Male Arctic ground squirrels go through puberty every year. As if that wasn’t difficult enough, the females now also have a problem.
According to an article published Thursday in the journal Science, climate change appears to be causing them to come out of hibernation earlier. That’s important, because it can disrupt the timing of the animals’ mating cycle.
Usually, males emerge from hibernation earlier than females to prepare for the spring mating season. They need time each year to become sexually mature again because their testosterone levels drop sharply in the winter.
Then the females wake up. But scientists have found that as temperatures rise, female ground squirrels emerge up to 10 days earlier than they used to. Researchers think it has to do with earlier thawing of the ground.
The hibernation pattern of the males, meanwhile, does not seem to change.
“This study suggests that males and females of the same species may respond differently to climate change,” said Helen E. Chmura, a research ecologist with the United States Forest Service and lead author of the paper. “This could have important implications for reproduction.”
The squirrels’ problems are part of a much larger crisis. Wildlife around the world is struggling. On land, the main cause is humans taking over too much of the planet and erasing the biodiversity that was there before. Overfishing is the biggest problem in the oceans. Climate change makes survival even more difficult.
For now, Arctic ground squirrels are still plentiful in the wild. The International Union for Conservation of Nature classifies them as a species of least concern, meaning they are not threatened or in need of protection. But the paper says the new hibernation mismatch “has the potential to affect their chances of survival.”
Any decline in the squirrel population can disrupt the local food web. Nearly all Arctic predators, from wolves to eagles, rely on them as a food source.
Although the Arctic is warming faster than any other region on Earth, relatively little research has been done on the effects of this warming on animals. This new paper, spanning more than 25 years in northern Alaska, is one of the first long-term research projects to provide strong evidence that warming directly alters the physiological processes of arctic species.
“This study is relatively unusual because it shows that warming has a direct impact on a mammal,” said Cory T. Williams, an assistant professor at Colorado State University and a co-author of the study. “Some people might say, ‘Okay, a 10-day down payment over 25 years doesn’t seem that fast.’ But in terms of climate, that is incredibly fast.”
Arctic ground squirrels may look cute, but males can be very territorial. They get into a lot of fights during the mating season, some of them deadly. They have tails, but not long, bushy ones like squirrels found further south. And they make distinctive whistling sounds that could easily be mistaken for the chirping of a small bird. Some Alaska Natives call them parka squirrels because their fur forms a nice, warm fringe for the hood of a jacket.
Scientists have long been interested in their hibernation patterns.
During the long hibernation, the squirrels’ body temperature can drop to about 27 degrees Fahrenheit, or about minus 3 degrees Celsius, with their resting heart rate dropping to just three beats per minute. More knowledge about that process could lead to advances in therapeutic hypothermia, a medical treatment that lowers body temperature to prevent injury. It is sometimes used after cardiac arrest.
But the most pressing challenge, scientists say, is getting to grips with the changes taking place in the far north.
“The big gap is just understanding what’s happening in the Arctic in general,” said Dr. Williams. “This study shows why we need long-term projects to understand the changes at different levels.”