Beyond being large predators and, when necessary, functioning as nutrient recyclers by feeding on carcasses, polar bears (Ursus maritimus) are also important providers of food for other necrophagous species that live in the Arctic.
A study, published in the journal ‘Oikos’, reveals that these large white bears leave behind about 7.6 million tonnes of food every year. Thus, scientists say that polar bears create vital food sources that help support a wide network of scavenger species in the icy worlds of the far north of the Earth.
The research team says that, as a result, polar bears act as a “crucial link” between marine and terrestrial ecosystems. How? By hunting, for example, seals in the ocean and by leaving their carcasses on the ice, bears are transferring large amounts of energy from one habitat to another and making food accessible to other animals.
The study reveals that, at least, 11 other vertebrate species benefit from this service provided by polar bears, such as Arctic foxes (Vulpes lagopus), common ravens (Corvus corax) and wolverines (Gulo gulo).
“Our findings quantify, for the first time, the enormous importance of polar bears as providers of food for other species,” says, in a press release, Holly Gamblin, from the University of Manitoba (Canada) and the first author of the article.
The scientist notes that one of the things that stands out most in this work is the fact that there are no other species that hunt in the same way as polar bears, capturing prey at sea and dragging them onto the ice, leaving afterwards a substantial amount of food within reach of other species.
The Arctic is warming at least twice as fast as the global average and threatens the survival of many animals, including polar bears, as the loss of sea ice is making access to offshore marine zones, where their favorite prey, the seals, reside, more difficult. Without these floating icy platforms, bears have neither where to rest nor to hoist their prey.
On the other hand, this study stresses that the disappearance of polar bears will not only affect the species itself but also other species that have learned to take advantage of the leftovers left by the great bears.
Fewer bears will mean less food left within reach of other species, which may also end up suffering population losses, with all the ecological consequences that may follow. Therefore, the authors of this study say that protecting polar bears is not only about conserving that species, but also all the others that depend on them.
