page_title: Kleptothermy
section_title: Huddling
hierarchical_section_title: Kleptothermy / Huddling
caption_attribution_description: English: Typical Indiana bat cluster during hibernation before White-nose Syndrome was discovered and confirmed in an abandoned limestone mine on the Wayne National Forest in Lawrence County, Ohio. Note the presence of a banded bat at the far left. Credit: Tim Krynak
context_page_description: Kleptothermy is any form of thermoregulation by which an animal shares in the metabolic thermogenesis of another animal. It may or may not be reciprocal, and occurs in both endotherms and ectotherms. One of its forms is huddling. However, kleptothermy can happen between different species that share the same habitat, and can also happen in pre-hatching life where embryos are able to detect thermal changes in the environment.
  This process requires two major conditions: the thermal heterogeneity created by the presence of a warm organism in a cool environment in addition to the use of that heterogeneity by another animal to maintain body temperatures at higher levels than would be possible elsewhere in the local area. The purpose of this behaviour is to enable these groups to increase its thermal inertia, retard heat loss and/or reduce the per capita metabolic expenditure needed to maintain stable body temperatures.
  Kleptothermy is seen in cases where ectotherms regulate their own temperatures and exploit the high and constant body temperatures exhibited by endothermic species.
context_section_description: Huddling confers higher and more constant body temperatures than solitary resting. Some species of ectotherms including lizards and snakes, such as boa constrictors and tiger snakes,  increase their effective mass by clustering tightly together. It is also widespread amongst gregarious endotherms such as bats and birds (such as the mousebird and emperor penguin) where  it allows the sharing of body heat, particularly among juveniles.
  In white-backed mousebirds (Colius colius), individuals maintain rest-phase body temperature above 32 °C despite air temperatures as low as -3.4 °C. This rest-phase body temperature was synchronized among individuals that cluster. Sometimes, kleptothermy is not reciprocal and might be accurately described as heat-stealing. For example, some male Canadian red sided garter snakes engage in female mimicry in which they produce fake pheromones after emerging from hibernation. This causes rival males to cover them in a mistaken attempt to mate, and so transfer heat to them. In turn, those males that mimic females become rapidly revitalized after hibernation (which depends upon raising their body temperature), giving them an advantage in their own attempts to mate.
  On the other hand, huddling is the key that allows emperor penguins (Aptenodytes forsteri) to save energy, maintain a high body temperature and sustain their breeding fast during the Antarctic winter. This huddling behaviour is the key that raises the ambient temperature that these penguins are exposed to above 0 °C (at average external temperatures of -17 °C). As a consequence of tight huddles, ambient temperatures can be above 20 °C and can increase up to 37.5 °C, close to birds' body temperature. Therefore, this complex social behaviour is what enables all breeders to get an equal and normal access to an environment which allows them to save energy and successfully incubate their eggs during the Antarctic winter.
caption: Bat cluster together to maintain high and constant body temperatures.
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