This is the first time fish have been seen actively becoming torpid—a state similar to hibernation in land animals—as part of an annual cycle. “A lot of freshwater fish go [unexpectedly] dormant in winter because a drop in temperature lowers their metabolism,” said study co-author Hamish Campbell, a zoologist at the University of Queensland, Australia.

“By contrast, these Antarctic fish actively reduce their ‘cost of living,'” he said… “The fish became 20 times less active in winter compared to summer,”… About every week or so the cod wake up and swim around for a few hours, the team observed. “This is quite similar to ‘denning’ in bears, where the hibernation isn’t so deep and the animals can be disturbed, then spend some time awake before going back to bed,” Fraser said.