When the harsh Alaskan winter sets in, Arctic squirrels burrow deep into the ground to begin an eight-month hibernation period. They only emerge again in the spring, hungry and eager to reproduce.
Scientists have discovered, however, a new and surprising consequence of climate change: as temperatures increase, females of this species have gradually advanced the date of return to the surface, now 10 days earlier than 25 years ago.
+ Middle East countries in conflict lack funds to combat global warming
On the other hand, males are not ending their deep sleep earlier, which could soon bring problems to the reproduction process of these creatures, according to an article published this Thursday (25) in the journal Science.
Previously, males ended hibernation a month earlier than females, allowing enough time for their testicles, which shrink each autumn, to regenerate and descend in an annual cycle of puberty. But that gap is shrinking.
“If this continues, we expect to start seeing females emerging ready to mate with males before those males are actually fully mature for reproduction,” one of the authors, Cory Williams, a biologist at Colorado State University, told AFP.
– Unique adaptations –
Like many arctic animals, arctic squirrels have developed unique adaptations for extreme winter weather.
They hibernate for about eight months a year, in holes approximately one meter deep in the sandy riverbanks, just above the permafrost of the tundra.
During this time, their body temperature drops from around 37°C to nearly -3°C, the lowest in any mammal, dramatically slowing their brain, lung, heart and other organ functions, in a state called “torpor”.
The team behind the study used long-term data on air and ground temperatures from two locations and from 199 squirrels over the same period.
A significant increase in ambient temperature was detected, as expected for a region known to be warming four times the global average due to climate change.
“We also observed a change in the soil freezing and thawing cycle. Now the ground is freezing later and thawing earlier,” added Williams.
This had two effects on the animals. Even though they went into hibernation at the same time, the time when their core body temperature dropped below 0°C was delayed, which in turn pushed back the date when they need to generate heat to prevent tissue death during torpor. .
And females ended hibernation earlier, accompanying the early spring thaw.
Exactly why this second effect only affects females is unconfirmed, but researchers have theories.
In males, rising levels of testosterone as they prepare to reproduce appear to force the end of hibernation at a fixed point, while females appear to be more sensitive to environmental conditions.
– Cascading impacts –
The advantage of this reduced hibernation is that females come back with more mass and can start gathering resources sooner – which can result in healthier clutches and better survival rates.
On the other hand, they are exposed to predators for longer, in addition to the imminent change in sexual interactions.
There could also be cascading impacts down the food chain, if squirrel predators adapt to the early availability of prey.
It is too early to say what the overall impacts could be.
What’s impressive is the concrete evidence that climate directly affects an ecosystem in a relatively short period of time, said lead author Helen Chmura, a researcher at the US Department of Agriculture’s Forest Service.
“We have a 25-year dataset, which is a very long time frame for science, but a short time frame in terms of ecology,” she told AFP.
#Warming #Arctic #harm #squirrel #reproduction