A two-week leap in breeding: Antarctic penguins' striking climate adaptation

A decade-long study led by Penguin Watch, at the University of Oxford and Oxford Brookes University, has uncovered a record shift in the breeding season of Antarctic penguins, likely in response to climate change.

These changes threaten to disrupt penguins’ access to food and increase interspecies competition. The results have been published (20 January—World Penguin Awareness Day) in the Journal of Animal Ecology.

Lead author Dr. Ignacio Juarez Martínez (University of Oxford/Oxford Brookes University) said, “Our results indicate that there will likely be ‘winners and losers of climate change’ for these penguin species.

“Specifically, the increasingly subpolar conditions of the Antarctic Peninsula likely favor generalists like Gentoos at the expense of polar specialists like the krill-specialist Chinstraps and the ice-specialist Adélies. Penguins play a key role in Antarctic food chains, and losing penguin diversity increases the risk of broad ecosystem collapse.”

The researchers examined changes in the timing of penguin breeding between 2012 and 2022, specifically their “settlement” at the colony, the first date at which penguins continuously occupied a nesting zone.

The three species of penguins studied were the Adélie (Pygoscelis adeliae), Chinstrap (P. antarcticus) and Gentoo (P. papua), with colony sizes ranging from a dozen to up to hundreds of thousands of nests. They used evidence from 77 time-lapse cameras overlooking 37 colonies in Antarctica and some sub-Antarctic islands, which ensures conclusions are relevant to species as a whole and not just specific populations.

The results demonstrate that the timing of the breeding season for all three species advanced at record rates. Gentoo penguins showed the greatest change, with an average advance of 13 days per decade (up to 24 days in some colonies).

This represents the fastest change in phenology recorded in any bird—and possibly any vertebrate—to date. Adélie and Chinstrap penguins also advanced their breeding by an average of 10 days.

Senior author Professor Tom Hart (Oxford Brookes University and founder of Penguin Watch) said, “Ecologists are good at counting populations to show trends, but often the early warnings of decline can be found in the behavioral change of animals, which can be very hard to monitor.

“The idea of this whole monitoring network is to put something in place that does both; monitoring populations and their behavioral responses to threats. This study proves the benefits of monitoring animals at a landscape level.”

These record shifts are happening in relation to changes in the environment including sea ice, productivity and temperature. Each monitoring camera was equipped with a thermometer, enabling researchers to also track the temperature changes at colonies.

The data reveal that colony locations are warming up four times faster (0.3 ºC/year) than the Antarctic average (0.07 ºC/year), making them one of the fastest-warming habitats on Earth.

Though statistical models suggest that temperature appears to be one of the dominant drivers of the observed shifts in breeding season, it remains unclear whether the changes reflect an adaptive response or not, risking a potential mismatch with other ecological factors such as prey availability.

Even in the best-case scenario, it is unclear how much more elasticity these species will be capable of displaying if temperatures keep rising at the current rate.

Co-author Dr. Fiona Jones (University of Oxford) added, “As penguins are considered ‘a bellwether of climate change,” the results of this study have implications for species across the planet. Further monitoring is needed to understand whether this record advance in the breeding seasons of these penguin species is impacting their breeding success.”

This research was also made possible thanks to international collaborators in the UK (University of Oxford, Oxford Brookes University, British Antarctic Survey), the US (Stony Brook University, NOAA) and Argentina (CADIC-CONICET).