A recent study has quantified the substantial amount of carrion left behind by polar bears in the Arctic, establishing its role as a significant food source for various scavenger species. The research details how this biomass, primarily from seals consumed by polar bears, supports a broader Arctic food web and outlines potential ecological impacts should polar bear populations decline.
Carrion Contribution and Scavenger Access
The Arctic is home to an estimated 26,000 polar bears, which primarily consume seals, typically killing one every three to five days. According to the study, each polar bear leaves approximately 300 kilograms of biomass annually. This results in an estimated total of over seven million kilograms of abandoned seal remains across the Arctic each year. A minimum of one-third of a seal carcass is typically left for scavengers.
This carrion provides a food source for numerous Arctic species. Documented scavengers include Arctic foxes, gulls, ravens, other polar bears, snowy owls, wolves, and grizzly bears. Field observations indicate that birds and Arctic foxes are primary scavengers, with foxes often following polar bears. Other polar bears are also known to scavenge from seal kills.
Polar bears generally bring their seal kills onto the ice, making the carrion accessible to terrestrial and avian scavengers. This accessibility is crucial, as many scavengers would otherwise be unable to obtain carcasses from the water. The carrion also functions as a buffer for scavengers during periods of food scarcity.
Research Methodology and Funding
The findings were published in the journal Oikos in October by an international research team led by Andrew Derocher, a professor at the University of Alberta. The San Diego Zoo Wildlife Alliance provided funding for the study and has committed an additional $100,000 per year for three years to support further research.
To quantify polar bear seal consumption rates and the caloric value of seal blubber, Derocher's team analyzed observational and anecdotal scavenging data dating back to the 1930s.
Ecological Implications of Population Changes
The study highlights that a decline in polar bear populations, potentially linked to climate change, could have implications beyond seal numbers, affecting the broader scavenger ecosystem. In regions experiencing polar bear population decreases, an estimated 323,000 kilograms of carrion are lost annually. Additionally, as climate change contributes to ice melt, the accessibility of these food resources on the ice could become more challenging for some scavenger species.