TELEMETRY STUDIES OF THE INTERNAL BODY TEMPERATURES OF ADIgLIE AND EMPEROR PENGUINS AT CAPE CROZIER, ROSS ISLAND, ANTARCTICA Jo•N C. BoYr) A•r) W•t,t,•A•4 J. L. SLADEN HO•rEOT•ER•4Sof both tropical and polar regionsare able to regulate internal temperaturesonly within certain environmentallimits. Extension of theselimits is possibleonly by physiologicaland/or behavioraladapta- tions that are often more conspicuousin speciesof very cold environ- ments. Cape Crozier (Ross Island, Antarctica) is the extreme southern locality where comparativefield studiesof the Addlie (Pygoscelisadeliae) and Emperor (Aptenodytesforsteri) Penguinsare possible.With emphasis on investigationof behavioral adaptationsin temperatureregulation, the internal body temperaturewas monitoredand its variation studied during two australsummers of field studies,1965-66 (Sladenet al., 1966) and 1966-67 (Boyd et al., 1967). Previous investigators(Eklund, 1942; Goldsmith and Sladen, 1961; Prdvost, 1961; Prdvost and Sapin-Jaloustre,1964; Mougin, 1966) had determined internal temperature values for these species,but our data present values of abdominal cavity temperaturesmonitored continuously during selectedstates of behavior. The study was aimed at further de- velopmentof a biotelemetrysystem to monitor the physiologyand be- havior of unrestrainedbirds. In particular, such a technique might be employed to study the winter-nesting Emperor Penguins in 24-hour darkness and severe weather conditions, as they move around while incubatingor broodingon the sea ice of the rookery. Field investigationswere carried out at the Addlie Penguin rookery (77 ø 26' S, 169ø 18' E), 8 km northwestof Cape Crozier and 7 km west of the Emperor rookery. About 150,000 breeding pairs of Addlie Penguinsare presentin the main rookeryin contrastto the 1,000 to 2,000 pairs of Emperorson the nearby sea ice. The Addlie rookery is part of the large ice-free area at the easterntip of RossIsland and benefits from a northernexposure and frequentwinds, keepingsnow cover at a mini- mum. Nearby Mount Terror (altitude 3,230 m) and the loweredalbedo of the dark exposedground (in contrastto that of nearby ice fields and the Ross Ice Shelf) considerablyaffect the climate of the rookery. Our 1966 67 weatherobservations (Figure 1) were taken from the Jamesway hut (134 m elevation). Janetschek(1967: 215) givesa summaryof the metereologicalconditions of RossIsland. Most field work was done at a coastal site (27 m elevation) from a hut 366 The Auk, 88: 366-380. April 1971 April 1971] Penguin Temperatures 367 m OCT.I NOVEMBER I DECEMBER I dANUARY IFEB- MAXIMUMeee©ee ,• ANDDIRECTION ß ß • WINDSPEED • -20- ---20•BELOWOVER IO 5M• M• Figure 1. Weather observations at Wilson House (Jamesway), elevation 134 m, Cape Crozier, from 28 October 1966 to 7 February 1967. surroundedby penguin colonies(Figure 2). Local screeningby low hills to the west and by Mount Terror exposedbirds to daily periodsof shade, varying from 7 hours 20 minutes (9 November) to 34 minutes (23 December). Air temperaturesand wind speedswere taken 40 cm above groundand at this site temperatureswere 1ø to 2øC warmer than at the Jameswayand the prevailingwind was southeasterly.Most experimental birds were kept in aluminum pens of 8 cm mesh--the Addlieson their nest sitesand the Emperorson a snowfield (after being flown over from their rookery by helicopter). Adults and the larger immature birds were flipper-banded (Sladen et al., 1968: 214). Nestling Addlie penguins were marked with plastic bands or tape. The terrestrial ecology of the Addlie and Emperor Penguinsis re- viewed by Pr•vost and Sapin-Jaloustre(1965) and Stonehouse(1967) has summarizedwhat little is known of their marineecology. The ecology, behavior, and physiologyof the Ad•lie Penguin are treated by Sladen (1953, 1958), Sapin-Jaloustre(1960), Taylor (1962), and in five articles in the recent monographon Antarctic avian studies (Austin, 1968). Physiologyand breedingbehavior of the emperorare coveredby Pr•vost ( 1961) and breedingbehavior by Stonehouse(1953). METltODS Conventio,nalmeans of measuringinternal body temperaturesmay reducethe useful- ness of the measurementsbecause of the animal's reactions to repeated human disturbance. Recent electronic developmentshave made the use of implanted telemeterspractical for field experiments.Telemetry was first used for field studiesof animals in the Antarctic in 1957 to determine egg temperaturesof incubating Ad•lie 368 BoYt• ^•u S•^•r• [Auk, Vol. 88 ROSS SEA \ •,APE CROZIER SEEINSERT x LOWœ,,uT• -- o [] ADœL,EADEL,E,00KERY • --'•n,•.ER,0V.•966 ß EMPERORROOKERY I --• SCALE ROSS s•u•Y ARœA ISLAND \ v/ ROSS _ E•-••,u••••• SHELF SCALE(M)• •.•.0 CA,E •, • •0 • CRO*ER Figure 2. CapeCrozier, Ross Island, and the study area. Penguinsand SouthPolar Skuas(Eklund and CharItOh,1959). In 1965preliminary work was done at Cape Crozier (Sladenet al., 1966) with telemetersimplanted in both adult and chickAddlie Penguins, part of a systemdeveloped by KennethBindle (University of Saskatchewan,Saskatoon, Canada). The presenttelemetry system, designed and constructedunder the supervisionof HowardA. Baldwin(Sensory Systems Laboratory, Tucson, Arizona), was based upon implantableunits measuring 3.7 X 1.5 X 1.8 cm and weighing20 g. The transmitter had a pulsed signal (27 millicycles/see),the rate of which was the inverse function of body temperature.Each telemeterwas poweredby two 1.5-v batteriesin series (both silveroxide and mercurycells were used), with a practicallife of 2-3 weeks, and the unit was encasedin epoxy and urethane,with additionalprotection given the batteriesby Silasticcoating. Use of a crude receivingantenna was necessary after damagein highwinds, and the rangeof the signalfrom an implantedtelemeter in the abdominal cavity of a free-living bird was 9-12 m. A 14-channelreceiver was April 1971] PenguinTemperatures 369 connectedto a digitalcounter that registeredthe signalpulse interval in milliseconds on a chart recorder. The receiver and the cou.nter-recorder were housed in two field cases,each 37 X 15 X 15 cm and weighing7.2 kg, and poweredby nickel- cadmium rechargeablebatteries. Calibration curves were made between 35 ø and 41øC and observed temperature valueswere calculatedfrom the fitted regressionline of the individualtelemeter. A changein resistancecharacteristics with time ("drifting") was notedin eachtelem- eter, but this error could be controlledby choiceof data soo.nafter calibration. Maximumerror in temperaturedetermination occurred during field calibration,and total calculatederror rangedbetween ñ 0.13ø and ñ 0.24øC,depending upon the individualunit. Estimatesof the 95 percentileconfidence interval were made for (1) the wholecalibration li.ne of the individualunit for a giventime period(the intervalsranging between ñ0.6 ø and ñ 1.1øCdepending upon the unit), and for (2) the mean "resting"abdominal temperature value of eachbird (the intervals rangingbetween ñ 0.1ø and _ñ0.2øC). The telemetertime constant,or responsetime, was 90 seconds--thetime requiredby the telemetersto completeapproximately two- thirdsof a totalchange of 10øC(20 ø to 39øC)when shifted between two waterbaths. In the abdominalcavity it was assumedthat the implantedtelemeter and the encapsulatingcyst formedaround it were affectedby changesin temperaturesof the surroundingtissue much as a corresp.o.ndingtissue mass in a similarsituation (Mackay, 1968: 253). The similarityof sucha massto water cannotbe assumed and the responsetime obtainedin the waterbath is reportedonly as a demonstrable characteristicof the system. Thermistorprobes (Yellow SpringsInstrument Co.).--(1) Abdominali.nsertion (Model421): internalbody temperatures of nestlingAd61ie chicks were monitored by a probeinserted 3 cm abdominally,just posteriorto the proventriculus,and sutured externallyto the skin. (2) Proventricularinsertion (Model 401): internal body temperaturesof severalbirds were mo.nitoredby an insertionof 30 cm (Ad61ie adults)and 35-40 cm (Emperoradults). Averagevalues were within 0.4øCof mean "resting"values obtained from telemeters.Control measurements were made with this probeduring telemeter calibration. (3) Surfacetemperatures (Model 421): probes wereattached by tape (5 mm wide) to the palmarsurface of the flipperand to the acrotarsal surface of the foot. Rectal thermometers.--Internalbody temperaturesof severalbirds were monitored by an insertionof 7-8 cm throughthe cloacainto the rectum. Rectal temperatures were recordedwithin a minute from experimentalbirds capturedfor periodicweigh- ing--values were taken after at least 30 secondsof insertion,but within 1 minute of capture. In eight instanceswhen simultaneousreadings were taken, all rectal temperatureswere within ñ 0.3øC of the telemeterrecord. Observationswere read from telethermometers(Yellow SpringsInstrument Co., Models41TD, 43TF and 43TK) and recordedcontinuously on a battery-poweredpotentiometer recorder (Instrument Corp. of America, Model 400). Thermal stability and easeof telemeterimplantation were major reasonsfor the choiceof the abdominalcavity. Complexvariation in thermalcharacteristics over the whole body force any representativeinternal body temperatureto be a statistical abstraction. It was assumedthat temperature measurementin a deep central area will approximatea meaningfulestimate of internal body temperaturemost closely becausethese areas require a minimumof temperaturevariation in order to function correctly. The abdominalarea probably approachesmore closelya steady state conditionof temperature.During the 1965-66season