Missoula, Montana;Space Technologist, Goddard Space FlightCenter, Greenbelt, Maryland.

T5

T4

^T3METEOROLOGICAL

BALLOON

T2

GROUNDAQUISITION

AND COMMANDSTATION

Fig. 1. The Interrogation Recording Location System (IRLS) on the Nimbus meteorologicalsatellites provides a regimented two-way radiotracking and monitoring system. Althoughdesigned originally for meteorological balloons, it was possible to conform one electronicplatform as a prototype instrument collar for tracking an elk. Addresses of electronic platformsand anticipated times of platform overpass are programmed into the satellite on anorbit-by-orbit basis from the command station. As time elapses into the orbit, interrogations ofplatforms are executed at the programmed times. During each interrogation the short-rangedistance from the satellite to the platform is measured by the satellite. A minimum of twointerrogations is required per platform to determine its position.

Satellite Tracking andData-Collection Systems

Systems for satellite tracking anddata collection have been under devel-opment in the National Aeronautics andSpace Administration and the CentreNational d'Etudes Spatiales (France)since the late 1960s. These systems weredeveloped primarily for application tometeorological studies of atmosphericconditions on a global scale (Cote,

1971; Laughlin, 1966). Additional uses,such as animal tracking and monitoringoceanographic buoys, have been foundin other scientific disciplines (Figs. 1,2).

A representative systems concept isshown in Figure 3. The essential ele-ments consist of a satellite, remotelydeployed sensor monitoring platforms(transponders, repeaters, or transmit-ters) and a central ground-data-processing facility. Sensor data from'remote platforms are collected by satel-

December 15, 1971 1201

TABLE 1. Satellite-tracking and data-collection systems

System

Omega PositionLocationEquipment(OPLE)

InterrogationRecordingand LocationSystem(IRLS)

IRLS

EOLE (France)3

Random AccessMeasurementSystem(RAMS)

SatelliteDate of LaunchType of Orbit

ATS1968Synchronous

Nimbus 31969Polar

Nimbus 41970Polar

EOLE1971Near Polar

Nimbus F1974Polar

System Capacity Platform Data ChannelsPlatorfms Weight per Platformper Orbit (kg) ±1% Resolution

40 16 8

10 11 8- 132(optional)

185 4.5 8-630(optional)

511 3.2 8

1000 0.45 3

LocationAccuracy

(km)

±2 (day)

±4 (night)

±1.5

±1.5

±1.5

±1.5

Derivative of Aeolus, Greek god of the winds.

lite and relayed to the ground station.Simultaneously with data collection, thegeographical coordinates of the plat-form location are determined throughranging, doppler, or relay of low-frequency navigation tones (omega).Processed data are sent to users on adaily basis.

Various orbital configurations can beused to achieve desired areas of cover-age. A system of geostationary equatori-al (synchronous) satellites can collectand relay information continuously(real-time) from platforms over most ofthe earth's surface. A single geostation-ary satellite over the equator can inter-rogate sensor platforms located within±70° longitude of the subsatellite point.Thus a system of three geostationarysatellites can be programmed to provideservices on a global basis.

To achieve coverage on polar regionsbeyond 70° latitude, low orbiting ornear-polar orbits are employed. A polarorbit (e.g., Nimbus satellite) at a heightof 1100 km provides complete earthcoverage every 24 hours. Platforms canbe interrogated every 107 minutes inpolar regions and every 12 hours at theequator. Lower orbits provide less polarcoverage, but reduce intervals betweenpasses at the lower latitudes. •

To date, two concepts have beendemonstrated through actual operation;two additional systems are scheduled

for 1971 and 1974. These systems aresummarized in Table 1. In this tabula-"tion, the weight of platforms shows adownward trend with time. Of par-ticular interest is the Nimbus F RandomAccess Measurement System (RAMS)which offers capabilities in 1974 com-mensurate with a great majority ofanimal tracking requirements. Futuresystems under study at NASA willattempt to approach the RAMS weightcategory for use with synchronous satel-lites, thus providing continuous, real-time coverage. Continued research inlow orbiting systems is under way witha view toward reducing size and weightparameters to levels compatible withtracking requirements for birds andother small animals.

Applications of SatelliteSystems to Animal Tracking

The International Conference on theBiology of the Whale held in Washing-ton, D.C., in June 1971, focused newattention on the serious problem ofendangered species of whales. The entirewhaling industry may collapse within afew years, and some species, such as theblue whale which is down to about 600individuals, may never recover (Fisher et

WORLDWIDE SATELLITE TRACKING COMBINED WITHLOCAL GROUND MONITORING OPENS NEW HORIZONSIN ECOLOGICAL RESEARCH.

Fig. 2. In polar otbit a satellite covers all points on the earth in a single day with the capabilityof interrogating a variety of animals. Ground radiotracking systems will continue to be valuableas a method for homing in on an animal for direct observations.

1202 BioScience Vol 21 No. 24

MULTI-SENSOR DATA COLLECTION PLATFORM NO. i

USER

Sen**No. I

•••

SrmoiNo. N

- 1

1 '

t

f1

1

LATFORM ELECTRONICS

~ -#Analog toD.»tat

Convener

-

A.«nn.

\ /

T,._,

OaPIS>CeL

y

ORBITING SATELLITE

MULTI SENSOR DATA COLLECTION PLATFORM NO. M

Fig. 3. Generalized satellite data-collection system.

al., 1969). Lack of scientific informa-tion on the ecology and behavior ofwhales is a severe handicap in develop-ing sound management programs forthese animals. Baldwin (1966) has sug-gested a system for tracking andmonitoring whales by satellite using aself-propelled float, locked onto thewhale by an acoustic tag, which willfollow the whale, collect data fromelectronic packages when the animalsurfaces, and relay the data to thesatellite. Another possibility is theperiodic release of instrument packagesfrom the whale to the ocean's surfacefor relay of data to the satellite (RobertM. Goodman, personal communica-tion).1 Satellite systems not onlyprovide an essential method for researchon wide-ranging marine mammals butprobably also the most economicalmeans for acquiring data, even frommodest numbers of 10 to 100 in-dividuals.

The phenomenon of island-findingrepresents one of the most advancedcases of animal navigation and, since themarine environment presents the fewestdistracting variables, allows optimuminterpretation of results. Carr (1962,1965, 1966) has proposed the use ofsatellite radiotelemetry in tracking thegreen sea turtle. Knowledge of the travelpattern is needed to identify the self-guiding mechanisms of this animal. Al-though aquatic, the green sea turtlesurfaces at short intervals to breathe. Itslong-range cruising is done mostly atdepths no greater than 3 to 5 m; andsince the travel takes place across water

tion. 1971.Goodman, Robert M. Personal communica-

thousands of meters deep, there is nofeeding and thus no sounding. As theturtles come ashore to nest at AscensionIsland, having just completed the migra-tion from the South American mainlandor Lesser Antilles, they can be movedback to the feeding grounds and trackedby satellite during their return toAscension Island, over distances of 2000to 5000 km. Results of previous ob-servations indicate that, when the tur-tles are removed from their nesting site,they remain strongly motivated to thenesting site. Understanding the naviga-tional system in sea turtles is of morethan academic importance. Sea turtlesare commercially valuable and some ofthem, such as the Atlantic hawksbill,leatherback, and Atlantic Ridley, areendangered species.

Global concern for the conservationof polar bears has been reflected inthree international conferences on thestatus and biology of this animal duringthe past 6 years. Knowledge about themovements and denning habits of thepolar bear is inadequate as a basis formanagement. Since it lives on ice thatmoves and changes its appearance, thepolar bear must require unusualmechanisms for maintaining orientation.The circumpolar relationships of sub-populations to one another are im-portant, particularly in view of thepossibility that hunting of polar bearscould be decreasing the totaj popula-tion. Scientists in Russia, the UnitedStates, Canada, Denmark, and Norwayalready have a framework for coopera-tion in research on polar bears, and anintegrated effort with a satellite systemcould be stimulating and profitable.

Caribou have declined in numbersduring recent years; the reasons for thisare not clear. Local human populations

in Canada and Alaska still depend'uponcaribou as a source of food. The lowproduction of lichen vegetation on thearctic tundra could not support largeherds of caribou were it not for theanimal's wide-ranging movements. Themonitoring of herd movements by satel-lite, in combination with remote sens-ing, could shed new light on nomadicmovements in relationship to thecondition of the vegetation. The pos-sible influence of oil pipelines on themovements of caribou and the effects ofcaribou on the pipelines are uncertain.Satellite studies of the caribou's move-ments may help to clarify these poten-tial interrelationships.

In recent years elephants have be-come agents in dramatic changes invegetation in East Africa, convertingwoodland and wooded grassland toopen grassland (Buechner and Dawkins,1961; Laws, 1970). In the TsavoNational Park and vicinity in Kenya,where about 40,000 elephants now existon 44,200 km2 (17,000 square miles) ofhab i t a t , dense Commiphora-Acaciavegetation has been converted into opengrassland as the population of elephantsbecome increasingly confined to thePark. The restriction of range, by cut-ting off migratory routes and intensify-ing human activities (cultivation, char-coal burning, settlements) outside thePark boundaries, has prevented popula-tion dispersal from functioning as anatural regulatory adjustment to in-creasing densities in elephants nearlyeverywhere in Africa. The changes invegetation are in the long run unfavor-able to the elephants, whose optimumdiet probably includes no more than50% grass. Precise knowledge of thed i s t r i bu t ion and movements ofelephants over a period of several years,in combination with remote sensing ofthe condition and trends in the vegeta-tion, is needed as a basis for soundmanagement practices to preserveelephants in East Africa.

The mechanisms of avian orientationand navigation have fascinated scientistsfor many years, and recent knowledgewas explored at an AIBS conference inSeptember 1970 (Caller et al., 1971).2

Apparently birds have orientation sys-tems that provide information about

2Galler, S. R., G. J. Jacobs, K. Schmidt-Koenig, and R. E. Belleville (eds.). 1971.Animal orientation and navigation: A sym-posium, 9-13 September 1970, Wallops Sta-tion, Virginia. 16 p.

December 15, 1971 1203

their actual position in relationship totheir destination, as well as guidancemechanisms for finding pinpoint loca-tions on the earth. These systems seemto function for some birds in the ab-sence of celestial cues, under overcastcondit ions. Possibly the animal'sguidance mechanism senses the Coriolisforce (Yeagley, 1947) or the earth'smagnetic field. Satellite tracking andmonitoring of physiological and en-vironmental data during the premigra-tory period, during migration, and afterarrival at the destination would provideexcellent opportunities for advancingresearch on avian navigation and theunderlying physiological basis for migra-tion. The monitoring of parameters onsmall migrating birds is a demandingchallenge for electronics engineers, onethat will require considerable technolog-ical development in terms of sensors,microminiaturization of electronics, andnew concepts in -satellite systems toreduce power requirements.

The economic, aesthetic, and recrea-tional importance of migratory birds isrecognized in three international con-ventions of 1916, 1937, and 1942, withresponsibility invested in the federalgovernment under the Migratory BirdTreaty Act. Until now, knowledge ofmigratory patterns has been based al-most entirely on studies of bandedbirds. Opportunities for obtaining moreprecise information on migratory move-ments, for locating unknown breedinggrounds, and for investigating the trans-mission of diseases by using satellitesystems are intriguing.

The wandering albatross appears tomove around the world between 40°and 60° S latitude. The pattern of dailyand seasonal movements is imperfectlyknown from observations of bandedbirds, and it is not known how far thebird moves in gathering food for nest-lings. It would be valuable to discoverthe albatross' mechanism for navigationover the open sea. These birds could beeasily captured in New Zealand and onSouth Georgia Island during the nestingseason.

Knowledge of migratory patterns andmechanisms of navigation have a sig-nificant bearing on air-traffic control toavoid bird strikes. The crash of a Vis-count airliner near Baltimore in 1962might have been avoided had the migra-tory behavior of whistling swans beenpredicted. The problem of laysan al-batrosses and military aircraft at Mid-way is a classic example of avian inter-

ference at island airports. Aside fromimperiling human life, bird strikes causeconsiderable economic loss annuallythrough damage to aircraft.

Satellite tracking could be used tolocate the breeding grounds (completelyunknown) of the Tule goose, an en-dangered species that winters in Califor-nia, and those (only partially known) ofthe arctic peregrine, an endangeredspecies that migrates along the easterncoast of the United States. The summerrange of nonbreeding subadult whoop-ing cranes and the winter range ofAleutian Canada geese are also un-known. The migratory patterns of thewestern bald eagle are inadequatelyknown. In all these cases, satellite track-ing of a few individuals can yield in-formation of value in the preservationof the species.

Migratory birds are important hostsof arthropod-borne viruses, such as en-cephalitis and hemorrhagic fevers, thatcan also infect man, domestic animals,and wild vertebrates other thanmigratory birds. These viruses are car-ried in the blood of migrating birds aswell as in mites and ticks being trans-located by the birds. Intensive studies ofEuropean birds (Watson, 1971; Watsonet al., 1971) have shown that about 10%of a given species is infected. The ideaof finding out where an infected birdgoes is extremely important, especiallyfor viruses that occur in widely separat-ed geographical areas. Crimean hemor-rhagic fever, for example, infects peopleworking with cattle in the Crimea and inthe Republic of Congo. About 20% ofthe infected persons die of the disease.Knowledge of what happens to theinfected bird en route, and at its desti-nation on the winter range, could con-tribute significantly to understandingthe epidemiology of the disease or-ganism. The blood of birds capturedwith mist nets along the migratory routecould be monitored for the virus, afterwhich the birds could be released withtransmitters and tracked by satellite.

The relationship between fungal rustsand other plant diseases and avian car-riers could be thoroughly investigatedwith space technology, using multi-spectral remote sensing and animaltracking to correlate avian activities andcrop infections.

Research on some of the problemsdescribed above could be implementedas early as 1974, using the doppler-shiftlocating and monitoring system (3 datachannels) on Nimbus F. The instrument

packages on the animal would weighfrom 0.5 to 1 kg, thus limiting most,studies to the larger mammals. Systemsfor future satellites have already beendesigned in which the instrumentpackages would weigh as little as 50 g,providing a tracking capability over aperiod of 3 to 4 months (withoutchannels for monitoring physiologicaldata). However, many of the importantand intriguing biological problems in-volving small migratory birds willdepend on the development of newsystems concepts for reducing theinstrument's weight below 50 g.

Further ideas on applications andequipment needs are provided in asurvey of satellite user requirements(Pascucci et al., 1971).3

Satellite Tracking of Animals

Satellite systems for tracking andmonitoring animals open new horizonsby increasing the access to data byseveral orders of magnitude, as groundradiotracking and biotelemetry havedone previously. Complete coverage ofthe earth is attainable in a single day, orless, depending upon the choice oforbital parameters. The satellite systemis impervious to the earth's weather,thus offering the researcher an instru-ment equally useful in polar, temperate,or tropical zones of the world, andunder day or night conditions. Otheradvantages of satellites include:

1) Satellite-derived position informa-tion specifies location unambiguously interms of longitude and ^latitude, asopposed to ground radiotracking whereinformation consists of an azimuth andan ambiguous range distance, or a fixobtained from two or more bearings.

2) Animals can be tracked readilywhere isolation is a factor, as in polarregions, in the open ocean, or in deserts.

3) Satellites can track migratinganimals impossible to follow adequatelyby radiotracking from the ground oraircraft, including animals confined toinaccessible areas, birds making lengthymigrations at high altitudes, or marineanimals covering great distances (usingsurface contact).

4) Satellites are highly suitable forautomatic and regular recording of data

3Pascucci, R., N. Liskov, and L. Garvin. 1971.Phase I Report, Wildlife Research Program,R a y t h e o n Co., Autometric Operation,Alexandria, Virginia. SO p.

1204 BioScience Vol. 21 No. 24

on wide-ranging animals over a long" p'eriod of time (a year or more).

5) Data can be gathered by satellitesalmost simultaneously from a numberof widely separated instrumentedanimals of the same species.

6) Synchronous, geostationary satel-lites can monitor numerous animals andtheir environments on a real-time basisover extensive areas of desert, tundra,grassland, or a large river system.

Despite the advantages of satellitesfor tracking and monitoring wild ani-mals, radio contact with animals fromthe ground will continue to be requiredin biological research. Satellite systemswill supplement, not replace, ground-tracking systems. Ground trackingprovides an excellent way to contactindividual animals whenever this may benecessary for observing the animal'shealth or for pretesting equipment priorto satellite tracking. Radiotracking fromthe ground is also an effective way forhoming in on an animal for direct visualobservations on locations, and for ob-serving behavior and daily activity tocorrelate with physiological and en-vironmental data monitored simul-taneously, whether by satellite orground systems. Both systems are valu-able in ecological and physiological re-search on animals in natural environ-ments. Each has unique attributes, andan integration of the two systems islikely to be required in most research, atleast until satellite systems are perfect-ed.

Need for Animal Tracking Facility

The complexity and expense indeveloping satellite systems for trackingand monitoring free-roaming animals aresuch that coordination of the efforts ofbiologists and engineers, combined withan integration of programs in variousgovernment and private agencies, is re-quired through some institution, aspointed out in a recent report by theSpace Science Board of the NationalAcademy of Sciences (Townes, 1970).The Smithsonian Institution undertookthis responsibility for the elk experi-ment (Craighead et al., 1971). Ultimate-ly, an international facility will be re-quired, with a design that will encourageindividual scientists and engineers todevelop their own research interests andmaintain creative working relationships.

Some of the requirements for aninternational facility for animal tracking

and monitoring by satellite are present-ed in Townes' recent review. Theyinclude the need for fixed and mobilemonitoring stations to receive data fromsatellites, airplanes, and balloons; asystem to bring biologists into contactwith technical consultants; laboratoryfacilities for developing prototypeinstruments; and computer capabilitiesfor acquisition, processing, storage, andretrieval of data.

The development of animal trackingby satellites as a useful and economicaltechnology depends as much upon awell-functioning facility as it does uponadequate financial support. An integrat-ed effort among biologists and engineersworking with real problems in the field,with all of the attendant difficulties ofhandling living organisms and con-trolling biological variables, is essentialto the successful advancement of thetechnology. With a concerted effort, itis conceivable that within a decadesatellites dedicated to ecological re-search could be available to the scien-tific community. In addition to basicresearch, the same satellite systemscould be used for tracking marine fish,whales, sea turtles, migratory waterfowl,and other animals to provide a morescientific basis for harvesting and con-serving these resources, and for improv-ing the control of disease transmitted bymigratory animals. These advantages ofsatellite systems for advancing our un-derstanding of the functioning of eco-systems provide compelling reasons fora major effort to develop a worldwidecapability of satellite tracking andmonitoring of animals in natural en-vironments.

Acknowledgments

We wish to thank George J. Jacobs,Chief, Earth Ecology Program, NationalAeronautics and Space Administration,for the stimulating discussions that ledto the present commentary. For someof the ideas concerning satellite trackingof birds we are grateful to George E.Watson, Chairman, Department of Ver-tebrate Zoology, Smithsonian Institu-tion; Robert E. Shope, Yale ArbovirusResearch Unit, Yale University; andJohn W. Aldrich, Research Staff Spe-cialist, Division of Wildlife Research,Bureau of Sport Fisheries and Wildlife.For reviewing the manuscript criticallyand offering many helpful suggestionswe owe thanks to Sidney R. Galler,

Deputy Assistant Secretary for Environ-mental Affairs, Department of Com-merce, who encouraged satellite track-ing of animals while Assistant Secretaryfor Science at the Smithsonian Institu-tion; Robert Galambos, University ofCalifornia, San Diego; and George J.Jacobs. We appreciate the ideas andcomments we have received, but weacknowledge full responsibility for thefinal statements in this paper.

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