Gentoo penguin. Image by LoneWombatMedia from Pixabay

Human influence has changed what gentoo penguins eat

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Human activity has changed the diets of gentoo and chinstrap penguins over the past century, according to US research. In the 1930s and 1960s, both penguin species were able to eat their fill of krill as whalers and sealers kept the numbers of larger krill-eating mammals down. But in the latter half of the century, gentoo penguins shifted to eating fish and squid as whale and seal numbers bounced back. Chinstrap penguins were less lucky - during this time, their population dwindled as they continued to feed exclusively on krill.

Journal/conference: PNAS

DOI: 10.1073/pnas.1913093116/-/DCSupplemental

Organisation/s: Louisiana State University, USA

Funder: This work was funded by US National Science Foundation Office of Polar Programs, and the Antarctic Science Bursary.

Media Release

From: PNAS

Penguin responses to climate change and human activity

A study examines the response of penguin species to past human exploitation and recent climate change in Antarctica. Krill is a main food source for Antarctic penguins. However, the historic harvesting of whales and seals in addition to recent anthropogenic climate change are thought to have led to shifts in krill abundance over the past century. To better understand the ecological implications of these changes, Michael J. Polito and colleagues examined the diets of chinstrap and gentoo penguins in the Antarctic Peninsula by analyzing the nitrogen stable isotope values of amino acids in feathers from the 1930s, 1960s, 1980s, and 2010s. The authors found that both species had low trophic positions and primarily fed on krill during krill surpluses in the 1930s and 1960s caused by harvesting of krill-eating marine mammals. In contrast, during the latter half of the past century, gentoo penguins advanced a full trophic position and showed an adaptive shift from strictly eating krill to including fish and squid in their diets. Chinstrap penguins, however, continued to feed exclusively on krill. During the same time period, chinstrap penguins experienced severe population declines in the Antarctic Peninsula, whereas gentoo penguin populations increased. The findings suggest that species with specialized diets are more sensitive to human-induced environmental change than generalist foragers, according to the authors.

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