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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.

Ponganis, PJ, Stockard TK, Meir JU, Williams CL, Ponganis KV, Van Dam RP, Howard R.  2007.  Returning on empty: extreme blood O-2 depletion underlies dive capacity of emperor penguins. Journal of Experimental Biology. 210:4279-4285.   10.1242/jeb.011221   AbstractWebsite

Blood gas analyses from emperor penguins (Aptenodytes forsteri) at rest, and intravascular P-O2 profiles from free-diving birds were obtained in order to examine hypoxemic tolerance and utilization of the blood O-2 store during dives. Analysis of blood samples from penguins at rest revealed arterial P(O2)s and O-2 contents of 68 +/- 7 mmHg (1 mmHg= 133.3 Pa) and 22.5 +/- 1.3 ml O-2 dl(-1) (N= 3) and venous values of 41 +/- 10 mmHg and 17.4 +/- 2.9 ml O-2 dl(-1) (N= 9). Corresponding arterial and venous Hb saturations for a hemoglobin (Hb) concentration of 18 g dl(-1) were > 91% and 70%, respectively. Analysis of P-O2 profiles obtained from birds equipped with intravascular P-O2 electrodes and backpack recorders during dives revealed that (1) the decline of the final blood P-O2 of a dive in relation to dive duration was variable, (2) final venous P-O2 values spanned a 40-mmHg range at the previously measured aerobic dive limit (ADL; dive duration associated with onset of post-dive blood lactate accumulation), (3) final arterial, venous and previously measured air sac P-O2 values were indistinguishable in longer dives, and (4) final venous P-O2 values of longer dives were as low as 1-6 mmHg during dives. Although blood O-2 is not depleted at the ADL, nearly complete depletion of the blood O-2 store occurs in longer dives. This extreme hypoxemic tolerance, which would be catastrophic in many birds and mammals, necessitates biochemical and molecular adaptations, including a shift in the O-2-Hb dissociation curve of the emperor penguin in comparison to those of most birds. A relatively higher-affinity Hb is consistent with blood P-O2 values and O-2 contents of penguins at rest.

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.