Most primates are not known for their hibernation habits—except for the western fat-tailed lemur that hibernates for seven months in a tree hole. But in 2013, scientists discovered two new lemurs in Madagascar that did hibernate— Crossley’s dwarf lemur and the Sibree’s dwarf lemur. Unlike more hibernators that lower their body temperatures and hide in special hidden spots in the cold winter, the western fat-tailed lemurs actually hibernate from the cold and the heat, with temperatures that can reach 85°F (29.4°C) over a long, dry season—when food and water are in short supply.

But the two new lemurs live in the high-altitude forests, where it does go below freezing. The scientists found that although the animals burrow underground and breathe once every several minutes, their temperature does not drop, remaining constant. This may indicate that primates as hibernators are more prevalent than we think.

Pacing is an indication of lack of stimulation. A recent doctoral study found that larger animals, which have a larger home range in the wild, are particularly prone to pacing in captivity, a behavior known as cage stereotypy. Most reputable zoos attempt to assuage pacing by providing what is known as “animal enrichment.” Enrichment may include constantly changing objects, odors, and sounds to mimic the types of stimulations that would be found in the animal’s natural habitat. As an example, in order to keep life interesting for poison dart frogs from South America, keepers will hide their crickets inside a coconut with holes drilled in it. The frogs then have to seek out the food inside the chirping coconut.