The Central Arctic caribou herd in Alaska is experiencing a "steep decline" in its population, and scientists are researching the reasons why.
The herd's population peaked at 70,000 members in 2010, but it began to dwindle in 2013, dropping to 50,000 that year. Surveys conducted this year pegs the herd's number at around 22,000. The herd suffered a higher-than-usual death rate among females tracked by radio collars, but like the overall population decline, scientists are at a loss to explain why.
State wildlife biologist Beth Lenart told the Associated Press that she intends to check weather data to see if changes in the weather may have influenced vegetation that the caribou eat to survive. "But other than that, it's pretty challenging," to determine the culprit behind the population drop, Lenart said.
Researchers have already ruled out hunting and animal predators, like bears and wolves, since both potential causes wouldn't result in such sharp declines. Climate change has been ruled out as well due to a lack of evidence. Similarly, caribou sometimes change herds, but the rate at which that happens is unclear, according to Lenart.