Rana sylvatica isn’t even the only frog to go into suspended animation. Other species living in desert environments, like Spencer's burrowing frog from central Australia, will go dormant and bake themselves in the heat. They can spend months encased in a mucous cocoon, patiently waiting for the rains to bring them back to life. Some fish, like the African lungfish, use a very similar strategy during droughts.

Compared to frog popsicles and frog jerky, the seasonal hibernation of ground squirrels and other small mammals seems subtle and painless. They cosy up in dens and tree hollows, munching on food caches, and go for occasional walks to stretch their legs. While they keep breathing and don’t freeze, a hibernating ground squirrel still produces so little heat that it is cold to the touch.

Many other animals, including some not particularly renowned for surviving extreme environments, will go into a deep sleep state known as daily torpor, a less severe form of metabolic depression. Hummingbirds, for example, slip into torpor to bed down for the night. They cut their body temperature by half, and drop their heart rate from about 1200 beats per minute to fewer than 200. Still, hummingbirds seem to just scrape by most of the time, burning through huge amounts of fat and losing about 10% of their body weight per night. It’s no wonder that they wake up so very hungry.

Whether they are amphibians, mammals, birds, or something else, animals use metabolic depression to thrive in places where they otherwise have no business surviving. At northern latitudes, frozen ponds, streams, and lakes leave frogs with nothing to eat and nowhere to live during the winter. Similarly, small mammals have a difficult time finding food when most nuts and fruits are buried under inches of snow. For the hummingbird, daily torpor is the only way their life in the fast lane happens at all – they use so many calories just to stay alive that they must drastically reduce their metabolism to take a nap without starving to death.