Tama Zoo houses 22 Chimpanzee. Chimpanzee live in groups, and both males and females have a hierarchy (dominance) within the group. The male who is most dominant in the male hierarchy is called the "first-rank male" or "alpha male."

Currently, the alpha male is "Kenta." One of the important roles of the alpha male is to maintain order in the group, for example, by mediating fights between females. To mediate, he must distinguish between the aggressor and the victim and side with the victim. If he makes a mistake in this regard, the victim will not be satisfied and may chase after Kenta along with other females who are on her side.

Meanwhile, there is also a hierarchy among the 14 adult females. This one is quite complex. The two top females are Peach and Nana. Both Peach and Nana are large and have a physique similar to males, but Peach in particular is very good at winning over males, which is why she maintains her high position in the hierarchy.

Lately, I've often seen Peach and Nana grooming each other and standing side-by-side, putting pressure on other animals. It's not simply that they're good friends; I think they're forming an alliance to protect their respective positions.

Conversely, the lowest-ranking females are Sazae and Marina. Sazae is an individual who often stays alone, seemingly wanting to avoid getting involved in the other's conflicts. Marina is very competitive and has a reckless personality, even going up against those higher in rank than herself. However, she seems to be bad at making allies, and since no one comes to her aid when she picks a fight, she is often seen losing and running away with a tearful face.

The hierarchy among females is difficult to determine because it fluctuates depending on various factors such as whether or not they are in estrus and whether or not they have allies. However, if you focus on a few individuals and observe them carefully, you will gradually begin to see their relationships.

Photo: Nana (right) and Peach, the two leading females.

[Sayoko Tama Zoo, Tama Zoological Park]

(June 1, 2012)