Male arctic ground squirrels go through puberty every year. As if that wasn’t hard enough, now females have the problem too.
Climate change appears to be causing them to emerge from hibernation earlier, according to a paper published Thursday in the journal Science. This matters because it could disrupt the timing of the animals’ mating cycle.
Males usually come out of hibernation earlier than females to prepare for the spring mating season. They need time to reach sexual maturity again each year because their testosterone levels drop sharply during the winter.
Then the female wakes up. But scientists have found that as temperatures rise, female ground squirrels emerge up to 10 days earlier than before. Scientists think this is related to earlier thawing of the soil.
The hibernation mode of the males does not seem to change in the meantime.
“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 who was lead author of the paper. “This could have important implications for reproduction.”
The squirrels’ plight is part of a much bigger crisis. All over the world, wildlife is struggling. On land, the main cause is that humans are taking up too much of the planet and wiping out the biodiversity that was there before. In the oceans, overfishing is a major problem. Climate change makes survival even more difficult.
There are still plenty of arctic ground squirrels 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 conservation efforts. But the paper says the new hibernation mismatch “has the potential to affect their survival probability”.
Any decline in squirrel populations could disrupt the local food web. Almost 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, there is relatively little research on how this warming affects animals. This new paper, covering more than 25 years in northern Alaska, is one of the first long-term research projects to provide strong evidence that warming is directly altering the physiological processes of Arctic species.
“This study is quite unusual because it shows that warming has a direct impact on mammals,” said Cory T. Williams, assistant professor at Colorado State University and co-author of the study. “Some people might say, ‘Okay, a 10-day shift in 25 years doesn’t seem that fast.’ But in terms of climate, it’s incredibly fast.”
Arctic ground squirrels may look cute, but males can be very territorial. During the mating season, they get into many fights, some deadly. They have tails, but not long, bushy ones like squirrels found further south. And they make distinctive squeaking sounds that can easily be mistaken for the chirping of a small bird. Some Alaska Natives call them parka squirrels because their fur makes a nice, warm fringe on the hood of their coat.
Scientists have long been interested in their hibernation patterns.
During their long hibernation, squirrels’ body temperature can drop to about 27 degrees Fahrenheit, or roughly minus 3 Celsius, while their resting heart rate drops to as low as three beats per minute. More knowledge about this process could lead to advances in therapeutic hypothermia, a medical treatment in which the body’s temperature is lowered to prevent injury. It is sometimes used after cardiac arrest.
But the most pressing challenge, scientists say, is to manage the changes taking place in the Far North.
“The big gap is in understanding what’s going on in the Arctic in general,” said Dr. Williams. “This study shows why we need long-term projects to understand changes that occur at different levels.”