Most of them feed on krill and on one another. Many have developed special adaptations to survive in the extreme cold. These adaptations include reduced metabolic rates and molecules called glycopeptides in their body fluids. These molecules act like antifreeze by keeping body fluids liquid at temperatures below freezing. The emperor penguins, the largest, are the only species that depend on the ice for breeding and rearing their chicks.
Penguins feed on krill and fish.
In turn, they are preyed upon by leopard seals and killer whales. Seals Four species of seals inhabit the Antarctic. Weddell seals feed on squid and fish. Crabeater seals feed on krill . They may be the largest group of all seals in the world and probably consume more krill than whales do.