These days, no matter where you turn, you'll hear people talking about 'Nong Moo Daeng'—the adorable baby female hippo and the newest member of Khao Kheow Open Zoo. Her cuteness brings smiles to everyone who sees her, and as a psychiatrist, I'm happy to see people feeling joy. Even my patients have shown improvement lately—thanks to following news about Nong Moo Daeng! (We'll talk another day about how animals can positively affect our mental health.)

But there’s something many people might not know: a hippo was one of the reasons I became interested in psychology and eventually chose to become a psychiatrist. That hippo, however, wasn’t Nong Moo Daeng—it was a male baby hippo born at a zoo near my home many years ago (let’s not mention how many years ago, haha).

What I remember clearly about that baby hippo is that it was covered in wounds. When I asked the zoo staff, they said it had been bitten by its own father. The staff explained that the mother gave birth late at night, and since the staff didn’t notice right away, the baby was bitten as soon as it was born. If they had come a bit later, the baby might have been so badly injured it wouldn’t have survived.

But why would the father hippo bite its own baby? Well, that’s actually an instinct in many mammals.

In the wild, when a pregnant mother hippo is about to give birth, she isolates herself in a deep forest. After giving birth, she checks whether the baby is male or female. If it’s female, she’ll bring the baby back to the herd to raise it in a big family. This hippo family can include dozens of members, but what’s interesting is that there’s only one adult male—the 'father' of the group. The rest are the main wife, secondary wives, 'mistress number 3, 4, 5,' and many daughters—like Nong Moo Daeng, who would be the youngest daughter. In a classic Chinese-style big family, we might call her 'Ah-Soy-Mui.' It's basically an all-female household with just one male leader—sounds a bit like a harem, doesn’t it?

Now, if the baby is male, the mother hippo will raise him alone in the forest until he’s weaned. Then she’ll return to the herd, leaving the baby to survive on his own. When he grows up and becomes strong enough, with natural desires to find a partner, he’ll have to go out and search for a female. But all the females are already part of other herds. So he must challenge the dominant male of one of these groups. If he wins, he gets the whole harem. In the wild, this kind of fight happens often