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Knower Stockard, T, Heil J, Meir JU, Sato K, Ponganis KV, Ponganis PJ.  2005.  Air sac P-O2 and oxygen depletion during dives of emperor penguins. Journal of Experimental Biology. 208:2973-2980.   10.1242/jeb.01687   AbstractWebsite

In order to determine the rate and magnitude of respiratory O-2 depletion during dives of emperor penguins (Aptenodytes forsteri), air sac O-2 partial pressure (PO2) was recorded in 73 dives of four birds at an isolated dive hole. These results were evaluated with respect to hypoxic tolerance, the aerobic dive limit (ADL; dive duration beyond which there is post-dive lactate accumulation) and previously measured field metabolic rates (FMRs). 55% of dives were greater in duration than the previously measured 5.6-min ADL. P-O2 and depth profiles revealed compression hyperoxia and gradual O-2 depletion during dives. 42% of final P(O2)s during the dives (recorded during the last 15 s of ascent) were < 20 mmHg (< 2.7 kPa). Assuming that the measured air sac P-O2 is representative of the entire respiratory system, this implies remarkable hypoxic tolerance in emperors. In dives of durations greater than the ADL, the calculated end-of-dive air sac O-2 fraction was < 4%. The respiratory O-2 store depletion rate of an entire dive, based on the change in O-2 fraction during a dive and previously measured diving respiratory volume, ranged from I to 5 ml O-2 kg(-1) min(-1) and decreased exponentially with diving duration. The mean value, 2.1 +/- 0.8 ml O-2 kg(-1) min(-1), was (1) 19-42% of previously measured respiratory O-2 depletion rates during forced submersions and simulated dives, (2) approximately one-third of the predicted total body resting metabolic rate and (3) approximately 10% of the measured FMR. These findings are consistent with a low total body metabolic rate during the dive.

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.  1997.  The challenges of diving to depth. American Scientist. 85:530-539. AbstractWebsite
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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.

Kooyman, G, Ponganis PJ.  1990.  Behavior and physiology of diving in emperor and king penguins. Penguin biology. ( Davis L, Darby JT, Eds.).:14., San Diego: Academic Press Abstract
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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.

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.

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.

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.

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
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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.

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.