Surviving in the Ross Sea

Surviving in the Ross Sea

Emperor penguins and Weddell seals are the only marine predators that breath air and live year round in Antarctica Ross Sea. How these two animals are able to live among each other when there diets, hunting depths and area distribution are shared is the question. Ross Sea is called home by six emperor penguin colonies, approximately 180,000 birds, and about 50,000 Weddell seals. It is important, when considering competition between these two species to know that each share above and below water resources however it is below water prey where problems may occur. Several items can be considered to determine true competition overlap. These items include prey selection, using different hunting depths and habitat separation.

Fish account for most of the diet of both predators (99.3 % for seals and 89-95% for penguins). To take it one step further, Pleuragramma antarcticum, or Antarctica silverfish is the primary prey for each. Of the fish consumed, 88.6% of penguin's fish diet and 99.3% of the seals diet consist of the Antarctic silverfish. This species of penguins and seals do not select fish of different classes despite body and mouth size difference. Seal prey is slightly larger, yet still considered juvenile as are penguin prey. Absence of larger prey in the penguin diet may be due to the fact that all samples were collected during chick rearing periods. It is possible that adult birds would capture larger fish for themselves and return with slightly smaller sizes for their young. Although seals and penguins hunt for the same size and species of fish, this does not restrict them from cohabitation.

Next we will consider the depth at which they hunt. Both, seal and penguins are excellent divers. In order to dive at great depths, these species move oxygen away from the lungs and into the muscles and blood. This allows them to store 3-4 times more oxygen than the average land mammal. In addition, seals and penguins use other techniques to reduce oxygen intake. Examples of this include the reduction of heart rates during long dives and an energy conserving swim pattern called burst and glide. It is known that penguins and seals have the ability to reach similar depths, however, the time below surface varies between the two animals. What we don't know is the depth each prefer, or under ice swimming habits of the P. antarcticum. ADL or aerobic dive limit (amount