Key information
- Polar bears in the Chukchi Sea have shown, over a thirty-year period, an increased risk of contracting diseases previously unknown to them.
- The five pathogens that have become more common in polar bears are the parasites that cause toxoplasmosis and neosporosis, the bacteria that cause rabbit fever and brucellosis, and the canine distemper virus.
- Changes in pathogen exposure among polar bears serve as indicators of broader ecological changes affecting other species in the Arctic ecosystem.
Blood samples taken from polar bears in the Chukchi Sea over a thirty-year period reveal an alarming trend: an increased risk of contracting previously rare diseases among these Arctic inhabitants. Researchers analyzed blood samples taken between 1987 and 1994, then a second set of samples taken between 2008 and 2017. The results indicated a significantly higher prevalence of chemical markers indicating infection by viruses, bacteria or parasites in the most recent samples.
Although it is difficult to determine the precise impact on bears’ physical health from blood samples alone, wildlife biologist Dr. Karyn Rode of the U.S. Geological Survey noted that this evolution reflects broader changes within the Arctic ecosystem. The study focused on six specific pathogens, namely viruses, bacteria and parasites typically associated with land animals, but occasionally found in marine species, including those hunted by polar bears.
Pathogens found in polar bears
Dr. Rode notes that the study period coincided with a substantial loss of sea ice and an increase in land use for this particular population of polar bears. This prompted researchers to examine whether exposure to these pathogens had changed, particularly those considered more prevalent on land. The five pathogens that have become more common in polar bears include two parasites that cause toxoplasmosis and neosporosis, two types of bacteria that cause rabbit fever and brucellosis, and the distemper virus.
Implications of the study
Despite their resistance to disease, Dr. Rode emphasizes that these results highlight the transformations underway in the Arctic. Polar bears are listed as an endangered species in the United States, with the main threat to their survival being the continued loss of sea ice habitat – their essential hunting platform for marine prey.
Previous research using photo collars on polar bears has shown that when they spend more time on land due to reduced sea ice, they have difficulty getting enough calories. Dr. Rode explained that as apex predators, polar bears contract these pathogens primarily through their prey. Therefore, observed changes in pathogen exposure in polar bears serve as indicators of broader ecological changes affecting other species within the Arctic ecosystem.
