A solitary female gibbon suddenly gave birth! Is this a moral decline or a distortion of ape nature?

Not long ago, a bizarre and trying-to-find-the-reason thing happened in a zoo called "Mori Shinkansen" in Sasebo City, Nagasaki Prefecture, Japan: a female white-handed gibbon named Momo suddenly gave birth to a baby.

Momo and his children. Image source: Sen Kirara, Kujukushima Zoo and Botanical Garden, Nagasaki, Japan
What's so strange about gibbons giving birth? The story starts with this type of gibbon -

01

The endangered white-handed gibbon

This is called a white-handed gibbon. They have very interesting looks and their hair colors vary from black to dark brown to light brown. For example, the two in the picture below are white-handed gibbons with light brown and black hair. If you don't know, you might mistake them for two different gibbons.

This type of gibbon is mainly distributed in Southeast Asia, and was originally distributed in Yunnan Province in our country. They feed on fruits and leaves, and occasionally eat some insects or flowers.

Unfortunately, due to hunting by humans and habitat loss caused by road construction and deforestation for farmland development, the number of white-handed gibbons in my country has become extinct in the wild.

In addition, the wild white-handed gibbons take a long time to reach sexual maturity (often starting to reproduce for the first time at the age of 11) and only give birth to one baby at a time, so it is very slow to restore the population. Therefore, they have become an endangered species.

02

Find the baby gibbon's father

In this sense, it is a good thing that Momo, a female white-handed gibbon in the "Senqiluo" Zoo, can give birth to offspring. Why do you say this is a strange thing?

This is indeed a strange thing. Momo's birth caught all the keepers off guard. The reason is simple. Momo is a female white-handed gibbon that is kept alone. Moreover, it has been kept alone for several years. It has no contact with other male white-handed gibbons. How could it be pregnant? Whose child is it?

In order to find out who the father of the little white-handed gibbon is, the zoo collected DNA samples from several other white-handed gibbons in the cage and did a special paternity test. Soon, the University of Tokyo gave the test results, and the father of the little white-handed gibbon was a 34-year-old male white-handed gibbon named "Ito" in the zoo.

The "culprit" Ito. Image source: Sen Sen (森きらら) of the Kujukushima Zoo and Botanical Garden in Nagasaki, Japan

The results of the paternity test came out, and the father of the little white-handed gibbon was also found. But this result did not solve the doubts in the keeper's mind - the zoo deliberately kept Momo alone, in order to prevent Momo from mating with other white-handed gibbons in the zoo and giving birth to offspring. So, how can a female white-handed gibbon raised alone give birth to a child?

Wait, aren’t white-handed gibbons endangered? Why do we need to prevent them from giving birth? That’s a long story…

There is a reason why the zoo does not allow white-handed gibbons to mate. In fact, Ito is Momo's father. If they mate, it will be considered "inbreeding", which may produce offspring with genetic defects. In order to better protect them, the "Mori Kirara" Zoo has taken isolation measures.

So, although Ito and Momo were kept in the same room (the middle room in the picture below), the zoo kept Ito and Momo separately in different cages in the room.

Moreover, the zoo was very careful when arranging the exhibition, and never allowed Ito and Momo to appear in the exhibition hall outside at the same time. In other words, they never had the opportunity to mate and produce offspring. Therefore, even after getting the DNA test results, the director and keepers of the "Mori Kirara" Zoo were still confused.

Until recently, Mori Kirara Zoo finally discovered the reason for this strange thing: Ito and Momo were mating through the gap between the cages. There was an iron door separating Ito and Momo's cages. The iron door was 0.5mm thick and covered with small ventilation holes with a gap of only 9mm.

Although the gap is very small, it may be enough for male white-walled gibbons, whose genitals are very small, about the thickness of a human little finger. Therefore, after excluding other possibilities, the zoo believes that Ito is most likely to mate with Momo through these small holes to produce offspring.

Although Ito and Momo are inbred, fortunately, their offspring are healthy. By February 2023, the baby gibbon has grown to 2 kg and 40 cm tall. Now, it can go to the exhibition hall to play by itself, and it is very active and naughty.

In addition, the Mori Kirara Zoo also plans to let the baby gibbon get familiar with Ito after it is weaned, so that the "family of apes" can live together as soon as possible. Hopefully, the family of three can be reunited soon.

References:

[1]https://www.yomiuri.co.jp/local/kyushu/news/20230201-OYTNT50070/

[2]https://news.yahoo.co.jp/articles/cae9175d341e86ba2b90ce8f05be17bc67afcafd

[3]https://www.yomiuri.co.jp/national/20210402-OYT1T50163/

Author｜Science Scraps

Review | Wang Kang, Director of the Science Museum of the National Botanical Garden