Did You Know That Some Primates Build Nests?

A nest is a habitat or shelter that is built by animals to provide protection for themselves and their offspring. Nests can be found all over the world in locations ranging from treetops to the surface of the ground. Animals utilize a variety of objects to build their nests, including grass, leaves, rocks, wood, and even plastics and paper scraps. Nests and nest-building are most commonly are associated with bird species. However, other animal species are also known to take part in this unique behavior. This article highlights some of the primate species that build nests.

What Is a Primate?

The term primate refers to an order of mammal species, which is divided into two suborders: strepsirrhines and haplorhines. These two suborders include a diverse range of animals, such as lemurs, monkeys, apes, lorisids, galagos, and tarsiers. Primates are diverse in size, ranging from as small as a human thumb to over 400 pounds. Typically, primates inhabit tropical areas around the world and can be found living on three continents: the Americas, Asia, and Africa. Not all primates are considered nest builders.

Nest Building Primates

In only one of the previously mentioned primate suborders are all of the species considered nest builders: strepsirrhines. In the haplorhines suborder, only hominid apes have been recorded taking part in this behavior. Both of these primate groups build nests for sleeping, whether during the day or at night. However, only the strepsirrhines species build nests to take care of their offspring.

Strepsirrhines and Nests

Strepsirrhine species include lemurs and lorisoids. These animals build nests in a number of locations, including holes found in tree trunks. For this primate subgroup, nest building is not a learned activity, but rather an instinct. Strepsirrhine nests are used for sleeping and as a safe place to leave young while mothers are out searching for food. In some species, like the mouse lemur and the giant mouse lemur, nests are lined with leaves as a way of controlling the body temperature of offspring. In some cases, as seen with the ruffed lemur, nests are even lined with fur.

Researchers have also found male mouse lemurs occupying nests with multiple females at a time, particularly during mating season. This behavior is also seen in dwarf galagos. Adult lesser bushbabies tend to utilize holes in trees, using only leaves as a way of hiding their young when they must leave the nest in search of food. Aye-ayes, which also belong to the strepsirrhine suborder, exhibit particularly unique nest-building behavior. This species may build hundreds of nests in a short time span, relining them with leaves and other organic matter, and even moving into unoccupied nests at times.

Hominid Apes and Nests

Hominid apes are unique in that they do not build nests based on instinct alone. Instead, this is a learned behavior that is passed on from parents to offspring. The number of nests in a particular area is a crucial piece of data for researchers, as it helps them to determine the species population size. Some researchers even suggest that finding nests is easier than finding an actual primate species. Three types of apes are associated with nest building: chimpanzees, orangutans, and gorillas.

Chimpanzees build nests either up in trees, which are typically used during the night, or closer to the ground, for shorter naps during the day. However, chimpanzees in the Bili forest of the Congo region build their primary nighttime sleeping nests on the ground. In general, chimpanzees search for strong tree branches to build the frame and then fill in the rest of the nest with smaller branches, which are lined with leaves and twigs to create a softer sleeping surface. In one study, researchers discovered that 73.6% of the Ugandan chimpanzees studied specifically utilize the Ugandan ironwood tree to create nest frames. This tree makes up less than 10% of the trees in the forest, indicating that chimpanzees have identified a preference for the strongest material available to them. Having a strong frame is essential for chimpanzee nests, as it prevents this species from falling out of trees while sleeping.

Orangutans learn to build nests when they are just six months old. This species builds its nests where two sturdy branches come together, forming a triangular point up in the treetops. These branches are used as the nest frame and additional nearby branches approximately one inch in diameter are woven together between these original branches to form a sleeping platform. An interesting thing about orangutan nests is that the majority of these branches are bent rather than broken. This means that the tree is not damaged during the nest making process.

Gorillas are more likely to build their nighttime nests on the ground than the other ape species. Only females and juvenile gorillas tend to build nighttime nests in treetops, particularly in areas with a large population of predators. Unlike orangutans, gorillas are at least three years old before learning to build nests. Before this age, young gorillas share nests with their mothers. Gorilla nests are typically between one and five feet in diameter.

Nest Building and Evolution

Researchers have identified a link between nest building and human evolution. Nest building behavior in primates dates back more than 10 million years. Researchers believe that ancient primates began building nests in response to their increasing size. As the primates grew larger, sleeping on a simple tree branch was no longer a viable, safe, or comfortable option. Having safe and comfortable places for sleeping allowed primates and early human species to achieve deeper levels of sleep. This deep sleep, known as non-rapid eye movement (NREM) is a requirement for higher levels of cognitive ability. Some researchers argue that when the ancestors of modern-day humans began to sleep on the ground instead of in trees, they were able to achieve this deep sleep on a more regular basis. Over time, these more comfortable sleeping arrangements led to higher cognitive ability, and eventually brain development.