Recent studies show a dramatic decline in penguin populations around Antarctica. Especially Chinstrap and Adelie Penguins have declined a lot over the past years (with 4.3% and 2.9% per year respectively). Some scientists predicted an increase in Chinstrap populations as they are a more pelagic species, while Adelies prefer sea ice in the non-breeding season. With the melting sea ice due to climate change there will be more open water which is preferred by Chinstraps. However unfortunately both species are in decline.
Reason for this is a decline in krill, the main dish of almost every Antarctic species. There are three reasons for this decline (not all of them bad). First of all the numbers decline because of the changing climate. Krill feeds on phytoplankton that lives under the sea ice. With the diminishing sea ice, krill has a harder time finding food. Second reason is an increase in krill fishing by humans. The last reason is, strangely enough an increase in whale and fur seal numbers. In the mid 20th century large whales and fur seals were heavily hunted and their numbers dropped dramatically. This resulted in an increase of the krill populations, and thus in more food for other krill eaters. Because of this the Adelie en Chinstrap numbers increased. With the hunt on whales and fur seals now banned, their numbers increase steadily. This means they eat more krill, leaving less food for the penguins…. How the increase in one endangered species can result in the decline of another….