Melting ice: polar bears adapt their diet (and it's not good news)

©Hans-Jurgen Mager via Unsplash

The ice pack around the Svalbard Islands is gradually disappearing, and polar bears (Ursus maritimus) are 'reacting': they're changing their diet to survive, and turning more and more to terrestrial resources. Their behavior, in reality, is nothing more than a further confirmation of rising temperatures.

"This is a surprising discovery," explains Jon Aars, first author of the study, led by the Norwegian Polar Institute. "If we had been asked 25 years ago what the consequences would be of polar bears spending two months less on the ice each year, we would have expected leaner animals, reduced reproduction and the start of a population decline. Instead, we're finding that they're in better condition."

The finding dovetails with another recent study by the University of East Anglia, according to which certain genes in polar bears living in southeast Greenland behave differently in the face of rising temperatures: some of the genes linked to heat stress, aging and metabolism may be 'reacting' to adapt to warmer climatic conditions.

The latest study focused on mapping the physical condition of polar bears, particularly in spring between 1995 and 2019, by measuring the amount of fat the animals had accumulated (using the Body Condition Index, BCI).

The most likely explanation? Polar bears are more able to compensate for the reduced time spent on pack ice by exploiting terrestrial resources. They catch more reindeer, feed on walrus carcasses, eggs, birds and harbor seals.

The latter three species have considerably increased in number during this period, and their availability, unlike that of marine resources, has prompted polar bears to change their diet in order to survive.

A shifting balance

These resources have enabled the bears to maintain, and even improve, their physical condition, even though they spend much more time on land than before.

This phenomenon differs, however, from what has been observed in several other regions of the Arctic, where polar bears become, on the contrary, leaner during years when ice-free seasons are prolonged. Above all, it indicates that the balance is shifting on the Svalbard Islands, and this is not good news.

It also highlights the growing influence of polar bears on terrestrial ecosystems, particularly on bird colonies. As a result, they occupy a greater place in Svalbard's terrestrial ecosystem.

And unfortunately, the phenomenon of dietary adaptability does not mean that the polar bears are saved: in the long term, in fact, it is still likely that their physical condition will deteriorate as the ice continues to melt.

"Polar bears depend on pack ice for a minimum period each year, but we still don't know where this critical threshold lies," stresses Jon Aars.

The physical condition of the animals is considered an early warning indicator, and changes in this area could be among the first signs of more serious consequences in the future. Monitoring data such as that analyzed in this study is therefore extremely important for global management.

The study was published in Scientific Reports.

Sources: Norwegian Polar Institute / Scientific Reports

(©GreenMe.it 2026/Managing editor: Selma Keshkire - The Press Junction/Picture: Hans-Jurgen Mager via Unsplash)