It has become a symbolic image for climate change: a lonely polar bear perches on a small ice floe in the Arctic Sea. Here, the sea ice continues to dwindle, also due to increasing concentrations of greenhouse gases in the atmosphere. And this is a big problem for the animals: they need the sea ice, especially for hunting seals.
But apparently not all polar bears are dependent on the sea ice. A small, newly discovered population in Southeast Grönland uses glacier ice cream for hunting instead, researchers around Kristin Laidre from the University of Washington and the Greenland Institute of Natural Resources report in the specialist magazine »Science«. For the investigation, the team analyzed movement data as well as genetic and demographic information from 36 years.
In southeast Greenland, the sea ice is largely unusable for capturing seals: From about February to the end of March, the polar bears can use the sea ice that is frozen on the coast. For the rest of the year, more than 250 days, the region is free of it – polar bears can "only" fast for up to 180 days. The population newly described by the research team uses the freshwater ice on glacier fronts for hunting the rest of the time.
Glacier ice could thus offer a retreat for some polar bears if the sea ice continues to dwindle, the authors suspect. The main prey of polar bears, the ringed seal, also lives in such habitats of Greenland and Svalbard.
It is unclear whether polar bears can withdraw into habitats on glaciers in the long run. Because these habitats also change. There is also another obstacle, as Elizabeth Peacock from Emory University School of Medicine writes in an accompanying article on the study: the long generation duration of the polar bears, i.e. the time interval between two generations. According to an estimate by the International Union for Conservation of Nature (IUCN), this is 11.5 years. This makes adapting to changed environmental conditions a lengthy process for animals.
