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Ancel, A, Kooyman GL, Ponganis PJ, Gendner JP, Lignon J, Mestre X, Huin N, Thorson PH, Robisson P, Lemaho Y.  1992.  Foraging behaviour of emperor penguins as a resource detector in winter and summer. Nature. 360:336-339.   10.1038/360336a0   AbstractWebsite

The emperor penguin (Aptenodytes forsteri), which feeds only at sea, is restricted to the higher latitudes of the antarctic sea-ice habitat1-3. It breeds on the winter fast ice when temperatures are -30-degrees-C and high winds are frequent3. Assuming entirely the task of incubating the single egg, the male fasts for about 120 days in the most severe conditions. When it is relieved by the female around hatching time, the distance between the colony and the open sea may be 100 km or more4,5, but where emperors go to forage at that time or during the summer is unknown. The polynias are areas of open water in sea-ice and during winter, with the under-ice habitats at any time of the year, they are among the most difficult of all Antarctic areas to sample. Here we monitor by satellite the routes taken by emperor penguins for foraging and compare them with satellite images of sea-ice. Winter birds walking over fast ice travelled up to 296 km to feed in polynias, whereas those swimming in light pack-ice travelled as far as 895 km from the breeding colony. One record of diving showed that although most dives are to mid-water depths, some are near the bottom. Obtaining such detailed information on foraging in emperor penguins means that this bird now offers a unique opportunity to investigate the Antarctic sea-ice habitat.

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Ponganis, PJ, Kooyman GL.  1999.  Heart rate and electrocardiogram characteristics of a young California gray whale (Eschrichtius robustus). Marine Mammal Science. 15:1198-1207.   10.1111/j.1748-7692.1999.tb00885.x   AbstractWebsite

Electrocardiogram (ECG) analyses of Holter monitor recordings from a young California gray whale were performed to determine ECG waveform characteristics, evaluate the heart rate pattern for sinus arrhythmia, obtain resting heart rates at known body masses as the whale increased in size, and compare those heart rates with predicted heart rates from allometric equations. The PR and QRS intervals (475 +/- 35 msec, 208 +/- 24 msec, respectively, n = 20) support the concept (Meijler et al. 1992) that atrioventricular transmission and ventricular excitation times do not increase linearly in very large mammals. A sinus arrhythmia pattern at rest (apneic heart rates of 15-25 beats per min [bpm] and eupneic heart rates of 34-40 bpm) is consistent with a relative eupneic tachycardia and apneic bradycardia during diving activity of whales. The heart rate-body mass measurements (35-24 bpm at body masses of 3,531-8,200 kg) in this study (1) extend the range of allometric heart rate and body mass data in mammals a full order of magnitude, to almost 10,000 kg, (2) support the use of allometric equations (based primarily on mammals <1,000 kg in body mass) in estimating resting heart rates in whales, and (3) demonstrate that previously reported heart rates in large whales are not representative of resting heart rate, probably secondary to circumstances during measurement.

Ponganis, PJ, Kooyman GL, Winter LM, Starke LN.  1997.  Heart rate and plasma lactate responses during submerged swimming and trained diving in California sea lions, Zalophus californianus. Journal of Comparative Physiology B-Biochemical Systemic and Environmental Physiology. 167:9-16.   10.1007/s003600050042   AbstractWebsite

California sea lions, Zalophus californianus, were trained to elicit maximum voluntary breath holds during stationary underwater targeting, submerged swimming, and trained diving. Lowest heart rate during rest periods was 57 bpm. The heart rate profiles in all three protocols were dominated by a bradycardia of 20-50 bpm, and demonstrated that otariid diving heart rates were at or below resting heart rate. Venous blood samples were collected after submerged swimming periods of 1-3 min. Plasma lactate began to increase only after 2.3-min submersions. This rise in lactate and our inability to train sea lions to dive or swim submerged for periods longer than 3 min lead us to conclude that an aerobic limit had been reached. Due to the similarity of heart rate responses and swimming velocities recorded during submerged swimming and trained diving, this 2.3-min limit should approximate the aerobic dive limit in these 40-kg sea lions. Total body O-2 stores, based on measurements of blood and muscle O-2 stores in these animals, and prior lung O-2 Store analyses, were 37-43 ml O-2 kg(-1). The aerobic dive limit, calculated with these O-2 stores and prior measurements of at-sea metabolic rates of sea lions, is 1.8-2 min, similar to that measured by the change in post-submersion lactate concentration.

Kooyman, GL, Ponganis PJ, Castellini MA, Ponganis EP, Ponganis KV, Thorson PH, Eckert SA, Lemaho Y.  1992.  Heart rates and swim speeds of Emperor penguins diving under sea ice. Journal of Experimental Biology. 165:161-180. AbstractWebsite

Heart rate during overnight rest and while diving were recorded from five emperor penguins with a microprocessor-controlled submersible recorder. Heart rate, cardiac output and stroke volume were also measured in two resting emperor penguins using standard electrocardiography and thermodilution measurements. Swim velocities from eight birds were obtained with the submersible recorder. The resting average of the mean heart rates was 72 beats min-1. Diving heart rates were about 15% lower than resting rates. Cardiac outputs of 1.9-2.9 ml kg-1 s-1 and stroke volumes of 1.6-2.7 ml kg-1 were similar to values recorded from mammals of the same body mass. Swim velocities averaged 3 m s-1. The swim speeds and heart rates suggest that muscle O2 depletion must occur frequently: therefore, many dives require a significant energy contribution from anaerobic glycolysis.

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Kooyman, GL, Ponganis PJ.  2004.  The icing of external recorders during the polar winter. Memoirs of National Institute of Polar Research Special Issue. 58:183-187. AbstractWebsite
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Kooyman, GL, Ponganis PJ.  2007.  The initial journey of juvenile emperor penguins. Aquatic Conservation-Marine and Freshwater Ecosystems. 17:S37-S43.   10.1002/aqc.930   AbstractWebsite

1. The first major journey of emperor penguins, among several in their lifetime, is the juveniles' dispersal from their natal colony on a trip that takes them beyond Antarctic waters. The route taken by fledglings from Cape Washington (74.5 degrees S; 165.4 degrees E) was Studied by applying satellite transmitters to ten individuals during December 1994-1996. In January 2001 transmitters with longer transmission capacity were also applied to six hand-fed fledglings, which had been held captive for one month while attaining a body mass exceeding that of wild birds. These post-captive birds were released at the ice edge of McMurdo Sound (77.5 degrees S; 165.0 degrees E), which is in the vicinity of other emperor penguin colonies, and 320km south of their natal colony of Cape Washington. 2. Independent of their parents, the wild birds travelled north-east for the next two months, reaching locations as low as 57 degrees S. The post-captive birds travelled north also, but their trek reached only to about 63 degrees S before they turned south, or remained near their most northerly position from March through May. 3. It was concluded that among colonies in the southern Ross Sea: (a) most healthy fledglings Survive at least the first two months at sea, feeding themselves as they go; (b) the Cape Washington fledglings travelled as far north as 57 degrees S, and much of this journey was in ice free waters; (c) by April, the post-captive birds reached at least as far as the large-scale pack ice edge and possibly beyond the edge Lit 63 degrees S; (d) by early March the trend north ends, and by about late March the birds travel to, or remain near the northern ice edge. 4. The reason the birds travel so far north remains a mystery. Copyright (c) 2008 John Wiley & Sons, Ltd.

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Castellini, MA, Kooyman GL, Ponganis PJ.  1992.  Metabolic rates of freely diving Weddell seals: correlations with oxygen stores, swim velocity and diving duration. Journal of Experimental Biology. 165:181-194. AbstractWebsite

The metabolic rates of freely diving Weddell seals were measured using modern methods of on-line computer analysis coupled to oxygen consumption instrumentation. Oxygen consumption values were collected during sleep, resting periods while awake and during diving periods with the seals breathing at the surface of the water in an experimental sea-ice hole in Antarctica. Oxygen consumption during diving was not elevated over resting values but was statistically about 1.5 times greater than sleeping values. The metabolic rate of diving declined with increasing dive duration, but there was no significant difference between resting rates and rates in dives lasting up to 82 min. Swimming speed, measured with a microprocessor velocity recorder, was constant in each animal. Calculations of the aerobic dive limit of these seals were made from the oxygen consumption values and demonstrated that most dives were within this theoretical limit. The results indicate that the cost of diving is remarkably low in Weddell seals relative to other diving mammals and birds.

Ponganis, PJ, Kooyman GL, Castellini MA.  1995.  Multiple sightings of Arnouxs beaked whales along the Victoria Land coast. Marine Mammal Science. 11:247-250.   10.1111/j.1748-7692.1995.tb00523.x   AbstractWebsite
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Ponganis, PJ, Kooyman GL, Castellini MA, Ponganis EP, Ponganis KV.  1993.  Muscle temperature and swim velocity profiles during diving in a Weddell seal, Leptonychotes weddellii. Journal of Experimental Biology. 183:341-346. AbstractWebsite

Locomotory muscle temperature and swim velocity profiles of an adult Weddell seal were recorded over a 21 h period. The highest temperatures occurred during a prolonged surface period (mean 37.3-degrees-C, S.D. 0.16-degrees-C). Muscle temperature averaged 36.8 and 36.6-degrees-C (S.D. 0.25-degrees-C, 0.19-degrees-C) during two dive bouts and showed no consistent fluctuations between dive and interdive surface intervals. Swim velocities were also constant, near 1.3 m s-1. These data indicate that past records of low aortic temperatures (35-degrees-C) during and after prolonged dives are not indicative of whole-body temperature changes, and that muscle temperature, even during dives as long as 45 min, remains near 37-degrees-C.

Dolar, MLL, Suarez P, Ponganis PJ, Kooyman GL.  1999.  Myoglobin in pelagic small cetaceans. Journal of Experimental Biology. 202:227-236. AbstractWebsite

Although myoglobin (Mb) is considered to contribute significantly to the oxygen and diving capacity of marine mammals, few data are available for cetaceans, Cetacean by-catch in the tuna driftnet fisheries in the Sulu Sea, Philippines, afforded the opportunity to examine Mb content and distribution, and to determine muscle mass composition, in Fraser's (Lagenodelphis hosei) and spinner (Stenella longirostris) dolphins and a pygmy killer whale (Feresa attenuata). Age was estimated by body length determination. Stomach contents were analyzed for the presence or absence of milk and solid foods. It was hypothesized (a) that Mb concentration ([Mb]) would be higher in Fraser's and spinner dolphins than in other small cetaceans because of the known mesopelagic distribution of their prey, (b) that [Mb] would vary among different muscles according to function during diving, and (c) that [Mb] would increase with age during development. The results were as follows. ii) Myoglobin concentrations of the longissimus muscle in adult Fraser's (6.8-7.2 g 100 g(-1) muscle) and spinner (5-6 g 100 g(-1) muscle) dolphins and in an immature pygmy killer whale (5.7 g 100 g(-1) muscle) were higher than those reported previously for small cetaceans, (2) [Mb] varied significantly among the different muscle types in adult dolphins but not in calves; in adults, swimming muscles had significantly higher [Mb] than did non-swimming muscles, contained 82-86 % of total Mb, and constituted 75-80 % of total muscle mass. (3) Myoglobin concentrations in Fraser's and spinner dolphins increased with size and age and were 3-4 times greater in adults than in calves, The high Mb concentrations measured in the primary locomotory muscles of these pelagic dolphins are consistent with the known mesopelagic foraging behaviour of Fraser's and spinner dolphins and suggest that the pygmy killer whale is also a deep-diving species. The high Mb concentrations in epaxial, hypaxial and abdominal muscle groups also support the primary locomotory functions suggested for these muscles in other anatomical studies. As in other species. the increase in [Mb] during development probably parallels the development of diving capacity.

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Kooyman, GL, Ponganis PJ.  1998.  The physiological basis of diving to depth: Birds and mammals. Annual Review of Physiology. 60:19-32.   10.1146/annurev.physiol.60.1.19   AbstractWebsite

There is wide diversity in the animals that dive to depth and in the distribution of their body oxygen stores. A hallmark of animals diving to depth is a substantial elevation of muscle myoglobin concentration. In deep divers, more than 80% of the oxygen store is in the blood and muscles. How these oxygen stores are managed, particularly within muscle, is unclear. The aerobic endurance of four species has now been measured. These measurements provide a standard for other species in which the limits cannot be measured. Diving to depth requires several adaptations to the effects of pressure. In mammals, one adaptation is lung collapse at shallow depths, which limits absorption of nitrogen. Blood Nz levels remain below the threshold for decompression sickness. No such adaptive model is known for birds. There appear to be two diving strategies used by animals that dive to depth. Seals, for example, seldom rely on anaerobic metabolism. Birds, on the other hand, frequently rely on anaerobic metabolism to exploit prey-rich depths otherwise unavailable to them.

Ponganis, PJ, Kooyman GL, Van Dam R, Lemaho Y.  1999.  Physiological responses of king penguins during simulated diving to 136 m depth. Journal of Experimental Biology. 202:2819-2822. AbstractWebsite

To evaluate blood N-2 uptake and the role of the respiratory volume (air sacs/lungs) as a N-2 and O-2 reservoir in deep-diving penguins, diving respiratory volume (V-DR), heart rate (f(H)), venous P-N2, blood volume (V-b) and hemoglobin (Hb) concentration were measured in king penguins (Aptenodytes patagonicus) during forced submersions and compressions equivalent to depths up to 136 m, V-DR was 69+/-18 ml kg(-1) (mean +/- S.D.) in 62 submersions ranging from 4.4 atmospheres absolute (ATA; 1 ATA=101 kPa) (34 m) to 14.6 ATA (136 m), Submersion f(H) averaged 30+/-7 beats min(-1) (N=18), approximately 20% of pre- and post-submersion values. Venous P-N2 values during and after submersions as deep as 11.2 ATA (102 m) were all less than 2.8 atmospheres N-2 (283 kPa) above ambient pressure, a previously measured threshold for symptomatic bubble formation. Mean V-b was 83+/-8 ml kg(-1) (N=6); [Hb] was 17.6+/-0.7 g dl(-1) (N=7), On a mass-specific basis, mean V-DR, and therefore total available N-2, is 41% of that in shallow-diving penguin species. Total body O-2 stores, calculated from measured V-DR, V-b, [Hb], muscle mass and myoglobin concentration, are 45 ml kg(-1), with 23 % in the respiratory system. This small respiratory fraction in comparison with that in shallow-diving penguins suggests a lesser reliance on the respiratory oxygen store for extended breath-holding and also a reduced uptake of nitrogen at depth.

Ponganis, PJ, Kooyman GL, Sartoris D, Jobsis P.  1992.  Pinniped splenic volumes. American Journal of Physiology. 262:R322-R325. AbstractWebsite

Splenic volume was measured by computerized axial tomography in three harbor seals (Phoca vitulina) and two California sea lions (Zalophus californianus). Volumes ranged from 228 to 679 ml, representing 0.8-3.0% of calculated percentage body mass. Despite possible variation in the state of splenic contraction during the examination, these values are in the upper range of reported mammalian splenic volumes (as % of body mass). This reinforces the pinniped splenic erythrocyte storage concept.

Ponganis, PJ, Kooyman GL, Starke LN, Kooyman CA, Kooyman TG.  1997.  Post-dive blood lactate concentrations in emperor penguins, Aptenodytes forsteri. Journal of Experimental Biology. 200:1623-1626. AbstractWebsite

In order to determine an aerobic diving limit (ADL) in emperor penguins (Aptenodytes forsteri), post-dive blood lactate concentrations were measured in penguins foraging at an isolated sea ice hole. Resting lactate concentrations were 1.2-2.7 mmol l(-1). Serial samples revealed that lactate level usually peaked within 5 min after dives and that 7-12 min was required for lactate concentrations to decrease from 5-8 mmol l(-1) to less than 2.5 mmol l(-1). Post-dive lactate level was not elevated above 3 mmol l(-1) for dives shorter than 5 min. Two-phase regression analysis revealed a transition at 5.6 min in the post-dive lactate level versus diving duration relationship. All dives longer than 7 min were associated with lactate concentrations greater than 5 mmol l(-1). We conclude that the ADL in emperor penguins ranges between 5 and 7 min. These are the first determinations of post-dive lactate concentrations in any free-diving bird and are currently the only physiological assessment of an ADL in an avian species.

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Ponganis, PJ, Van Dam RP, Levenson DH, Knower T, Ponganis KV, Marshall G.  2003.  Regional heterothermy and conservation of core temperature in emperor penguins diving under sea ice. Comparative Biochemistry and Physiology a-Molecular & Integrative Physiology. 135:477-487.   10.1016/s1095-6433(03)00133-8   AbstractWebsite

Temperatures were recorded at several body sites in emperor penguins (Aptenodytes forsteri) diving at an isolated dive hole in order to document temperature profiles during diving and to evaluate the role of hypothermia in this well-studied model of penguin diving physiology. Grand mean temperatures (+/-S.E.) in central body sites during dives were: stomach: 37.1 +/- 0.2 degreesC (n = 101 dives in five birds), pectoral muscle: 37.8 +/- 0.1 degreesC (n = 71 dives in three birds) and axillary/brachial veins: 37.9 +/- 0.1 degreesC (n = 97 dives in three birds). Mean diving temperature and duration correlated negatively at only one site in one bird (femoral vein, r = -0.59, P < 0.05; range < 1 degreesC). In contrast, grand mean temperatures in the wing vein, foot vein and lumbar subcutaneous tissue during dives were 7.6 +/- 0.7 degreesC (n = 157 dives in three birds), 20.2 +/- 1.2 degreesC (n = 69 in three birds) and 35.2 +/- 0.2 degreesC (n = 261 in six birds), respectively. Mean limb temperature during dives negatively correlated with diving duration in all six birds (r = -0.29 to -0.60, P < 0.05). In two of six birds, mean diving subcutaneous temperature negatively correlated with diving duration (r = -0.49 and -0.78, P < 0.05). Sub-feather temperatures decreased from 31 to 35 T during rest periods to a grand mean of 15.0 +/- 0.7 degreesC during 68 dives of three birds; mean diving temperature and duration correlated negatively in one bird (r = -0.42, P < 0.05). In general, pectoral, deep venous and even stomach temperatures during diving reflected previously measured vena caval temperatures of 37-39 degreesC more closely than the anterior abdominal temperatures (19-30 degreesC) recently recorded in diving emperors. Although prey ingestion can result in cooling in the stomach, these findings and the lack of negative correlations between internal temperatures and diving duration do not support a role for hypothermia-induced metabolic suppression of the abdominal organs as a mechanism of extension of aerobic dive time in emperor penguins diving at the isolated dive hole. Such high temperatures within the body and the observed decreases in limb, anterior abdomen, subcutaneous and sub-feather temperatures are consistent with preservation of core temperature and cooling of an outer body shell secondary to peripheral vasoconstriction, decreased insulation of the feather layer, and conductive/convective heat loss to the water environment during the diving of these emperor penguins. (C) 2003 Elsevier Science Inc. All fights reserved.

Kooyman, GL, Ponganis PJ.  2017.  Rise and fall of Ross Sea emperor penguin colony populations: 2000 to 2012. Antarctic Science. 29:201-208.   10.1017/s0954102016000559   AbstractWebsite

There are seven emperor penguin (Aptenodytes forsteri) colonies distributed throughout the traditional boundaries of the Ross Sea from Cape Roget to Cape Colbeck. This coastline is c. 10% of the entire coast of Antarctica. From 2000 to 2012, there has been a nearly continuous record of population size of most, and sometimes all, of these colonies. Data were obtained by analysing aerial photographs. We found large annual variations in populations of individual colonies, and conclude that a trend from a single emperor penguin colony may not be a good environmental sentinel. There are at least four possibilities for census count fluctuations: i) this species is not bound to a nesting site like other penguins, and birds move within the colony and possibly to other colonies, ii) harsh environmental conditions cause a die-off of chicks in the colony or of adults elsewhere, iii) the adults skip a year of breeding if pre-breeding foraging is inadequate and iv) if sea ice conditions are unsatisfactory at autumn arrival of the adults, they skip breeding or go elsewhere. Such variability indicates that birds at all Ross Sea colonies should be counted annually if there is to be any possibility of understanding the causes of population changes.

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Sato, K, Watanuki Y, Takahashi A, Miller PJO, Tanaka H, Kawabe R, Ponganis PJ, Handrich Y, Akamatsu T, Watanabe Y, Mitani Y, Costa DP, Bost CA, Aoki K, Amano M, Trathan P, Shapiro A, Naito Y.  2007.  Stroke frequency, but not swimming speed, is related to body size in free-ranging seabirds, pinnipeds and cetaceans. Proceedings of the Royal Society B-Biological Sciences. 274:471-477.   10.1098/rspb.2006.0005   AbstractWebsite

It is obvious, at least qualitatively, that small animals move their locomotory apparatus faster than large animals: small insects move their wings invisibly fast, while large birds flap their wings slowly. However, quantitative observations have been difficult to obtain from free-ranging swimming animals. We surveyed the swimming behaviour of animals ranging from 0.5 kg seabirds to 30 000 kg sperm whales using animal-borne accelerometers. Dominant stroke cycle frequencies of swimming specialist seabirds and marine mammals were proportional to mass(-0.29) (R-2=0.99, n=17 groups), while propulsive swimming speeds of 1-2 m s(-1) were independent of body size. This scaling relationship, obtained from breath-hold divers expected to swim optimally to conserve oxygen, does not agree with recent theoretical predictions for optimal swimming. Seabirds that use their wings for both swimming and flying stroked at a lower frequency than other swimming specialists of the same size, suggesting a morphological trade-off with wing size and stroke frequency representing a compromise. In contrast, foot-propelled diving birds such as shags had similar stroke frequencies as other swimming specialists. These results suggest that muscle characteristics may constrain swimming during cruising travel, with convergence among diving specialists in the proportions and contraction rates of propulsive muscles.

Sato, K, Shiomi K, Marshall G, Kooyman GL, Ponganis PJ.  2011.  Stroke rates and diving air volumes of emperor penguins: implications for dive performance. Journal of Experimental Biology. 214:2854-2863.   10.1242/jeb.055723   AbstractWebsite

Emperor penguins (Aptenodytes forsteri), both at sea and at an experimental dive hole, often have minimal surface periods even after performance of dives far beyond their measured 5.6 min aerobic dive limit (ADL: dive duration associated with the onset of post-dive blood lactate accumulation). Accelerometer-based data loggers were attached to emperor penguins diving in these two different situations to further evaluate the capacity of these birds to perform such dives without any apparent prolonged recovery periods. Minimum surface intervals for dives as long as 10 min were less than 1 min at both sites. Stroke rates for dives at sea were significantly greater than those for dives at the isolated dive hole. Calculated diving air volumes at sea were variable, increased with maximum depth of dive to a depth of 250 m, and decreased for deeper dives. It is hypothesized that lower air volumes for the deepest dives are the result of exhalation of air underwater. Mean maximal air volumes for deep dives at sea were approximately 83% greater than those during shallow (<50 m) dives. We conclude that (a) dives beyond the 5.6. min ADL do not always require prolongation of surface intervals in emperor penguins, (b) stroke rate at sea is greater than at the isolated dive hole and, therefore, a reduction in muscle stroke rate does not extend the duration of aerobic metabolism during dives at sea, and (c) a larger diving air volume facilitates performance of deep dives by increasing the total body O(2) store to 68 ml O(2) kg(-1). Although increased O(2) storage and cardiovascular adjustments presumably optimize aerobic metabolism during dives, enhanced anaerobic capacity and hypoxemic tolerance are also essential for longer dives. This was exemplified by a 27.6 min dive, after which the bird required 6 min before it stood up from a prone position, another 20 min before it began to walk, and 8.4 h before it dived again.

Ponganis, PJ, Costello ML, Starke LN, MathieuCostello O, Kooyman GL.  1997.  Structural and biochemical characteristics of locomotory muscles of emperor penguins, Aptenodytes forsteri. Respiration Physiology. 109:73-80.   10.1016/s0034-5687(97)84031-5   AbstractWebsite

Structural and biochemical characteristics of the primary muscles used for swimming (pectoralis, PEC and supracoracoideus, SC) were compared to those of leg muscles in emperor penguins (Aptenodytes forsteri). The mass of PEG-SC was four times that of the leg musculature, and mitochondrial volume density in PEC and SC (4%) was two-thirds that in sartorius (S) and gastrocnemius. The differences in muscle mass and mitochondrial density yielded a 2.2-fold greater total mitochondrial content in PEG-SC than leg muscles, which appears to account for the 1.8-fold greater whole-body highest oxygen consumption previously recorded in emperor penguins during swimming compared to walking. Calculation of maximal mitochondrial O-2 consumption in PEG-SC and leg muscle yielded values of 5.8-6.9 mi O-2 ml(-1) min(-1), which are similar to those in locomotory muscles of most mammals and birds. A distinct feature of emperor penguin muscle was its myoglobin content, with concentrations in PEG-SC (6.4 g 100 g(-1)) among the highest measured in any species. This resulted in a PEG-SC O-2 store greater than that of the entire blood. In addition, ratios of myoglobin content to mitochondrial volume density and to citrate synthase activity were 4.4 and 2.5 times greater in PEG than in S, indicative of the significant role of myoglobin in the adaptation of muscle to cardiovascular adjustments during diving. (C) 1997 Elsevier Science B.V.

Ponganis, PJ, Van Dam RP, Marshall G, Knower T, Levenson DH.  2000.  Sub-ice foraging behavior of emperor penguins. Journal of Experimental Biology. 203:3275-3278. AbstractWebsite

Emperor penguins (Aptenodytes forsteri) were equipped with a remote underwater video camera, the Crittercam, to evaluate sub-ice foraging behavior while the birds dived from an isolated dive hole. Three birds dived and foraged successfully for Ih periods after being trained to wear and to dive with a harness for camera attachment. Video and depth profile recordings revealed that emperor penguins travel at shallow depths (<50 m), ascend to the undersurface of the ice to feed on fish, and descend back to depth to return to the exit hole. Although the mean durations of dives of individual birds with the Crittercam were 21-35 % shorter than the diving durations of these same birds without the camera, the dive profiles in both situations were similar, thus demonstrating a similar foraging strategy in birds diving without the camera. Despite shorter diving durations with the camera, the penguins were still successful at prey capture in 80 % of 91 dives greater than 1 min in duration. Prey included the sub-ice fish Pagothenia borchgrevinki. Hunting ascents (from depth to within 5 m of the surface) occurred in 85 % of dives, ranged from zero to three per dive, and were associated with successful prey capture in 77 % of 128 ascents, Occasionally, several fish were captured during a single ascent, These observations and this application of video technology create a model for further physiological and behavioral studies of foraging, and also emphasize the potential importance of shallow dives as sources of food intake for emperor penguins during foraging trips to sea.

Ponganis, PJ, Ponganis EP, Ponganis KV, Kooyman GL, Gentry RL, Trillmich F.  1990.  Swimming velocities in otariids. Canadian Journal of Zoology-Revue Canadienne De Zoologie. 68:2105-2112.   10.1139/z90-293   AbstractWebsite

Velocities during surface swimming and diving were measured with microprocessor recorders in four otariid species: northern fur seals (Callorhinusursinus), Galapagos sea lions (Zalophuscalifornianuswollebaeki), Galapagos fur seals (Arctocephalusgalapagoensis), and Hooker's sea lions (Phocarctoshookeri). Mean surface swimming velocities ranged from 0.6 to 1.9 m/s. Transit distances to feeding sites (1.2–90 km) were calculated using these velocities. Dive velocities, recorded every 15 s, ranged from 0.9 to 1.9 m/s. These velocities were consistent with calculated minimal cost of transport velocities in the smaller species. Using time partitioning, the metabolic cost of a northern fur seal foraging trip is estimated on the basis of recorded velocities and their calculated energy costs. This value is within 6% of that previously made with doubly labeled water techniques.

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Ponganis, PJ, Van Dam RP, Knower T, Levenson DH.  2001.  Temperature regulation in emperor penguins foraging under sea ice. Comparative Biochemistry and Physiology a-Molecular and Integrative Physiology. 129:811-820.   10.1016/s1095-6433(01)00349-x   AbstractWebsite

Inferior vena caval (IVC) and anterior abdominal (AA) temperatures were recorded in seven emperor penguins (Aptenodytes foresteri) foraging under sea ice in order to evaluate the hypothesis that hypothermia-induced metabolic suppression might extend aerobic diving time. Diving durations ranged from 1 to 12.5 min, with 39% of dives greater than the measured aerobic dive limit of 5.6 min. Anterior abdominal temperature decreased progressively throughout dives, and partially returned to pre-dive values during surface intervals. The lowest AA temperature was 19 degreesC. However, mean AA temperatures during dives did not correlate with diving durations. In six of seven penguins, only minor fluctuations in IVC temperatures occurred during diving. These changes were often elevations in temperature. In the one exception, although IVC temperatures decreased, the reductions were less than those in the anterior abdomen and did not correlate with diving durations. Because of these findings, we consider it unlikely that regional hypothermia in emperor penguins leads to a significant reduction in oxygen consumption of the major organs within the abdominal core. Rather, temperature profiles during dives are consistent with a model of regional heterothermy with conservation of core temperature, peripheral vasoconstriction, and cooling of an outer body shell. (C) 2001 Elsevier Science Inc. All rights reserved.

Barber-Meyer, SM, Kooyman GL, Ponganis PJ.  2008.  Trends in western Ross Sea emperor penguin chick abundances and their relationships to climate. Antarctic Science. 20:3-11.   10.1017/s0954102007000673   AbstractWebsite

The emperor penguin (Aptenodytes forsteri) is extremely dependent on the extent and stability of sea ice, which may make the species particularly susceptible to environmental change. In order to appraise the stability of the emperor penguin populations at six colonies in the western Ross Sea, we used linear regression analysis to evaluate chick abundance trends (1983-2005) and Pearson's r correlation to assess their relation to two local and two large-scale climate variables. We detected only one significant abundance trend; the Cape Roget colony increased from 1983 to 1996 (n = 6). Higher coefficients of variation in chick abundances at smaller colonies (Cape Crozier, Beaufort Island, Franklin Island) suggest that such colonies occupy marginal habitat, and are more susceptible to environmental change. We determined chick abundance to be most often correlated with local Ross Sea climate variables (sea ice extent and sea surface temperature), but not in consistent patterns across the colonies. We propose that chick abundance is most impacted by fine scale sea ice extent and local weather events, which are best evaluated by on-site assessments. We did not find sufficient evidence to reject the hypothesis that the overall emperor penguin population in the Ross Sea was stable during this period.