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Word of the Week: Kleptothermy

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Welcome to Word of the Week! This week you will be learning about how some animals stay warm. We are going to dive into the term Kleptothermy! Stay tuned for a new word each Wednesday to amp up your nature vocabulary!  We want to make sure your nature vocabulary is always growing!

What Does Kleptothermy Mean? 

Kleptothermy [KLEP-toh-thur-mee] (noun): Any form of thermoregulation by which an animal shares or steals the body heat of another animal. It may or may not be reciprocal, and can occur in both endotherms 1 and ectotherms 2.

What is Kleptothermy? 

Remember when you were a kid, sometimes teachers may have made you go outside to play even if the weather was cold. To help you stay warm, you may have huddled with your friends, hoping your body’s internal temperature would not make you feel colder. Or when you are older and have a partner you may huddle with them on cold nights to help you get warmer. 

In the animal kingdom, animals perform a similar process and it is known as kleptothermy. It is when animals will share or steal body heat from another animal. How animals share or borrow body heat can be seen in a few ways. 

Sharing Habitat

For example, an animal that steals body heat is the sea krait. When this snake is not in an underground nest, they have a body temperature of around 31 degrees, which is pretty warm for an ectotherm. However, when the sea krait is coiled up inside the sea bird nest its internal temperature becomes more stable and is around 37 degrees. When these birds were not at home the temperature of the nest dropped to 27 degrees. 

Of course, the snake isn’t the only reptile that will take body heat. Many other reptiles from lizards to crocodiles have been known to shelter in the homes of animals that have warm bodies. 

A great example of this is the tuataras, a reptile that looks like a lizard. These reptiles face heating problems just like sea snakes. Researchers have found that tuataras like their internal temperature to be between 19 degrees to 22 degrees. 

However, when the temperature of the forest drops at night, basking in the sun the next day to achieve this preferred internal temperature can take a while. So they will seek the nest of birds at night. Many will use the nest of the fairy prions, and those that did have a high internal temperature thanks to the warm air in the burrows. 


There are some animals that will huddle together to increase or have a more constant body temperature. For example, some species of lizards and snakes such as the boa constrictors and tiger snakes will increase their effective mass by clustering tightly together.

By doing this heat loss is reduced, and their body temperature is conserved and more gradually released. Other species such as bats and birds will share their body heat, especially amongst their young. 

White-backed mousebirds, when in their rest phase will have an internal body temperature of above 32 degrees even when the air temperature was as low as -3 degrees. When these birds come together as a clutter this body temperature is matched with everyone in the group! 

Emperor penguins will huddle together to save energy, to have a high body temperature, and keep their breed fast in the Antarctic winter. This huddling behaviour raises the surrounding temperature the penguins are exposed to above zero. These temperatures can rise up to 37 degrees which are close to a bird’s body temperature. 

Pre-Hatching Life

You might think that thermoregulation processes such as kleptothermy are only needed after an egg is hatched. However, research has shown that this is not the case! When looking into the eggs of the Chinese softshell turtle, researchers were able to find heat differential in the tiny underdeveloped eggs. Movement within the embryos allowed them to maximize the heat they got from their surroundings, increasing their body temperature.

This leads to different development stages of the embryos and how long they need to be incubated. This can help the embryos because a warmer incubation can mean the hatching process is accelerated. 

Kleptothermic Organisms in High Park

This time of year, a great example of non-reciprocal kleptothermy (heat-stealing) is happening in High Park with Garter Snakes. Garter snakes have really complex systems of pheromonal communication.

They can find other snakes by following the pheromone-scented trails that they leave behind. Male and female skin pheromones are very different from each other to be immediately distinguishable. 

However, male garter snakes sometimes produce both male and female pheromones. During the mating season, this ability tricks other males into attempting to mate with them, which causes the transfer of heat in kleptothermy. 

This is an important advantage immediately after hibernation because it enables more activity. Male snakes giving off both male and female pheromones have been shown to have more copulations than normal males.

How great it is to learn the different forms of kleptothermy used by various animals! Just as humans will huddle together sometimes to share body heat, animals do it too! On your next spring visit to High Park, watch for Garter Snakes slithering around in the savannah and forest!

At the High Park Nature Centre, we want to help become more aware of different animals and their homes! Through our programs, guided nature walks and even our blog, we are here to help you stay aware and connected to nature!

  1. Also referred to as warm-blooded; Endotherms are animals that maintain a constant body temperature independent of the environment.
  2. Also referred to as cold-blooded; Ectotherms are animals whose regulation of body temperature depends on external sources