The strange animals that control their body heat
Similarly, in response to an accidental flood in the laboratory, researchers observed a highly unusual, days-long period of torpor in a golden-spined mouse, with its temperature reaching a minimum of about 75°F (24°C).
This more flexible use of torpor may help heterotherms wait out a catastrophe, Geiser says. In contrast, homeothermic species cannot simply reduce their food and water requirements and may not be able to survive harsh conditions.
“Maybe there’s no food, maybe no water, maybe it’s really hot,” says ecophysiologist Julia Nowack of Liverpool John Moores University in England, co-author of the sugar glider study. Torpor, especially in the tropics, has “many different triggers.”
Threats of another type, such as the presence of predators, can also encourage retreat. The (perhaps perfectly named) edible dormouse, for example, sometimes enters long periods of torpor in early summer. At first, this behavior intrigued researchers: why sleep in summer, when temperatures are comfortable and food is plentiful, especially if it meant giving up the chance to reproduce?
After reviewing years of data collected by various scientists, two researchers concluded that because spring and early summer are particularly active times for owls, these little snacking creatures likely chose to spend their nights numb, safely hidden in underground burrows, to avoid becoming dinner. In what is considered a similar strategy for avoiding nocturnal predators, Fjelldal’s bats slightly alter their use of torpor depending on the phase of the moon, spending more time numb as the moon fills and becoming easier to spot.
The fat-tailed dunnart, a carnivorous mouse-like marsupial native to Australia, is the third species to hide when it feels more at risk of being eaten. In one study, researchers placed dunnarts in two types of enclosures: some had heavy plant cover in the form of plastic sheeting, simulating an environment protected from predators, while others had little cover, simulating a greater risk of predation. In higher risk contexts, animals fed less and their body temperatures became more variable.
