Publications

Export 3 results:
Sort by: Author Title Type [ Year  (Desc)]
2014
Kooyman, GL, Ponganis PJ.  2014.  Chick production at the largest emperor penguin colony decreases by 50% from 2008-10. Antarctic Science. 26:33-37.   10.1017/s0954102013000515   AbstractWebsite

The emperor penguin colony at Coulman Island is reputedly the largest known. This reputation is based on intermittent ground and aerial surveys performed since 1958. From an aerial survey obtained on 28 October 2010 we discovered that the total number of chicks was 56% of the lowest previous estimate of 2006 and only 41% of the most recent estimate in 2008. All of the counts tallied since 1983 were determined either by ground counts or from aerial film or digital photographs, or estimates from adult counts. We also determined the sea ice conditions in autumn, which is close to the time the adults arrive to breed. We present three hypotheses of what might have happened from 2008-10 to cause the step change in chick production, the small recovery of chick numbers in 2011, and the complete recovery of number of adults from 2010-11. We conclude that local circumstances may have strongly influenced the breeding behaviour of the emperor penguins in 2010 and to a lesser degree in 2011 when many adults elected not to breed.

2001
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.

1998
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.