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Research Objectives:
The Emperor penguin, Aptenodytes forsteri, is the premier avian diver and a top predator in the antarctic ecosystem. The routine occurrence of 500-meter dives during foraging trips is a physiological and behavioral enigma. Project researchers will attempt to determine how and why Emperor penguins dive as deeply and long as they do by examining four major topics: pressure tolerance, management of oxygen stores, end-organ tolerance of diving hypoxemia/ischemia, and deep-dive foraging behavior. These subjects are relevant to the role of the Emperor as a top predator in the antarctic ecosystem and to critical concepts in diving physiology, including decompression sickness, nitrogen narcosis, shallow water blackout, hypoxemic tolerance, and extension of aerobic dive time.
The core of this season's project will be the Penguin Ranch, a sea ice camp for the study Emperor penguins' diving. Other work will include the censuses of the Emperor colonies by aerial photography over Beaufort Island, Franklin Island, and Cape Washington. Day trips will be conducted to the Cape Crozier colony, and (sea-ice permitting) the Beaufort Island colony. Project team members will deploy a long-term camera at Cape Crozier.
Microprocessor based instruments and cameras will be attached to birds, enabling researchers to determine feeding behavior, stroke frequency, diving air volume, oxygen depletion rates, and nitrogen profiles during diving. Biochemical investigations of biopsied tissue samples will also allow study of molecular adaptations to tissue hypoxia. In addition to investigation of mechanisms of hypoxemic and pressure tolerance, these studies will refine techniques for examination of diving behavior of Emperors at sea during the final year of the grant.
The final objective of the project is to continue annual censuses at Emperor colonies in the Ross Sea, and in particular, to follow the effects of the B-15 iceberg on the Cape Crozier colony. This is especially important because of recent declines in the last year: 6,000 fewer chicks at Cape Washington, only 300 chicks at Beaufort Island, and less than 200 chicks at Cape Crozier. Long-term monitoring of the Cape Crozier colony will also be evaluated with the deployment of a remote, programmable camera in this season.
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