kleptothermy
huddling

Animals also engage in kleptothermy in which they share or even steal each other's body warmth.

This causes the transfer of heat to them in kleptothermy, which is an advantage immediately after hibernation, allowing them to become more active.

Kleptothermy is any form of thermoregulation by which an animal shares in the metabolic thermogenesis of another animal.

Even Morton Feldman found his following, a more diverse one than the usual huddling of specialists.

Again, the ballroom and battle scenes represent a certain huddling of masses, but Mr. Major does not have much choice.

City, Huddling Place, Census, 1944.