Giant panda brother becomes sister overnight! Why is it so easy to misidentify the gender of a panda?

The "brother" of the giant panda Hehua has become a "sister"! After three and a half years of misidentification of the gender, the giant panda Heye was confirmed to be a girl !

Reports on the Internet about this blunder

In fact, the panda gender misunderstanding incident is not an isolated case. A more famous incident of "mistaking a male for a female" also happened to Hehua and Heye's father Meilan . When Meilan, a "Chinese expatriate in the United States", returned, she launched a grand event to select a son-in-law. As a result, before the ceremony was over, Meilan showed a series of male panda estrus behaviors - she failed to be selected as a son-in-law, but became a son-in-law.

Meilan, the two-year-old giant panda | Wikipedia

How to identify the gender of giant pandas?

Seeing this, you may have a big question: Why is the gender of giant pandas still misidentified? Is it because the gender is difficult to identify?

1

Chromosome identification

This is true, but not true. Since giant pandas are also dioecious, with sex determined by sex chromosomes, and sex reversal does not occur, chromosome identification can certainly accurately determine the sex of an individual. And currently we can use facial swab testing, a non-invasive testing method, to achieve this goal, which is safe and reliable.

2

primary sex characteristics

However, if we do not use technology and use the simplest visual observation method to make judgments, it would be quite difficult to accurately determine the gender of a juvenile giant panda or even the gender of an adult giant panda .

Let's first talk about the most important basis for visually determining sex - primary sexual characteristics, that is, the characteristics of the external genitalia. Like many carnivores, the primary sexual characteristics of giant pandas are not very obvious during infancy . The male testicles need to develop for several months before they move from the abdominal cavity to the scrotum. The scrotum is located relatively close to the ventral side, not hanging behind the buttocks like cats or dogs. In addition, it is obscured by loose abdominal skin and fluffy hair, so it is not very obvious in appearance.

Moreover, compared to their body size, the penis of giant pandas is very short. Even when they are lying on their backs or sitting with their legs spread out, it is difficult to see the exposed part with the naked eye, which makes it very difficult to determine the sex of giant pandas based on their primary sexual characteristics.

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3

Body shape differences

In addition to the difficult-to-distinguish external genitalia, distinguishing the differences in body shape and posture between female and male animals is also a commonly used method for determining gender.

Take bear relatives as an example, the male Asian black bear has a noticeable mane around its neck, the male brown bear has a larger face and a more robust body than the female, these are relatively intuitive differences. However, the difference in appearance and body shape between the female and male giant pandas is not significant, and it is difficult to distinguish them in terms of face shape, body shape or posture .

4

Behavioral characteristics

Therefore, when judging the sex of giant pandas by visual inspection, some behavioral characteristics that are easier to observe are often used as the basis for judgment. For example, male giant pandas will make more climbing movements when playing, and prefer to rub against tree stumps and other places to leave their scent information.

Of course, this method of judging purely by behavioral characteristics will inevitably encounter some "eccentric" "outliers" . For example, the protagonist He Ye in this news has been lively and active since childhood, likes to crawl around, and has shown many behavioral characteristics of male giant pandas, so her gender was misjudged. On the contrary, her father Meilan was treated as a "girl" because he was too quiet when he was young.

However, this kind of mistake usually only happens to young to sub-adult giant pandas. After entering the estrus period, the behavioral characteristics of male and female giant pandas will show more obvious differences. For example, male giant pandas prefer to urinate upside down on tree stumps to show their strength, and they will also have more sniffing behavior. This is why the mistake of mistaking the gender of giant pandas is often discovered when the giant pandas are adults or about to become adults .

Then the question arises: Why don't we seem to care too much about their gender before they reach adulthood? The answer is actually quite obvious: After all, for captive giant pandas, we only consider finding mates for them after they reach adulthood. It would be bad if we match them up with someone else like Meilan did. On the small hand, it would mean that they would not get any fruit from living together for many years, which would lower the overall fertility rate. On the big hand, if two adult giant pandas in estrus were locked together and a fight or bloodshed occurred, it would be a big problem.

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Why are some animals difficult to distinguish between male and female?

In fact, apart from giant pandas, many carnivores and primates do not show overly obvious sexual characteristics when they are young . For example, the testicles of cats only descend into the scrotum as they grow older; the fur color of white-cheeked gibbons will gradually change from grayish yellow to black during development, and then the fur color of female individuals will turn back to golden yellow when they reach sexual maturity. Therefore, it is common that the gender of young animals is difficult to distinguish visually, and it is nothing new.

There is a reasonable reason for hiding sex characteristics. In the life history of many social animals, adult individuals often fight fiercely for territory, status and mating rights, showing strong aggression. And this kind of fighting is often strongly correlated with the sex of the individual.

Therefore, hiding one's sexual characteristics before sexual maturity can, to a certain extent, help reduce the aggression of other individuals of the same species toward oneself . Therefore, in the process of natural selection, those animals whose sexual characteristics are not obvious before sexual maturity have more opportunities to survive in the fight between the same species, grow to maturity and reproduce offspring. As a result of long evolution, the phenomenon of the sexual characteristics of such animals being fully revealed only after sexual maturity and mating conditions are met has been produced.

The above-mentioned animals often show a huge difference in appearance between males and females, which is what we call "sexual dimorphism". It takes a lot of energy for animals to grow and maintain beautiful sexual characteristics, such as flowing manes, gorgeous tail feathers, sky-blue cheeks, etc. Therefore, in addition to declaring gender, showing that male individuals have a healthy and strong body is a sign of being a suitable mating partner, and it is also a weapon used to compete with the same sex for mating rights.

As for animals like giant pandas, which usually live solitary lives and rarely gather in groups during the mating season, it is rare for them to have to compete for mating rights. There is really no need to waste precious energy on body growth and deliberately evolve characteristics that can intuitively declare their gender . Naturally, the difference in appearance between the two sexes will not be so obvious.

If you think about it, our human babies have difficulty distinguishing between boys and girls for the same reason that giant pandas have difficulty distinguishing between males and females, right?

Planning and production

This article is a work of Science Popularization China-Starry Sky Project

Produced by: Science Popularization Department of China Association for Science and Technology

Producer｜China Science and Technology Press Co., Ltd., Beijing Zhongke Xinghe Culture Media Co., Ltd.

Author: Yilang Elang, popular science creator

Review丨Zeng Yan, Senior Engineer, Institute of Zoology, Chinese Academy of Sciences

Planning丨Fu Sijia

Editor: He Tong