Polar bears face mounting challenges in a changing, warming world, mostly related to their waning wintery wonderland habitats. But they may be increasingly infected with germs and parasites, too.
Compared to a few decades ago, polar bears living near Alaska are now more frequently exposed to five different pathogens, researchers report October 23 in PLOS ONE.
“With warming, it just allows pathogens to persist in environments they couldn’t persist in before,” says Karyn Rode, a wildlife biologist at the U.S. Geological Survey’s Alaska Science Center in Anchorage.
But these changes are poorly understood in the Arctic, a region that is morphing rapidly under climate change (SN: 11/15/21). Rode and her colleagues looked to polar bear immune systems for crucial insights.
The Chukchi Sea polar bear population was a perfect fit. These bears, native to the waters between Alaska and Russia, have experienced dramatic losses of sea ice habitat, leading many to spend long periods on land in the summertime. There, they are exposed to humans and their garbage, which are possible sources of pathogens. The Chukchi bears also range farther south than many other polar bears’ populations.
“If there are pathogens moving northward into the range of polar bears, then [the Chukchi Sea] would be a place we would expect to detect that,” Rode says.
The researchers screened blood serum and fecal samples collected from 232 Chukchi bears from 2008 to 2017 for the presence of antibodies against a suite of bacteria, viruses and parasites. If a sample has antibodies aimed at fighting a specific pathogen, it suggests the bear’s immune system has encountered the pathogen at some point. The team then compared that analysis to a similar one of 115 bears from 1987 to 1994.
The proportion of polar bears…
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