USGS
In a warming Arctic, polar bears are spending more time on land
As the Arctic warms, polar bears face an increasing risk of contracting viruses, bacteria, and parasites that they were less likely to encounter just 30 years ago, research has shown.
A study examining blood samples from bears in the Chukchi Sea – between Alaska and Russia – has provided insight into how polar bear disease could be linked to ice loss.
Researchers analyzed samples collected between 1987 and 1994, as well as samples taken three decades later – between 2008 and 2017.
The study revealed that a significantly higher number of recent blood samples showed signs of bears being infected with one of five viruses, bacteria, or parasites.
USGS
Wildlife biologist Karyn Rode (pictured with a sedated wild polar bear) and her team collected blood samples from wild bears to monitor the health of the animals.
It is challenging to determine the physical health effects on the bears from blood samples, but wildlife biologist Dr. Karyn Rode from the US Geological Survey noted that it indicated a changing trend in the entire Arctic ecosystem.
The researchers tested for a total of six different pathogens – viruses, bacteria, or parasites primarily associated with land-based animals but previously found in marine animals, including those that polar bears prey on.
The study spanned three decades, during which there was a significant loss of sea ice and increased land use in this population of polar bears,” Dr. Rode explained.
“So we wanted to investigate if exposure had changed – especially for some of these pathogens that are thought to be primarily land-based.”
The five pathogens that have become more prevalent in polar bears – two parasites causing toxoplasmosis and neosporosis, two bacteria causing rabbit fever and brucellosis, and the virus causing canine distemper – collectively represent disease-causing agents.
“Bears are generally resilient to disease,” Dr. Rode explained. “It typically does not impact bear populations, but it highlights the changing conditions in the Arctic.”
Key polar bear facts
There are approximately 26,000 polar bears remaining worldwide, with the majority in Canada. Populations are also present in the US, Russia, Greenland, and Norway. Polar bears are considered vulnerable to extinction by the International Union for Conservation of Nature, with climate change playing a crucial role in their decline. Adult males can reach lengths of around 3m and weigh close to 600kg. Polar bears can consume up to 45kg of blubber in one meal. These bears have a keen sense of smell and can detect prey from up to 16km away. They are adept swimmers and have been observed up to 100km offshore, swimming at speeds of approximately 10km per hour, partly due to their slightly webbed paws. USGS
Research using collar cameras has unveiled the dietary habits of polar bears during the ice-free summer, as well as capturing unexpected social interactions.
In the US, polar bears are categorized as a threatened species; scientists highlight that the primary threat to their survival is the ongoing loss of sea ice habitat, which serves as a hunting platform for marine prey.
Previous studies utilizing collar cameras on bears have shown that as they spend more time on land throughout the year – in the absence of available sea ice for hunting – the bears struggle to find sufficient calories.
Dr. Rode pointed out that polar bears are top predators: “Our study indicates that they are primarily exposed to certain pathogens through their prey species.
“Therefore, the changes in pathogen exposure for polar bears reflect the changes experienced by other species as well.”
The findings have been published in the scientific journal PLOS One.