Habitat loss is changing polar bear health

Retreating sea-ice is altering the gut bacteria of polar bears, according to a study by Cardiff University and the United States Geological Survey.

Since the beginning of the 21st century, habitat loss has driven a divide in the southern Beaufort Sea polar bear subpopulation. While ‘offshore’ bears remain on the ice, ‘onshore’ bears migrate to coastal open-water regions.

Researchers analysed over 100 faecal samples to understand how this change in behaviour has impacted the bacterial composition of the different bears’ guts.

“We discovered that diversity and composition are significantly different in onshore bears compared to those that remain on the sea-ice year-round, showing for the first time that global change-driven alterations in habitat use are associated with changes in the gut,” explains Sophie Watson, from Cardiff University’s School of Biosciences.

The effect of this bacterial shift on the long-term health of the onshore bears is still unclear, but it could be a cause for concern.

“The bears that have onshore behaviour are exposed to a greater diversity of parasites (because of their much more varied diet) than the offshore bears, and a change in microbiota could leave them vulnerable to acquiring those parasites,” says co-author Sarah Perkins.

However, she warns that even a shift in preexisting microbes could be detrimental to the bears’ health. “Some microbes within the gut microbiota, if they are able to proliferate, can switch from being commensal to pathogenic.”