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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
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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.