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SON{EFIELD TECHNIQTJESFOR ECOLOGICAL RESEARCHON EMPEROR

APTENODYTESFORSTERI

GRAHAM G. ROBERTSON

AustralianAntaraic Division, ChannelHighway, Kingston, Tasmania 7050, Austalia

Received10 May 1991,accepted 15 July 1991

SUMMARY

ROBERTSON, G. G. 1991. Some field techniquesfor ecological researchon Emperor PenguinsAptenodytes forsteri. Marine Ornithology19: 9l-101.

This paper describes the following techniques for conducting ecological research on Emperor Penguins Aptenodytesforsteri: capture and restraint, measuring body masses,marking individuals for identification, collecting stomach contents, preventing liquid radio-isotopesfrom freezing in sub zero temperatures,handling adultsduring incubation and brooding, withdrawing blood samplesand attachingdive recorders. The techniques describedare of particular relevanceto field researchconducted during the Antarctic winter.

INTRODUCTION Penguins and may even limit the scope of the researchat the planning stage. The Emperor Aptenodytesforsteri is by far the largestand most powerful seabird. Adults stand The purpose of this paper is to describe methods as tall as ll5 cm and weigh up to 40kg at the adopted during a comprehensive study of the feeding beginningof the reproductivecycle (Prevostl96l). ecology of Emperor Penguins. The study sought The breeds through the Antarctic winter information about the ' diet composition (by under the most severe weather conditions stomachflushing), food and energy consumption(by experiencedby any , with ambient temperatures isotope turnover) and foraging parameters (by as low as -35oC and even -60oC when -chill is attachment of time-depth recorders and radio considered. Becauseof the severity of the Antarctic transmitters)during 1988 at the Auster (670 23'5, winter the Emperor Penguin is probably the most 64 02'E) and Taylor Glacier (670 28'S, 60 53'E) difficult species of penguin to study, for the coloniesnear Australia's (670 36'S, conditionsthey experiencemust also be facedby the 62 53'E). The methods described are intended to researcher. minimize stress experiencedby Emperor Penguins when handled, reducepersonnel requirements in the Many of the field techniques considered to be field and increasethe efficiency by which research standardin acological researchfor other speciesof questions can be answered. The difficult task of penguin involve an added degree of difficulty, counting Emperor Penguins. an important part of particularly for the inexperiencedresearcher, when ecological research on this species, will be applied to Emperor Penguinsduring winter. The consideredin a later paper. practical nuances of research methodologiesare rarely reported, yet they have an important beanng DESCRIPTIONOF TECHNIQUES on the outcome of field research on Emperor 92 ROBERTSON:EMPEROR PENGUINS Maine Omitholog 19

Catching and restraining Emperor Penguins and 18 cm and 50 cm in diameter at the narrow and wide ends, respectively. The bag for pre-incubation Totals of 572 adults and 443 chicks were caught for rnales and birds, which were fatter than various reasons during the study. To minimize adults feeding chicks, exceeded these measurements disturbance to the colony, whenever possible adults by 2 cm and 5 cm at the narrow and wide ends. were caught several hundred metres to seaward of respectively. Each bag was slightly oversized so if the colony as they travelled to or from the edge. necessary it could be folded over the restrained lndividual adults were caught by tackling them bird's head to cover its eyes, which tended to subdue rugby-style (taking care not to land on the bird) as it. The ends of the bag were reinforced by rope they tobogganedon the sea-ice. Most penguins were sewn into the canvas and metal eyelets were placed caught after pursuits of less than 25 m; longer chases around the wide end as attachment points for were abandoned for fear of unduly stressing the weighing scales. Chicks up to about I kg (c. Z birds. An alternative and perhaps less stressful weeks of age) were handled in a calico bag; those method of capture would be to immobiliz.e the between I kg and 3 kg were restrained in bags as for penguin in the standing position with a shepherd's adults, but 50 cm in length and 12 cm and 30 cm in crook attachedto a 2-m long handle (G.L. Kooyman diameter at the narrow and wide ends, respectively. pers. comm.). Once stationary the penguin can be approached by the researcher and physically Weighing Emperor Penguins restrained. Emperor Penguins can be weighed by suspending When many adults were required they were caught them from a scale by hand, from a scale under a by herding them into an enclosure made from tripod (Klages 1988), or by standing them on a sections of a portable sheep yard (McShane, platform balance (Le Maho et al. 1916). Becauseof Australia) which is self supporting when erected, their height and massEmperor Penguinsare difficult light in mass, easily built and collapsible. These to suspend and the procedure usually requires more featuresmeant that an enclosure of almost any shape than one person. The one-person weighing system (including circular, which allowed the birds to move (Fig. l) consists of a 1.5 m long metal bar placed unimpededby corners) or size could be quickly and over the operator's shoulder and joined by a rope to easily built. The yard consisted of numerous a foot plate anchored to the sea-ice by the mass of detachablepanels, each of two hinged 1.9 x 1.0 m the operator. The penguin is slung from weighing sectionsweighing 23 kg. Since Emperor Penguins scalespositioned in front of the operator as shown in are inclined to follow one another when moving on the figure. The technique was particularly useful the sea-ice two or three people could shepherd when the body massesof large numbers of penguins groups of 20 or so birds into the yard at a time. were required (e.g. massof arrival or departure). Creche-stagechicks were caught by assembling sections of the sheep yard around them as they To reduce strqss on the birds during handling it is huddled on the sea-ice. Single chicks were caught important to restrain Emperor Penguins in posfures with a long handled(3 m) butterfly net. that are natural to them, either upright on their feet l( or prone on their ventral surface. Penguins I Following their capture, the penguins were restrained on their backs struggled more vigorously )l restrained for experimental purposes in a heavy duty than those held in the postures above, and this could ,t cone-shaped canvas bag (Fig. l). Adults less than be expected to have increased the trauma rf c. 30 kg were restrained in a bag 80 cm in length experiencedby the birds. r991 ROBERTSON:EMPEROR PENGUINS 93

Figure1

A one-personweighing system for EmperorPenguins.

Marking Emperor Penguins for identification two foraging trips at sea. The frozen paint was ignored by the birds and presumably had little effect For identification purposes adults were marked with on the insulation properties of their feathers. In a numbered aluminium flipper band, and the feathers summer, however, the paint did not frenzn on on their ventral surface (above the snow line when application and the birds attempted to preen it from they tobogganed on the sea-ice) was sprayed red their feathers. Therefore this type of marker is 'Super with Enamel' paint (Dulux Australia Ltd.). probably useful only in temperatures low enough to During the colder months the paint froze moments ensure the paint frenz.es quickly when applied. after application but even so residues of it were still Nyanzol-D (Belmar Inc., Massachusetts, USA) evident, as a pink flush through the , up to might be a more suitable marker since it reputedly 60 d later when the penguins had completed at least does not affect feather structure and has lasted at 94 ROBERTSON:EMPEROR PENGUINS Marine Omithologt 1.9

least 2.5 months on foraging Emperor Penguins stomachflushed for an analysis of diet composition ;l (G.L. Kooyman pers. comm.). using the water-flushingtechnique of Wilson (1984). t€ To flush their stomachs I used a manually operated The flipper bands used were designed specially for Handy Pump (Marshall Electronics Inc., USA), a use on Emperor Penguins and were suitably loose on although any pump capable of pumping water would adults during the incubation and chick feeding stages probably suffice (see Wilson 1984). The seawater at of the reproductive cycle, but scarcely fitted around was heated to c. 20oC in a bucket with a high n the swollen flippers of moulting adults. Since bands pressure gas bumer and during the colder months of D of the correct size would be too large for non- the year the pump was kept in the bucket throughout 2 moulting penguins conventional flipper bands should the operation to prevent the water in it from not be used as a permanent marker for Emperor freezing. Water was pumped into the penguin's ; Penguins. Flipper bands could probably be used as stomach through a 10 mm diameter (7 mm intemal) temporary markers on foraging birds provided they Tylon (Imamura Rubber Co., Ltd., Japan) tube :b can be removed well before the moult cycle which was extended90 cm from bill tip to stomach. )\ commences. Note, however, that the chancesof PVC plastic tubing was too brittle in the cold and recapturing banded birds late in the chick-rearing silicone tubing was too soft. pl period will be low, because Emperor Penguins ll attendinglarge chicks spendmost of their time at sea With the water-flushing technique it is especially n feeding and visit the colony to feed their chick for a important not to overfill the penguin's stomach. Of n few hours only. Furthermore, they may not return the 170 adults stomach flushed four died (a further lI to the colony at predictabletime intervals, especially three were distressedto the extent that the procedure if they were traumatized by capture and handling was abandonedand the birds released)from ruptured during the experimentalprocedure. stomachsdue to overfilling. Too much water was introduced berause the food mass (and, in the case l( In studieswhere it is necessaryto band temporarily of subsequentflushings, food and unregurgitated I moulting penguins the bands should be designedto water), and therefore the volume remaining to accommodatethe bandable portion of an Emperor capacity, was not properly considered. The massof I Penguin's flipper of thesedimensions (mean values, food in an Emperor Penguin's stomach not only tr "i s.d. in parentheses,n:4): circumference134 (4.8) varies seasonally but between birds within a season mm, width 56.2 (2.8) mm, thicknessat leading edge (G.G. Robertson unpubl. data), which makes it -i 22.3 (2.8) mm and thicknessat trailing edge 15.9 difficult to rely on results of previous sampling to (2.6) mm. These measurementswere of flippers estimatethe free spacein a penguin's stomach. In I where the swelling appearedto have peaked, and a spite of this, the bird's life will not be jeopardizedif comfortableband should exceedthese dimensions by the food mass is manipulated through the wall of the at least2 mm. abdomen (to gain an appreciation of stomach fill) before each episodeof stomach flushing, and if the The flippers of experimentalchicks were temporarily volume of water introduced is conservative. Filling ;i marked for identification with Velcro hook and loop birds until overflowing (e.g. Offredo & Ridoux nylon fasteners(Linkron Pty Ltd, Australia). These 1986, Klages 1989, initial birds sampled here) I come in a range of bright colours that are easy to see leaves no margin for error should the penguin resist in the colony, are adjustableto accommodateflipper the urge to regurgitate. In this event the only growth and can be numberedwith a felt+ipped pen. warning the bird's stomachmay be reachingcapacity and may rupture is the back pressure felt in the Procuring stomachcontents pump, which may be minimal and would require an alert operator to detect. The risk to the penguin During this study 170 adult Emperor Penguinswere might be reducedby restraining it in the horizontal 1991 ROBERTSON:EMPEROR PENGUINS 95 position, thereby reducing the pressure head of enough water has been administered the tube is water in its stomach. removed and in a single movement the bird is rotated through 1500 over a bucket. With both As a general guide females returning to the colony at hands the operator holds the bird's bill open, the commencement of chick feeding in July with a extends the neck and massages with a finger the mean wet food mass of 1027 g (n:24 birds) in their sphinc0er inside the bird's throat to allow free stomachs were flushed with up to 5 I of water, and passageof the stornachcontents. At the same time a in December adults that were returning with a mean second operator, usually the person pumping the of 21'14 g (n: 12) of food in their stomachsto feed water, applies pressure to the bird's stomach (upside chicks fwo weeks prior to fledging were given up to down at this stage) through the open end of the bag. 3.5 I of water. These estimates are conservative, The penguin then disgorges its stomach contents into since they are based on the largest food mass for the bucket. each period, not on the mean food masses shown above. The advantage of the inverter over more conventional methods is that it supports the bird's A penguin inverter (Fig. 2) was developed to reduce mass, is less tiring for the operator and completely operator effort and stress on the birds during immobilizes the penguin, thereby eliminating the stomach flushing operations. The inverter is a metal time spent restraining the bird. This halves the time frame supporting a eradle shaped to accommodatean spent flushing the stomach, reduces the trauma Emperor Penguin (i.e. wide at the base, narrow at experienced by the bird and requires only two the top). The cradle is lined with a mattress of people instead of three. The inverter would be most sponge rubber embedded in canvas (which prevents suitable for use on Emperor Penguins, because of the bird from destroying the sponge with its feet) their size and strength, but could be used effectively attachedto the cradle by cable ties to protect the bird on King Penguins A. patagonicar, which are also and supported on either side by a stub axle around large and difficult to restrain. In addition the which it can pivot through 1800. A locking device inverter can be used to restrain birds during the on the side nearest the operator locks the cradle in attachment of dive recorders and other devices to either upright, horizontal or inverted positions. The their plumage, and with minor modification to the uprights are joined by a foot plate which prevents cradle to allow access to a flipper could be used to the bird from falling out of the cradle when in the restrain birds while blood samplesare taken. upright position. In practice Emperors rarely stood on this, preferring instead to cling by their toes to Keeping radio-isotopes liquid in sub zaro the bottom rung of the cradle. The penguin is held temperatures in the cradle by four webbing strapswhich passover the bird's back from one side of the cradle to the Tritiated water (3H20), soclium-22 (22Nu) and other, and fastened by Velcro. The vertical Oxygen-18 are used commonly on seabirds to positions of both foot plate and cradle in the frame estimate their rate of food and energy consumption can be adjusted to suit the operator, and the cradle (Green & Gales 1990). Water is used as a carrier and uprights can be removed for transporting. for these isotopes and they are usually transported in the field in glass bottles shielded by tin or lead. To operate the inverter an Emperor Penguin, When used in , where ambient restrainedin a bag, is placed in the cradle locked in temperaturesin winter often fall below -30oC, liquid the horizontal position. The cradle is then pivoted isotopes must be treated with special care to prevent into the upright position and the stomachof the bird them from fr*,nng, which could lead to breakage of fillcd with wann water adopting the normal the glass containers and contamination of the procedurefor the water flushing technique. When surroundinsenvironment. 96 ROBERTSON:EMPEROR PENGUINS Maine Omithologt 19

) ,s ar d 'e t .o p

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l I a

e r n l

Figure 2

Thc penguin inverter showing an Emperor Penguin in the upright and inverted positions. Lettering shows rl points for adjustment or detachment (A), foot plate (B), stomachpump (C) and the cradle locking device (D). I The inset shows an enlarged view of the device that locks the cradle of the penguin inverter with the brokcn n arrowsrndicatins direction of rotation. I 1991 ROBERTSON: EMPERORPENGUINS 97

The isotopes were prevented from freezing by the remaining two birds overbalanced during housing them in a heated wooden box. The 50-cm handling which caused them to spread their legs and square box was made of l2-mm marine plywood and lose their . An alternative method would be to lined with 10-cm of polystyrene foam. The bottles weigh incubating males on a platform balance were contained in a 20-cm sqwrre core in the centre (Jarman 1973, Le Maho er al. 1976), which would of the box and this area was encircled by 20 m of eliminate the need to lift them from the ground. Auto Trace (Chemelex, USA) selfJimiting heater Whichever lechnique is used, egg loss can probably strip (thermal rating 24W/m) which was connected be reduced if the penguins to be weighed are to a portable generator. Heating the central core for selected by subjective appraisal of their just 20 minutes per dey maintained the isotopes temperament, as discussed below for Emperor above 5oC. An 8-kg brass disc, which could be Penguins brooding small chicks. heated on a camping stove, was embedded in the polystyrene under the isotopes in case the generator Regarding abandoned during handling, male failed. Emperor Penguins would rarely retrieve an egg if it was simply placed on the sea-ice a few metres in Inside the box the isotopes were shielded in pots front of them. Of six birds that abandonedtheir egg made from 15 kg of lead (which themselvesretained when handled, five retrieved their egg when it was heat) with a central core large enough to hold a 100- rolled across the sea-ice between their feet. This ml glass bottle of sterile water commonly used to prorpted the bird to scoop the egg onto its feet and dilute isotopes to working strength. The 25-mm into its brood pouch with its bill. Egg rolling was thick walls of these lead pots cut the emission carried out inside the enclosure (so adults could not 22Na, strengthof an emitter of gamma radiation, by mingle with others in the colony) on smooth sea-ice a factor of twenty. with the person rolling the egg prone so the receiving birds attention would be focused more on Handling incubating adults the egg than on the person rolling it.

Incubating males were injected with tritiated water, Handling adults brooding chicks weighed and blood samples and body massestaken serially after release to estimate their rate of mass To estimate food and energy consumption of brood- and fat loss during the incubation fast. Initially six stagechicks with isotopically labelled water, chicks males were weighed in the inverted position and were taken from their parent's brood pouches on restrained on their backs to draw blood samples three occasions (i.e. for isotope injection and to from the ventral surface of the flipper. This collect two subsequent blood samples). However, procedurecaused all the birds to struggle violently removing chicks distressed the brooding adults and and lose their egg; three birds steppedon their egg they would not recover their chick on release. In during restraint while three birds retained their egg July and August abandoned chicks died from but were distressedby handling to the point that they exposurein a few minutes. ahandoncdit on release. Subsequently, brooding adults were selected from Egg loss, and presumably the stress experienced, the colony by subjective appraisal of their was reduced by handling the penguins in the upright temperamentwhile herding them into the enclosure, position. The bag was placed over the bird and tied and by their reaction once in the yard; only birds 'good off beneath it, taking care not to displace the egg that appeared to be parents" were selected. fiom the penguin's feet. The bird was then weighed Typically these birds were in good body condition, by attachingthe scalesto the top of the bag. Of l0 shuffled slowly over the sea-iceeven when prompted birds handled in this way eight retained their egg; to move more quickly, paid repeated attention to 98 ROBERTSON:EMPEROR PENGUINS Maine Omitholog 79 their chick by bowing toward it and vocalizing, by dissecting the foot of a dead penguin. Thus the li reacted aggressively to the person shepherding them efficacy of this technique will depend largely on the ir and were not obviously distressedby being locked in experience of the researcher. On the other hand the hr the yard. Once in the yard adults were restrained in blood vessels beneath the ventral surface of the 6 the standing position with the bag over their upper flipper are prominent, even in extremely cold h bodies while the chick was removed from their feet. weather. Of 17 adults selected in this way 15 endured three e bouts of chick removal and replacement, and The flippers of several dead Emperor Penguins were 3 appeared to feed their chick normally throughout the skinned to examine the position of arteries and veins eight{ay duration of the experiment. Note, (Fig. 3; s€e also Trawa 1970). Externally, the ) however, that this selection procedure may result in brachial arlery at the proximal end of the flipper tr a bias towards older, more experienced breeders and appears as one large vessel, but is in fact an rt may yield results that do not necessarily represent anastomosis of that artery. Attempts to place a the chick-feeding behaviour of the adult population needle in the lumen of one of these blood vessels (see below). failed because the vessels are narrow and mobile, f, and the needle usually rolled off their walls into the sl As a precautionary note, Emperor Penguins are spaces between them. The easiest vessels to draw particulady sensitive to disturbance during the blood from in adults were the radial vein and incubation (when the nrale carries the egg on its feet marginal vein (Fig. 3). This is best done inside a and huddles with other males to conserve body heat) hut or some other shelter by two people, one holding and chick brooding stagesof the reproductive cycle. the penguin upright with a bag covering the head Disturbing incubating males can separate huddling and torso, and the other drawing blood. birds, thereby releasing entrapped heat, and cause eggs to be lost if the birds are prompted to walk too Emperor Penguin chicks up to about four months of quickly. During brooding, which extend'sfor about age were more difficult to bleed than adults because fwo months from hatching, adults accidentally their blood vqsselswere unobtrusive, even when the frightened into walking too quick-ly may spill their down was removed. Blood samples from chicks chick onto the sea-ice where it may frer-Teto death were drawn from either the radial artery or radial or be captured by a nonbreeding bird, only to be vein, which lie in intimate association in the groove abandonedlater and die (Jouventin 1975). Special between the radius and ulna. Due to the closenessof care should be exercised by researchers and these vessels the artery was occasionally punctured, expeditioners when visiting Emperor Penguin but this did not seem adversely to affect the chick. colonies during these two stagesof the reproductive Approaching the vein with the needle at a slightly cycle. oblique angle minimized the chances of the needle rolling off the wall of the vein. Collecting blood samples Attaching dive recorders to foraging birds As for other speciesof penguin, blood samplesfrom Emperor Penguins are usually drawn from veins Adhesives (Heath 1987, Gales et al. l99O), tape beneath the ventral surface of the flipper (Groscolas, (Wilson & Wilson 1989), Velcro (Heath 1987) and et al. 1975,I-e Maho et al. 1977) or from vesselsin worm-drive hose clamps (Kooyman e.t al. 1982, the foot (G. L. Kooyman pers. comm.). Blood Lishman & Croxall 1983) have replaced harnesses vessels in the foot, however, are hidden beneath a (Wilson & Bain 1984) as the preferred methods for thick layer of skin, are constricted in winter and attaching dive recorders to the feathers of penguins must be found by association with external features foraging at sea because they impose less of a of the foot; these features must be learnt beforehand hindrancewhen the birds are divins. However. the r991 ROBERTSON:EMPEROR PENGUINS 99 reliability of these attachment methods could vary based adhesive ('Kwik grip' and 'Bostik'). with the species of penguin and the environment irl Adhesives were allowed to cure for three minutes which it forages. In this study dive recorders were (an approximation of the curing time in the field) at attached with both adhesive and clamps because 5oC before being frozen to -30oC for two hours. other methods of attachment may not have withstood the rigours of the Emperor Penguin foraging regime The devices attached with the cyanoacrylates and (i.e. extended periods at sea, dives in excessof 400 epoxy resins were more difficult to remove from the m and swimming among pack ice). feathers than those attached with the latex-based adhesives. The difference between the To test the bonding strength of adhesives in cyanoacrylates and epoxy adhesives was min61; temperatures below those normally required for overall however, I-octite 401, described by its optimal curing, dummy dive recorders were attached manufacturer as a surface-independent, ultra-fast to the feathers of a dead Emperor Penguin and instant adhesive, achieved a slightly stronger bond froz.en. The adhesives used were cyanoacrylates than the others, and was chosen for subsequent use 'Supaglue'), (I-octite 401, 405 and two-part epoxy in the field. resin (S-minute and 24-hour Araldite) and latex-

RV MV

Figure3

Simplified vcrsion of the main blood vesselsin thc ventral surface of an Emperor Penguin's right flippcr. Stippledarcas show the radius (R), ulna (U) and humcrus (H). Vesselsshown are an anastomoscsof the brachialartery (BA), radial artery (RA), radial vein (RV) and the marginalvein (MV). The circlesindicate prcfcred sitesfor drawing blood samples 100 ROBERTSON:EMPEROR PENGU]NS Maine Ornithologt 79

Dive recorders were attached to the feathers 15 cm to the point where they abandon the colony on P above the tail with four light weight (7 g) worm- release. + drive hose clamps (one on each corner of the device) { and l-octite 401 adhesive. To locate the birds on ACKNOWLEDGEMENTS o their return to the colony a small radio transmitter P n was glued to the feathers between the shoulders and The project de.scribed was conducted by permit an area of the bird's plumage was painted as granted under Section 19 of the Antarctic Treaty I. described above. Of 57 dive recorders deployed on (Environment Protection) Act, 1980 of Australia. I penguins between July and December, 3l birds thank members of the 35th ANARE to Mawson for 2 returned to feed their chicks. each with devices assistencein the field and for discussions about some firmly in place even though some penguins spent up of the methods presented. I am grateful to Tony c to 65 d at sea and dived below 400 m. Everett for his thoughts on the design of the penguin f: inverter and to Arthur Alexander for making it. I c The remaining experimental penguins presumably appreciate comments by Brian Green, Norbert T.W. I abandoned the colony as no marked penguins were Klages, Gerry L. Kooyman, Michael D. Whitehead, F found without dive recorders despite intensive Yolanda M. van Heezik and Eric J. Woehler on t searching neaily every day of the sampling period. drafts. Margret Jacksondrew the figures. p The abandonment rate (devices lost as a percentage of the number deployed) increased through the chick REFERENCES \ growing period, and ranged from O% (n:10) in I July (males, post-hatching), 20% (n:10) in early GALES, R., W]LLIAMS, C. & RITZ, D. 1990. d September,44% (n: 18) in mid October and 89% Foraging behaviour of the , a (n: 19) for birds captured during the first two days minor: initial results and assessment of December. This trend does not follow the pattern of instrument effect. J. 7ttol.. Lond. 22O: 6l- of chick mortality (Robertson in press) so the 85. experimental birds being released from parental GREEN, B. & GALES, R. 1990. Water, sodium duties cannot explain why many adults carrying and energy furnover in free-living penguins: a devices abandoned their chicks. Presumably the review. In: DAVIS, L.S. & DARBY, J.T. failure of these birds to return to the colony reflects, (Eds.). Penguin biology. San Diego: Academic at least in part, their reaction to the trauma of Press.pp. 245-268. capture,handling and attachmentof devices(see also GROSCOLAS, R., CHARPENTIER, C. & Wilson et aL 1989, Galeset al. l99O\. LEMONNIER F. 1975. Variation de la concentrationdes acidesamines libres du plasma One way of mrnimizing the effect of this problem au cours du cycle reproducteurchez le Manchot would be to selectfor foraging behaviourstudies the empereur, forsteri. Comp. least timid birds, for theseare usually the easieston Biochem. Physiol. 5lB: 5147. which to conduct experiments (l* Maho et al. HEATH, R.G.M. 1987. A method for attaching 1977). Typically, instead of toboganning away transmittersto penguins. J. WiAL Manage. 5l: when approachedby people theseindividuals remain 399-401. upright and vocalize vigorously during attempts to JARMAN, M. 1973. Experimentson the Emperor capture them. However, where estimates of Penguin, Aptenodytesforsteri, in various thermal ecological parameters are to be extended to the environments. Br. Antarct. Surv. Bull. 33134: .population, a random method of selectionwould be 5743. necesury, and the importance of this must be JOUVENTIN, P. 1975. Mortality parametcrsin weighed against the risk of investing expensive Emperor Penguins Aptenodytes forsteri. In: devicesin birds that mav be distressedbv handlins STONEHOUSE, B. (Ed.). The biology of r99l ROBERTSON:EMPEROR PENGUINS 101

penguins. l-ondon: Macmillan Press. pp 435- OFFREDO, C. & RIDOUX, V. 1986. The diet of 446. Emperor Penguins Aptenodytes forsteri in Adelie KLAGES, N.T.W. 1989. Food and feedingecology I:nd, Antarctica. Ibis 128:. 409413. of Emperor Penguins in the easternWeddell Sea. PREVOST, J. 1961. Ecologie du Manchot Polar Biol.9: 385-390. empereur. Actualites scientifiques et KOOYMAN, G.L., DAVIS, R.W., CROXALL, industrielles. Paris: Hermann. J.P. & COSTA, D.P. 1982. Diving depthsand ROBERTSON, G.G. in press. Population siz.e energy requirements of King Penguins. Science and breeding success of Emperor Penguins at the 217: 726-727. Ausler and Taylor Glacier colonies, Mawson LE MAHO. Y., DELCLIT'TE, P. & Coast, Antarctica. . CHATONNET, I. 1976. in TRAWA, G. 1970. Note prdliminaire sur la fasting Emperor Penguins under natural vascularisation des membres des spheniscides. conditions. Amer. J. Physiol. 23l 913-922. Oiseau 4O: 142-156. LE MAHO, Y., DELCLITTE, P. & GROSCOLAS, WII-SON, R.P. 1984. An improved stomach pump R. 1977. Body temperature regulation of the for penguins and other seabirds. J. Fiel.d Emperor Penguin (Aptenodytesforsteri) during Ornithol. 55: 109-113. physiological fasting. In: LLANO, G.A. (Ed.). WI[-SON, R.P. & BAIN, C.R. 1984. AN Adaptations within antarctic ecosystems.. inexpe.nsivedepth gauge for penguins. J. W|AL Washington: Smithsonian Institute. pp. 50 1-509. Manage. 48: 1077-1084. LISHMAN G.S. & CROXALL, J.P. 1983. Diving WILSON, R.P. & WILSON, M.-P. 1989. Tape: a depths of the \tgoscelis package-attachment technique for penguins. antardica. Br. Antarcl. Surv.Bull.6l:21-25. WiAn. Soc.Bull. l7:77-79.