Kleptothermy

Some animals share heat to stay warm.

They can huddle close together. This helps them keep a steady body heat.

Penguins do this in the cold snow. It helps them save their energy.

Other animals find heat in different ways. Some snakes live in holes made by birds. The birds keep the hole warm. This helps the snakes stay warm too.

Even tiny eggs can feel heat. Small turtle babies move to find warm spots. This helps them grow well. Sharing heat is a smart way to live.

Some animals use the heat from others to stay warm. This is called kleptothermy. It is a way to keep a steady body temperature.

Many animals use huddling to share heat. Bats cluster together to stay warm.

Emperor penguins also huddle in the cold. This helps them save energy during the winter.

Inside the group, it can get very warm. It can reach 37.5 °C.

Other animals find heat in different spots. Some lizards and snakes live in burrows made by birds. The birds keep the holes warm. This helps the reptiles stay warm too.

Even tiny turtle embryos can find heat. They are still inside their eggs. They move to find warm spots. This helps them grow. Moving to cooler spots can also keep them safe. This shows that even tiny babies can control their own heat.

Some animals stay warm by using the heat from others. This is called kleptothermy. It is a special way of managing body temperature. Animals can share heat through a process called huddling. This happens when many individuals cluster tightly together. Huddling helps them keep a steady temperature. It also helps them save energy.

There are a few ways this works in nature. Some animals are endotherms, which means they make their own body heat. Others are ectotherms, which means they rely on the outside world for warmth. Kleptothermy can happen between these different types. For example, a lizard might live in a burrow made by a mammal. The mammal's heat keeps the burrow warm for the lizard. This helps the lizard stay at a higher temperature.

Scientists have studied many different animals to see how they do this. They looked at how emperor penguins survive the cold Antarctic winter. These birds huddle together in large groups. The air around them can jump from -17 °C to over 20 °C. Inside the huddle, it can even reach 37.5 °C. This warmth helps them stay healthy while they raise their chicks.

Other animals use clever tricks to get heat. Male Canadian red sided garter snakes use a trick called female mimicry. They make fake scents to attract other males. These rival males then cover the first snake in a big group. This transfers heat to the snake that used the trick. This heat helps them wake up faster after hibernation. In the ocean, blue-lipped sea kraits also use bird burrows. These reptiles stay much warmer in bird nests than in other places.

Even tiny babies use heat before they are born. Researchers studied embryos of Chinese softshell turtles inside their eggs. These tiny embryos can feel changes in temperature. They move around to find the warmest spots in the egg. This helps them grow faster and hatch sooner. Moving to cooler spots can also protect them from danger. It shows that even the smallest living things can manage their own environment.

Kleptothermy is a biological process used for thermoregulation. Thermoregulation is how an animal manages its body temperature. In kleptothermy, an animal shares the metabolic thermogenesis of another animal. Metabolic thermogenesis is the heat produced by an animal's own body processes. This behavior allows animals to maintain higher and more stable body temperatures. It can happen between animals of the same species or different species. It can also occur between endotherms and ectotherms. Endotherms, like birds and mammals, produce their own internal heat. Ectotherms, like many reptiles, rely on external sources for warmth.

For kleptothermy to work, two major conditions must be met. First, there must be thermal heterogeneity in the environment. This means there are different temperature zones available. A warm organism must create these zones in a cool area. Second, another animal must use these temperature differences. By moving into warmer spots, the animal increases its thermal inertia. Thermal inertia is the ability to resist changes in temperature. This process helps animals retard heat loss. It also reduces the metabolic expenditure needed to stay warm.

One common method of kleptothermy is huddling. In huddling, many individuals cluster tightly together to share heat. This is common among gregarious endotherms, which are social animals. For example, bats cluster together to maintain stable temperatures. Emperor penguins also use huddling to survive the Antarctic winter. In a tight penguin huddle, the ambient temperature can rise significantly. While the external air might be -17 °C, the huddle can reach 20 °C. It can even reach 37.5 °C, which is close to a bird's body temperature. This allows them to save energy while breeding.

Kleptothermy can also involve habitat sharing between different species. Many ectotherms exploit the heat produced by endotherms by using their shelters. For instance, lizards and snakes may use mammal burrows for warmth. Termites create mounds that maintain high, constant temperatures. These mounds are used by various lizards, snakes, and crocodilians. The blue-lipped sea krait is a specific example of this. These reptiles live in burrows used by wedge-tailed shearwaters. This association raises the sea krait's body temperature compared to other habitats. It also makes their body temperature more stable.

Some animals even use clever, non-reciprocal tricks to steal heat. This is sometimes called heat-stealing because the warmth is not shared back. Male Canadian red-sided garter snakes use female mimicry. They produce fake pheromones, which are chemical signals, after hibernation. Rival males mistake these signals and attempt to mate with the mimic. This causes the rival males to cover the mimic in a large group. This mass of males transfers heat to the mimic. This heat allows the mimicking snake to become revitalized quickly. This gives them an advantage when they try to mate.

Even life before hatching involves thermoregulation. Research on Chinese softshell turtle embryos shows they are not passive. These tiny embryos can detect thermal differentials, or temperature differences, inside the egg. They move to exploit small-scale heat variations. This movement helps them maximize heat gain from their surroundings. A warmer incubation can increase the rate of embryonic development. This can lead to a faster hatching process. Faster hatching may minimize the time an embryo is at risk from predators. It also helps embryos avoid lethal thermal extremes by moving to cooler areas.

The evolution of these behaviors is linked to how animals manage energy. Endothermy evolved in vertebrates along separate, parallel lines. It is linked to the selection for high levels of aerobic metabolism. This allows for high muscular power and sustained activity. However, endothermy is energetically very expensive. It requires much more food than ectothermic life. Ectotherms often evolve to be thermal generalists. This means they can function across a wider range of temperatures. In contrast, endotherms often evolve narrow performance breadths. They use precise thermoregulation to specialize in specific tasks.