As Alaskan permafrost warms, hibernating arctic ground squirrels generate less heat, causing females to emerge from hibernation up to 10 days before their male counterparts – a mismatch that could have large, cascading ecological impacts. While reduced thermogenesis due to warming temperatures could allow the squirrels to conserve energy and, thus, increase winter survival, a shortened hibernation season could also increase the exposure of the animals to hungry predators, altering mortality rates, particularly for earlier emerging female squirrels. The phenological mismatch between the sexes may also disrupt reproductive rates. And over longer time scales, continued warming in the Arctic may lead to changes in male squirrel seasonal behaviors, say the authors.