How polar bears provide food for other Arctic species

By Stephen Beech

Polar bears act as "crucial" providers of food for other Arctic species, reveals new research.

The iconic mammals - officially classified as "vulnerable" - annually provide millions of kilos of meat, which supports a vast Arctic scavenger network, according to the findings.

The new study, published in the scientific journal Oikos, reveals for the first time the key role polar bears play as carrion providers for other Arctic species.

It is estimated that there are between 22,000 and 31,000 polar bears left in the wild, but man-made climate change and global warming are making life increasingly tough for them.

The research team estimates that polar bears leave behind around 7.6 million kilos (16.7 million lbs) of their prey annually, creating a "massive and vital" food source for a wide network of arctic scavengers.

They say their findings show that the apex predators are a "crucial" link between the marine and terrestrial ecosystems - and protecting them is essential not just for the bears but for other species too.

By hunting seals on the sea ice and abandoning the remains, the researchers explained how polar bears transfer a substantial amount of energy from the ocean to the ice surface, making it accessible to other animals.

Researchers identified at least 11 vertebrate species known to benefit from the meat, including Arctic foxes and ravens, with an additional eight potential scavenger species.

Study lead author Holly Gamblin, of the University of Manitoba in Canada, said: “Our findings quantify for the first time, the sheer scale of polar bears as a food provider to other species and the interconnectedness of their ecosystem.

“What is apparent from this review is that there is no other species that adequately replaces how a polar bear hunts, in which they drag their prey from the water to the sea ice and leave substantial remains for other species to access.”

Previous research has emphasized that continued warming in the Arctic and the resulting loss of sea ice directly endanger polar bear populations.

But the new study highlights that a decline in polar bears would not only impact the species itself but the loss of the carrion they provide could have "significant" consequences for the entire Arctic ecosystem.

Study co-author Dr. Nicholas Pilfold, of San Diego Zoo Wildlife Alliance in the United States, said: "Our research highlights the important role of polar bears as carrion providers.

“The sea ice acts as a platform for many species to access scavenging resources provided by polar bears, and ultimately, declines in sea ice will reduce access to this energy source."

He added: "Our findings indicate that documented declines in polar bear abundance in two subpopulations have already resulted in the loss of more than 300 tonnes of food resources for scavengers annually.”

Dr. Pilfold says the findings highlight the interdependence of arctic wildlife species and their shared vulnerabilities in the face of rapid environmental change.