Spring is here, and love songs are playing! But... do animals mate for reproduction?

"One day of floating life is one lifetime of mayflies." On this day, mayflies mate crazily and then die. Cephalopod deep-sea squids will float up in groups during the breeding season, mate, use up their energy, leave behind egg sacs and die. These animals mate with their lives, and the purpose of mating is only to reproduce. In contrast, human sexual intercourse is more romantic. In addition to reproduction, it is also endowed with deeper cultural connotations, such as performing the Zhougong ritual and going to Wushan to make love. In fact, as close relatives of humans, primates are also the same.

Part 1

Tibetan macaques: Sex is a way to build friendships

I once went on a business trip to Sichuan to investigate the number and distribution of golden snub-nosed monkeys and Tibetan macaques. I saw a group of Tibetan macaques mating in the Baishuihe National Nature Reserve. Their movements were very brief and did not depend on the occasion. Seeing this scene, I thought of a question: Do monkeys mate for reproduction? If so, why do they mate all year round? If not, what is the purpose of mating?

Tibetan macaque

Source: Wikipedia

Tibetan macaques (Macaca thibetana) fall somewhere between seasonal and non-seasonal reproduction: they can mate in all seasons, but give birth only between January and August, which fully demonstrates that mating is not always for reproduction.

In the world of Tibetan macaques, mating is not only a way to achieve the purpose of reproduction, but also a way to establish friendship. This is because Tibetan macaques live in evergreen broad-leaved forests, where there is less food available, which results in a situation of "many monkeys and little food" (the spatial configuration between individuals in the group is relatively dense), and the survival competition pressure between individuals is high. Mating can alleviate the competition pressure. This situation is like Wenzhou in the past, where there were many people and little land, so there were business groups.

In a monkey group, the monkey king does not have enough power to possess all the female monkeys. Here, female monkeys have the right to choose their mates. Interestingly, according to Xiong Chengpei's observation: pregnant female Tibetan macaques tend to mate with high-ranking male monkeys, while non-pregnant female monkeys mainly choose low-ranking male monkeys to mate. Why is this?

Pregnant female monkeys mainly choose high-ranking male monkeys because they establish a friendly relationship with the stronger male monkeys in the group through mating activities to reduce their own competitive pressure, which is equivalent to finding a backer for themselves. However, non-pregnant female monkeys mainly choose low-ranking male monkeys to mate. This choice of female monkeys is puzzling (scientifically not fully understood). But one thing is clear: female monkeys have the freedom of sexual choice, which can make the population genetically diverse.

In addition, high-ranking male monkeys and low-ranking female monkeys participate in mating more often than low-ranking male monkeys and high-ranking female monkeys. What does this mean? To make an analogy, the chances of a rich boy and a poor girl being together are greater than the chances of a poor boy and a rich girl being together.

Although female monkeys have the right to choose, they will also face sexual disturbance. In layman's terms, sexual disturbance is when two monkeys are mating and another monkey comes to interfere. This behavior mostly occurs when the mating male monkey begins to mount the female monkey. According to Xiong Chengpei's observation, low-ranking monkeys rarely disturb the mating of high-ranking monkeys, while high-ranking male monkeys can easily interrupt the mating of low-ranking monkeys.

Take the example of "White Haired Girl". Xier, a peasant girl, and Dachun, a peasant boy, fell in love and planned to get married in autumn. However, the landlord Huang Shiren fell in love with Xier and easily separated Xier and Dachun. Here, Huang Shiren is a high-ranking landlord, while Xier and Dachun are low-ranking peasants.

Not only do adult monkeys love to mate, but young monkeys also enjoy it. These young male monkeys have no chance to practice with real weapons, so they mate with each other. In the eyes of humans, this is homosexuality, but in fact, it is normal among non-human primates. Young monkeys simulate mating to prepare for the future. Some monkeys, without the cooperation of other monkeys and without wives, solve the problem by themselves. Similarly, it is not uncommon for male monkeys in the monkey group to masturbate.

Part 2

Bonobos: Make love, not war

Bonobos (Pan paniscus) are one of the two species of chimpanzees. They were originally thought to be the same species as chimpanzees. It was not until 1920 that the difference between the two was discovered and they were classified as a separate species. Bonobos have short black fur on their bodies, usually with a white spot on their buttocks, a gray-brown face, gray hands and feet covered with sparse black hair. Males are 73-83 cm long, and females are 70-76 cm long. Males weigh 40-45 kg, and females weigh 30 kg.

Bonobos

Source: VEER Gallery

Bonobos are highly promiscuous animals. They mate more frequently than other primates, from heterosexual to homosexual. Moreover, they do not have a specific breeding season. They mate all year round, either mating or on the way to mating. Therefore, bonobos were once considered the most promiscuous animals in the animal world. However, on the other hand, we have to admit that bonobos are the animals most similar to humans in terms of sex life. In addition to humans, they are the only animals that adopt a face-to-face mating posture and French kiss at the same time.

Why are bonobos so "lustful"?

In the society of bonobos, sex is not only for reproduction, but also has other functions. They use sex to greet each other, apologize and ask for extra food. For females in the bonobo group, in addition to their own children, they will have sex with any other of their kind. They will masturbate and masturbate each other. This frequent mating is believed to be a way to consolidate social bonds and eliminate conflicts. When resolving disputes, bonobos do not use violence, but use sex. Therefore, sex does not only exist between opposite sexes, but also between the same sex. Therefore, it is no exaggeration to say that the entire community of bonobos is built on sex.

Homosexuality is well documented in about 500 species of animals, suggesting that sexual orientation is innate. But African bonobos seem to be homosexual simply because they love peace. Almost all peaceful animals are bisexual, and they often resolve conflicts based on the principle of "make love, not war." They have sex frequently, make calls without restraint, and have same-sex sex frequently. About two-thirds of same-sex sex occurs between female bonobos.

Bonobos

Source: VEER Gallery

In daily life, bonobos spend almost all their time in trees, where they build simple nests, forage for fruit on branches, and walk on the ground with slightly bent lower limbs. They have a certain range of activities, with an area of ​​26-78 square kilometers, and the foraging area is often where they gather.

Like hospitable humans, different groups of bonobos often interact with each other. They maintain a long-term mother-child relationship, and even if they are in different groups, children often return to the group to visit their mothers. Bonobos have the habit of taking a nap at noon, and can distinguish different colors and make 32 different calls. Their behavior and social behavior are more similar to humans, which is of great significance in anthropological research.

Part 3

Japanese macaques: mating with deer

Of course, there are even more bizarre mating patterns. Not long ago, Japanese primate experts observed that female Japanese macaques in central Japan actually had sex with sika deer. We know that monkeys are playful, so maybe they were just having fun on the backs of their long-legged neighbors? How do we define this as a sexual behavior?

Japanese Macaque

Source: Veer Gallery

When female macaques mate with male monkeys, they will actively invite them to mate, lift their buttocks and invite them to mate with the male monkeys (to mate with each other). Noëlle Gunst-Leca of the University of Lethbridge witnessed this process in 2014: young female macaques invited deer to mate in the same way, and spent a lot of time maintaining physical contact with the deer. The female monkeys will ride on the deer and push its pelvis. During mating, female macaques will also take the initiative to groom the deer, using their fingers to pick out secreted particles or some parasites on the skin.

Researchers believe the practice is sexual in nature and believe it could be the start of a new social trend: Young female macaques, known for their same-sex sexual intercourse with males, gradually realize that adult male sika deer can provide them with sexual release.

Not all deer are willing to have sex with female monkeys. The researchers found that female macaques and male deer had a much higher chance of success than female deer and juvenile male deer. Of the 13 successful cases, only one interaction between a female macaque and an adult male deer failed. Of the eight failed interactions, five occurred on either the female or the juvenile male, and the female macaques who mounted were thrown to the ground.

Why is this so? This has to start with the social structure of macaques. Macaques are a polyamorous society, with a female ratio of about 3:1 in a monkey group, with more females than males. In a monkey group, high-ranking male monkeys do not like young female monkeys because they lack reproductive experience, and even the first fetus from mating often has difficulty surviving. Therefore, young female monkeys will simulate mating with each other, firstly to gain sexual experience, and secondly to obtain some kind of sexual release. Japanese macaques often live with deer, and they are familiar with each other. Many times, monkeys will ride on deer to play. It is very likely based on this that suddenly one day a young female monkey discovered that she could get sexual satisfaction by mating with a deer, and then spread it in the group. Because monkeys themselves are very good at learning.

Produced by: Science Popularization China

Author: Zhao Xumao, Institute of Zoology, Chinese Academy of Sciences

Producer: Computer Network Information Center, Chinese Academy of Sciences

This article only represents the author's views and does not represent the position of China Science Expo

This article was first published in China Science Expo (kepubolan)

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