Export 95 results:
Sort by: Author [ Title  (Asc)] Type Year
A B C D E F G H I J K L M N O P Q R S T U V W X Y Z 
Ponganis, PJ, Kreutzer U, Sailasuta N, Knower T, Hurd R, Jue T.  2002.  Detection of myoglobin desaturation in Mirounga angustirostris during apnea. American Journal of Physiology-Regulatory Integrative and Comparative Physiology. 282:R267-R272. AbstractWebsite

H-1 NMR solution-state study of elephant seal (Mirounga angustirostris) myoglobin (Mb) and hemoglobin (Hb) establishes the temperature-dependent chemical shifts of the proximal histidyl NdeltaH signal, which reflects the respective intracellular and vascular PO2 in vivo. Both proteins exist predominantly in one major isoform and do not exhibit any conformational heterogeneity. The Mb and Hb signals are detectable in M. angustirostris tissue in vivo. During eupnea M. angustirostris muscle maintains a well-saturated MbO(2). However, during apnea, the deoxymyoglobin proximal histidyl NdeltaH signal becomes visible, reflecting a declining tissue PO2. The study establishes a firm methodological basis for using NMR to investigate the metabolic responses during sleep apnea of the elephant seal and to secure insights into oxygen regulation in diving mammals.

Ponganis, PJ, Kooyman GL, Castellini MA.  1993.  Determinants of the aerobic dive limit of Weddell seals: analysis of diving metabolic rates, postdive end tidal PO2's, and blood and muscle oxygen stores. Physiological Zoology. 66:732-749. AbstractWebsite

The mean aerobic dive limit (ADL) for Weddell seals was calculated from data collected on diving metabolic rates (VO2) and blood and muscle O2 stores. Mean diving VO2 of adult seals during predominantly exploratory dive patterns was 4.5 mL O2 kg-1 min-1; mean VO2 of a subadult seal engaged in foraging dive bouts was 8.5 mL O2 kg-1 min-1. The adult value was 30% greater than that used in past ADL calculations. Mean plasma volume was 7% body mass (BM); blood volume calculated with the highest hematocrit (Hct) observed (66) was 21% BM. Hemoglobin concentration at such an Hct was 26% by weight. End tidal PO2 (pre- and postdive) justified the use of 95% and 20% arterial O2 saturations in the blood O2 store calculation. Total blood O2 stores were 50% greater than those used in past ADL calculations. Mean myoglobin concentration (5.4% by weight) and more recent anatomical estimates of muscle mass yielded a 35% increase in muscle O2 stores. The mean estimated ADL for a 450-kg seal calculated with these new data was 19.1 min, 2.3 min greater than in past calculations and only 1 min less than the 20-min inflection point of the curve of dive duration versus postdive lactic acid appearance. For the subadult engaged in foraging dives, the mean estimated ADL was about 9 min, again quite similar to past ADL calculations.

Ponganis, PJ, Starke LN, Horning M, Kooyman GL.  1999.  Development of diving capacity in emperor penguins. Journal of Experimental Biology. 202:781-786. AbstractWebsite

To compare the diving capacities of juvenile and adult emperor penguins Aptenodytes forsteri, and to determine the physiological variables underlying the diving ability of juveniles, we monitored diving activity in juvenile penguins fitted with satellite-linked time/depth recorders and examined developmental changes in body mass (M-b), hemoglobin concentration, myoglobin (Mb) content and muscle citrate synthase and lactate dehydrogenase activities, Diving depth, diving duration and time-at-depth histograms were obtained from two fledged juveniles during the first 2.5 months after their departure from the Cape Washingon colony in the Ross Sea, Antarctica. During this period, values of all three diving variables increased progressively. After 8-10 weeks at sea, 24-41% of transmitted maximum diving depths were between 80 and 200 m, Although most dives lasted less than 2 min during the 2 month period, 8-25% of transmitted dives in the last 2 weeks lasted 2-4 min. These values are lower than those previously recorded in adults during foraging trips. Of the physiological variables examined during chick and juvenile development, only M-b and Mb content did not approach adult values, In both near-hedge chicks and juveniles, Mb was 50-60% of adult values and Mb content was 24-31% of adult values. This suggests that the increase in diving capacity of juveniles at sea will be most dependent on changes in these factors.

Eckert, SA, Eckert KL, Ponganis P, Kooyman GL.  1989.  Diving and foraging behavior of leatherback sea turtles (Dermochelys coriacea). Canadian Journal of Zoology-Revue Canadienne De Zoologie. 67:2834-2840.   10.1139/z89-399   AbstractWebsite

Remote time–depth recorders (TDR) were deployed on six gravid leatherbacks nesting on Sandy Point, St. Croix. Dive behavior was monitored continuously for each turtle during internesting intervals ranging from 9 to 11 days. Dive duration averaged 9.9 min/dive (SD = 5.3, n = 5096); mean depth was 61.6 m (SD = 59.1, n = 5096). One turtle dived twice beyond the range of her TDR to depths we estimate >1000 m. Postdive surfacing intervals averaged 4.9 min/dive (SD = 13.1, n = 5090). Differences in mean dive depth, dive duration, and surface intervals among turtles were not attributable to differences in body size (length or mass). Distinct diel periodicity was observed in dive behavior; submergence intervals were longest at dawn, declined throughout the day, and were shortest at dusk. Night dives (19:00–04:59) were shorter, shallower, and more frequent than day dives (05:00–18:59). Dive depth was less variable at night than during the day. The dive pattern suggests nocturnal foraging within the deep scattering layer, a hypothesis that is corroborated by seasonal weight loss data.

Kooyman, GL, Ponganis PJ, Howard RS.  1999.  Diving Animals. The lung at depth. ( Lundgren CEG, Miller JN, Eds.).:587-620., New York: Marcel Dekker Abstract
Ponganis, PJ.  2011.  Diving Mammals. Comprehensive Physiology. 1: John Wiley & Sons, Inc.   10.1002/cphy.c091003   AbstractWebsite

The ability of diving mammals to forage at depth on a breath hold of air is dependent on gas exchange, both in the lung and in peripheral tissues. Anatomical and physiological adaptations in the respiratory system, cardiovascular system, blood and peripheral tissues contribute to the remarkable breath-hold capacities of these animals. The end results of these adaptations include efficient ventilation, enhanced oxygen storage, regulated transport and delivery of respiratory gases, extreme hypoxemic/ischemic tolerance, and pressure tolerance. © 2011 American Physiological Society. Compr Physiol 1:447-465, 2011.

Ponganis, PJ, Kooyman GL.  2000.  Diving physiology of birds: a history of studies on polar species. Comparative Biochemistry and Physiology a-Molecular and Integrative Physiology. 126:143-151.   10.1016/s1095-6433(00)00208-7   AbstractWebsite

Our knowledge of avian diving physiology has been based primarily on research with polar species. Since Scholander's 1940 monograph, research has expanded from examination of the 'diving reflex' to studies of free-diving birds, and has included laboratory investigations of oxygen stores, muscle adaptations, pressure effects, and cardiovascular/metabolic responses to swimming exercise. Behavioral and energetic studies at sea have shown that common diving durations of many avian species exceed the calculated aerobic diving limits (ADL). Current physiological research is focused on factors, such as heart rate and temperature, which potentially affect the diving metabolic rate and duration of aerobic diving. (C) 2000 Elsevier Science Inc. All rights reserved.

Ponganis, PJ, Kooyman GL.  1990.  Diving physiology of penguins. Acta XX Congressus Internationalis Ornithologici, Christchurch, New Zealand, 2-9 December 1990. ( Butler PJ, Jones DR, Eds.).:6., Wellington, N.Z.: New Zealand Ornithological Congress Trust Board Abstract
Shiomi, K, Sato K, Mitamura H, Arai N, Naito Y, Ponganis PJ.  2008.  Effect of ocean current on the dead-reckoning estimation of 3-D dive paths of emperor penguins. Aquatic Biology. 3:265-270.   10.3354/ab00087   AbstractWebsite

The dead-reckoning technique is a useful method for obtaining 3-D movement data of aquatic animals. However, such positional data include an accumulative error. Understanding the source of the error is important for proper data interpretation. In order to determine whether ocean currents affect dive paths calculated by dead-reckoning, as has previously been hypothesized, we examined the directions of the estimated positions relative to the known real points (error direction) and the relationship between the error direction and the current direction. 3-D dive paths of emperor penguins Aptenodytes forsteri diving at isolated dive holes in eastern McMurdo Sound were reconstructed by dead-reckoning, and the net error and error direction were calculated. The net error correlated positively with the dive duration. The error directions were not distributed uniformly, and the mean error direction tended to be north of the starting point of dives. Because there was a southward-flowing current in eastern McMurdo Sound, the ocean current was likely to affect the calculated dive paths. Therefore, the method of error correction generally used, in which the net error divided by the dive duration is applied to each estimated position, is realistically appropriate, provided that the current does not change significantly during a dive.

Kooyman, GL, Ainley DG, Ballard G, Ponganis PJ.  2007.  Effects of giant icebergs on two emperor penguin colonies in the Ross Sea, Antarctica. Antarctic Science. 19:31-38.   10.1017/s0954102007000065   AbstractWebsite

The arrival in January 2001 in the south-west Ross Sea of two giant icebergs, C16 and Bl5A, subsequently had dramatic affects on two emperor penguin colonies. B15A collided with the north-west tongue of the Ross Ice Shelf at Cape Crozier, Ross Island, in the following months and destroyed the penguins' nesting habitat. The colony totally failed in 2001, and years after, with the icebergs still in place, exhibited reduced production that ranged from 0 to 40% of the 1201 chicks produced in 2000. At Beaufort Island, 70 km NW of Crozier, chick production declined to 6% of the 2000 count by 2004. Collisions with the Ross Ice Shelf at Cape Crozier caused incubating adults to be crushed, trapped in ravines, or to abandon the colony and, since 2001, to occupy poorer habitat. The icebergs separated Beaufort Island from the Ross Sea Polynya, formerly an easy route to feeding and wintering areas. This episode has provided a glimpse of events which have probably occurred infrequently since the West Antarctic Ice Sheet began to retreat 12 000 years ago. The results allow assessment of recovery rates for one colony decimated by both adult and chick mortality, and the other colony by adult abandonment and chick mortality.

Ponganis, PJ, McDonald BI, Tift MS, Gonzalez SC, DaValle B, Gliniecki RA, Stehman CC, Hauff N, Ruddick B, Howard R.  2017.  Effects of inhalational anesthesia on blood gases and pH in California sea lions. Marine Mammal Science. 33:726-737.   10.1111/mms.12388   AbstractWebsite

Despite the widespread use of inhalational anesthesia with spontaneous ventilation in many studies of otariid pinnipeds, the effects and risks of anesthetic-induced respiratory depression on blood gas and pH regulation are unknown in these animals. During such anesthesia in California sea lions (Zalophus californianus), blood gas and pH analyses of opportunistic blood samples revealed routine hypercarbia (highest P-CO2 = 128 mm Hg [17.1 kPa]), but adequate arterial oxygenation (P-O2 > 100 mm Hg [13.3 kPa] on 100% inspiratory oxygen). Respiratory acidosis (lowest pH = 7.05) was limited by the increased buffering capacity of sea lion blood. Amarkedly widened alveolar-to-arterial P-O2 difference was indicative of atelectasis and ventilation-perfusion mismatch in the lung secondary to hypoventilation during anesthesia. Despite the generally safe track record of this anesthetic regimen in the past, these findings demonstrate the value of high inspiratory O-2 concentrations and the necessity of constant vigilance and caution. In order to avoid hypoxemia, we emphasize the importance of late extubation or at least maintenance of mask ventilation on O-2 until anesthetic-induced respiratory depression is resolved. In this regard, whether for planned or emergency application, we also describe a simple, easily employed intubation technique with the Casper zalophoscope for sea lions.

Jobsis, PD, Ponganis PJ, Kooyman GL.  2001.  Effects of training on forced submersion responses in harbor seals. Journal of Experimental Biology. 204:3877-3885. AbstractWebsite

In several pinniped species, the heart rates observed during unrestrained dives are frequently higher than the severe bradycardias recorded during forced submersions. To examine other physiological components of the classic 'dive response' during such moderate bradycardias, a training protocol was developed to habituate harbor seals (Phoca vitulina) to short forced submersions. Significant changes were observed between physiological measurements made during naive and trained submersions (3-3.5min). Differences were found in measurements of heart rate during submersion (naive 18 +/-4.3 beats min(-1) versus trained 35 +/-3.4 beats min(-1)), muscle blood flow measured using laser-Doppler flowmetry (naive 1.8 +/-0.8 ml min(-1) 100 g(-1) versus trained 5.8 +/-3.9 ml min(-1) 100 g(-1)), change in venous P-O 2 (naive -0.44 +/-1.25 kPa versus trained -1.48 +/-0.76 kPa) and muscle deoxygenation rate (naive -0.67 +/-0.27 mvd s(-1) versus trained -0.51 +/-0.18 mvd s(-1), a relative measure of muscle oxygenation provided by the Vander Niroscope, where mvd are milli-vander units). In contrast to the naive situation, the post-submersion increase in plasma lactate levels was only rarely significant in trained seals. Resting eupneic (while breathing) heart rate and total oxygen consumption rates (measured in two seals) were not significantly different between the naive and trained states. This training protocol revealed that the higher heart rate and greater muscle blood flow in the trained seals were associated with a lower muscle deoxygenation rate, presumably secondary to greater extraction of blood O-2 during trained submersions. Supplementation of muscle oxygenation by blood O-2 delivery during diving would increase the rate of blood O-2 depletion but could prolong the duration of aerobic muscle metabolism during diving. This alteration of the dive response may increase the metabolic efficiency of diving.

Tift, MS, Ponganis PJ, Crocker DE.  2014.  Elevated carboxyhemoglobin in a marine mammal, the northern elephant seal. Journal of Experimental Biology. 217:1752-1757.   10.1242/jeb.100677   AbstractWebsite

Low concentrations of endogenous carbon monoxide (CO), generated primarily through degradation of heme from hemeproteins, have been shown to maintain physiological function of organs and to exert cytoprotective effects. However, high concentrations of carboxyhemoglobin (COHb), formed by CO binding to hemoglobin, potentially prevent adequate O-2 delivery to tissues by lowering arterial O-2 content. Elevated heme-protein concentrations, as found in marine mammals, are likely associated with greater heme degradation, more endogenous CO production and, consequently, elevated COHb concentrations. Therefore, we measured COHb in elephant seals, a species with large blood volumes and elevated hemoglobin and myoglobin concentrations. The levels of COHb were positively related to the total hemoglobin concentration. The maximum COHb value was 10.4% of total hemoglobin concentration. The mean (+/- s.e.m.) value in adult seals was 8.7 +/- 0.3% (N=6), while juveniles and pups (with lower heme-protein contents) had lower mean COHb values of 7.6 +/- 0.2% and 7.1 +/- 0.3%, respectively (N=9 and N=9, respectively). Serial samples over several hours revealed little to no fluctuation in COHb values. This consistent elevation in COHb suggests that the magnitude and/ or rate of heme-protein turnover is much higher than in terrestrial mammals. The maximum COHb values from this study decrease total body O-2 stores by 7%, thereby reducing the calculated aerobic dive limit for this species. However, the constant presence of elevated CO in blood may also protect against potential ischemia-reperfusion injury associated with the extreme breath-holds of elephant seals. We suggest the elephant seal represents an ideal model for understanding the potential cytoprotective effects, mechanisms of action and evolutionary adaptation associated with chronically elevated concentrations of endogenously produced CO.

Kooyman, GL, Ponganis PJ.  1994.  Emperor penguin oxygen consumption, heart rate and plasma lactate levels during graded swimming exercise. Journal of Experimental Biology. 195:199-209. AbstractWebsite

Oxygen consumption (V-O2), heart rate and blood chemistry were measured in four emperor penguins, Aptenodytes forsteri (Gray), during graded swimming exercise. The maximum V-O2, obtained, 52ml O-2 kg(-1) min(-1), was 7.8 times the measured resting V-O2 of 6.7 ml O-2 kg(-1) min(-1) and 9.1 times the predicted resting V-O2. As the swimming effort rose, a linear increase in surface and submerged heart rates (fH) occurred. The highest average maximum surface and submersion heart rates of any bird were 213 and 210 beats min(-1), respectively. No increase in plasma lactate concentrations occurred until V-O2 was greater than 25 ml O-2 kg(-1) min(-1). At the highest V-O2 values measured, plasma lactate concentration reached 9.4 mmol l(-1). In comparison with other animals of approximately the same mass, the aerobic capacity of the emperor penguin is less than those of the emu and dog but about the same as those of the seal, sea lion and domestic goat. For aquatic animals, a low aerobic capacity seems to be consistent with the needs of parsimonious oxygen utilization while breath-holding.

Sato, K, Ponganis PJ, Habara Y, Naito Y.  2005.  Emperor penguins adjust swim speed according to the above-water height of ice holes through which they exit. Journal of Experimental Biology. 208:2549-2554.   10.1242/jeb.01665   AbstractWebsite

Emperor penguins leap from the water onto the sea ice. Their ability to reach above-water height depends critically on initial vertical speed of their leaping, assuming that the kinetic energy is converted to gravitational potential energy. We deliberately changed the above-water heights of ice hole exits, in order to examine whether penguins adjusted swim speed in accordance with the above-water height of the ice. Penguins were maintained in a corral on the fast ice in Antarctica, and voluntarily dived through two artificial ice holes. Data loggers were deployed on the penguins to monitor under water behavior. Nine instrumented penguins performed 386 leaps from the holes during experiments. The maximum swim speeds within 1 s before the exits through the holes correlated significantly with the above-water height of the holes. Penguins adopted higher speed to exit through the higher holes than through the lower holes. Speeds of some failed exits were lower than the theoretical minimum values to reach a given height. Penguins failed to exit onto the sea ice in a total of 37 of the trials. There was no preference to use lower holes after they failed to exit through the higher holes. Rather, swim speed was increased for subsequent attempts after failed leaps. These data demonstrated that penguins apparently recognized the above-water height of holes and adopted speeds greater than the minimal vertical speeds to reach the exit height. It is likely, especially in the case of higher holes (>40 cm), that they chose minimum speeds to exit through the holes to avoid excess energy for swimming before leaping. However, some exceptionally high speeds were recorded when they directly exited onto the ice from lower depths. In those cases, birds could increase swim speed without strokes for the final seconds before exit and they only increased the steepness of their body angles as they surfaced, which indicates that the speed required for leaps by emperor penguins were aided by buoyancy, and that penguins can sometimes exit through the ice holes without any stroking effort before leaping.

Nagy, KA, Kooyman GL, Ponganis PJ.  2001.  Energetic cost of foraging in free-diving emperor penguins. Physiological and Biochemical Zoology. 74:541-547.   10.1086/322165   AbstractWebsite

Hypothesizing that emperor penguins (Aptenodytes forsteri) would have higher daily energy expenditures when foraging for their food than when being hand-fed and that the increased expenditure could represent their foraging cost, we measured field metabolic rates (FMR; using doubly labeled water) over 4-d periods when 10 penguins either foraged under sea ice or were not allowed to dive but were fed fish by hand. Surprisingly, penguins did not have higher rates of energy expenditure when they dove and captured their own food than when they did not forage but were given food. Analysis of time-activity and energy budgets indicated that FMR was about 1.7 x BMR (basal metabolic rate) during the 12 h d(-1) that penguins were lying on sea ice. During the remaining 12 h d(-1), which we termed their "foraging period" of the day, the birds were alert and active (standing, preening, walking, and either free diving or being hand-fed), and their FMR was about 4.1 x BMR. This is the lowest cost of foraging estimated to date among the eight penguin species studied. The calculated aerobic diving limit (ADL(C)), determined with the foraging period metabolic rate of 4.1 x BMR and known O-2 stores, was only 2.6 min, which is far less than the 6-min ADL previously measured with postdive lactate analyses in emperors diving under similar conditions. This indicates that calculating ADL(C) from an at-sea or foraging-period metabolic rate in penguins is not appropriate. The relatively low foraging cost for emperor penguins contributes to their relatively low total daily FMR (2.9 x BMR). The allometric relationship for FMR in eight penguin species, including the smallest and largest living representatives, is kJ d(-1) = 1,185 kg(0.705).

Ancel, A, Starke LN, Ponganis PJ, Van Dam R, Kooyman GL.  2000.  Energetics of surface swimming in Brandt's cormorants (Phalacrocorax penicillatus Brandt). Journal of Experimental Biology. 203:3727-3731. AbstractWebsite

The energy requirements of Brandt's cormorants (Phalacrocorax penicillatus) during surface swimming were measured in birds swimming under a metabolic chamber in a water flume. From the oxygen consumption recordings, we extrapolated the metabolic rate and cost of transport at water speeds ranging from 0 to 1.3 ms(-1). In still water, the birds' mean mass-specific rate of oxygen consumption ((V)over dot(O2),) while floating at the surface was 20.2ml O-2 min(-1) kg(-1), 2.1 times the predicted resting metabolic rate. During steady-state voluntary swimming against a how, their Po, increased with water speed, reaching 74 mi O-2 min(-1) kg(-1) at 1.3 ms(-1), which corresponded to an increase in metabolic rate from 11 to 25 W kg(-1). The cost of transport decreased,vith swimming velocity, approaching a minimum of 19 J kg(-1) m(-1) for a swimming speed of 1.3 m s(-1) Surface swimming in the cormorant costs approximately 18% less than sub-surface swimming. This confirms similar findings in tufted ducks (Aythya fuligula) and supports the hypothesis that increased energy requirements are necessary in these bird diving to overcome buoyancy and heat submergence.

Barber-Meyer, SM, Kooyman GL, Ponganis PJ.  2007.  Estimating the relative abundance of emperor penguins at inaccessible colonies using satellite imagery. Polar Biology. 30:1565-1570.   10.1007/s00300-007-0317-8   AbstractWebsite

Emperor penguin (Aptenodytes forsteri) populations are useful environmental indicators due to the bird's extreme reliance on sea ice. We used remote sensing technology to estimate relative adult bird abundance at two inaccessible emperor penguin colonies in the Ross Sea, Antarctica. We performed supervised classification of 12 panchromatic satellite images of the seven known Ross Sea colonies. We used regression to predict adult bird counts at the inaccessible colonies by relating the number of pixels classified as "penguin" in the satellite images of the accessible colonies to corresponding known adult bird counts from aerial photographs or ground counts. While our analysis was hampered by excessive guano and shadows, we used satellite imagery to differentiate between relatively small (< 3,000 adult birds) and larger colonies (> 5,000 adult birds). Remote sensing technology is logistically less intense and less costly than aerial or ground censuses when the objective is to document penguin presence and/or large emperor penguin population changes (e.g., catastrophic changes). Improvements expected soon in the resolution of the satellite images should allow for more accurate abundance estimates.

Meir, JU, Champagne CD, Costa DP, Williams CL, Ponganis PJ.  2009.  Extreme hypoxemic tolerance and blood oxygen depletion in diving elephant seals. American Journal of Physiology-Regulatory Integrative and Comparative Physiology. 297:R927-R939.   10.1152/ajpregu.00247.2009   AbstractWebsite

Meir JU, Champagne CD, Costa DP, Williams CL, Ponganis PJ. Extreme hypoxemic tolerance and blood oxygen depletion in diving elephant seals. Am J Physiol Regul Integr Comp Physiol 297: R927-R939, 2009. First published July 29, 2009; doi: 10.1152/ajpregu.00247.2009.-Species that maintain aerobic metabolism when the oxygen (O(2)) supply is limited represent ideal models to examine the mechanisms underlying tolerance to hypoxia. The repetitive, long dives of northern elephant seals (Mirounga angustirostris) have remained a physiological enigma as O(2) stores appear inadequate to maintain aerobic metabolism. We evaluated hypoxemic tolerance and blood O(2) depletion by 1) measuring arterial and venous O(2) partial pressure (PO(2)) during dives with a PO(2)/temperature recorder on elephant seals, 2) characterizing the O(2) hemoglobin (O(2)-Hb) dissociation curve of this species, 3) applying the dissociation curve to PO(2) profiles to obtain %Hb saturation (SO(2)), and 4) calculating blood O(2) store depletion during diving. Optimization of O(2) stores was achieved by high venous O(2) loading and almost complete depletion of blood O(2) stores during dives, with net O(2) content depletion values up to 91% (arterial) and 100% (venous). In routine dives (>10 min) Pv(O2) and Pa(O2) values reached 2-10 and 12-23 mmHg, respectively. This corresponds to SO(2) of 1-26% and O(2) contents of 0.3 (venous) and 2.7 ml O(2)/dl blood (arterial), demonstrating remarkable hypoxemic tolerance as PaO(2) is nearly equivalent to the arterial hypoxemic threshold of seals. The contribution of the blood O(2) store alone to metabolic rate was nearly equivalent to resting metabolic rate, and mean temperature remained near 37 degrees C. These data suggest that elephant seals routinely tolerate extreme hypoxemia during dives to completely utilize the blood O(2) store and maximize aerobic dive duration.

Blight, LK, Ainley DG, Ackley SF, Ballard G, Ballerini T, Brownell RL, Cheng CHC, Chiantore M, Costa D, Coulter MC, Dayton P, Devries AL, Dunbar R, Earle S, Eastman JT, Emslie SD, Evans CW, Garrott RA, Kim S, Kooyman G, Lescroel A, Lizotte M, Massaro M, Olmastroni S, Ponganis PJ, Russell J, Siniff DB, Smith WO, Stewart BS, Stirling I, Willis J, Wilson P, Woehler EJ.  2010.  Fishing for data in the Ross Sea. Science. 330:1316-1316.   10.1126/science.330.6009.1316   AbstractWebsite
Tift, MS, Huckstadt LA, McDonald BI, Thorson PH, Ponganis PJ.  2017.  Flipper stroke rate and venous oxygen levels in free-ranging California sea lions. Journal of Experimental Biology. 220:1533-1540.   10.1242/jeb.152314   AbstractWebsite

The depletion rate of the blood oxygen store, development of hypoxemia and dive capacity are dependent on the distribution and rate of blood oxygen delivery to tissues while diving. Although blood oxygen extraction by working muscle would increase the blood oxygen depletion rate in a swimming animal, there is little information on the relationship between muscle workload and blood oxygen depletion during dives. Therefore, we examined flipper stroke rate, a proxy of muscle workload, and posterior vena cava oxygen profiles in four adult female California sea lions (Zalophus californianus) during foraging trips at sea. Flipper stroke rate analysis revealed that sea lions minimized muscle metabolism with a stroke-glide strategy when diving, and exhibited prolonged glides during the descent of deeper dives (>100 m). During the descent phase of these deep dives, 55 +/- 21% of descent was spent gliding, with the longest glides lasting over 160 s and covering a vertical distance of 340 m. Animals also consistently glided to the surface from 15 to 25 m depth during these deeper dives. Venous hemoglobin saturation (SO2) profiles were highly variable throughout dives, with values occasionally increasing during shallow dives. The relationship between SO2 and flipper stroke rate was weak during deeper dives, while this relationship was stronger during shallow dives. We conclude that (1) the depletion of oxygen in the posterior vena cava in deep-diving sea lions is not dependent on stroke effort, and (2) stroke-glide patterns during dives contribute to a reduction of muscle metabolic rate.

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.

Cristofari, R, Bertorelle G, Ancel A, Benazzo A, Lemaho Y, Ponganis PJ, Stenseth NC, Trathan PN, Whittington JD, Zanetti E, Zitterbart DP, Le Bohec C, Trucchi E.  2016.  Full circumpolar migration ensures evolutionary unity in the Emperor penguin. Nature Communications. 7   10.1038/ncomms11842   AbstractWebsite

Defining reliable demographic models is essential to understand the threats of ongoing environmental change. Yet, in the most remote and threatened areas, models are often based on the survey of a single population, assuming stationarity and independence in population responses. This is the case for the Emperor penguin Aptenodytes forsteri, a flagship Antarctic species that may be at high risk continent-wide before 2100. Here, using genome-wide data from the whole Antarctic continent, we reveal that this top-predator is organized as one single global population with a shared demography since the late Quaternary. We refute the view of the local population as a relevant demographic unit, and highlight that (i) robust extinction risk estimations are only possible by including dispersal rates and (ii) colony-scaled population size is rather indicative of local stochastic events, whereas the species' response to global environmental change is likely to follow a shared evolutionary trajectory.

Goforth, H, Ponganis PJ, Eggerton E.  1987.  Glycogenolytic responses and force production characteristics of a bottlenose dolphin (Tursiops truncatus). Seventh biennial Conference on the Biology of Marine Mammals, abstracts, December 5-9, 1987, Miami, Florida. :1., Miami, FL: s.n. Abstract
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.