Friday, May 1, 2015

Aliens Invading North Territory

There are a lot of differences between male and female hyenas. From size (females being larger) to aggressiveness, rank and more, the sexes are very distinct. One more distinction between males and females is what happens after the age of reproductive maturity. Females will remain in their natal clan at this point and take advantage of mating opportunities with immigrant males who came from other clans. Natal males, on the other hand, will disperse from their natal clan and find a new clan to live in during the years after reaching reproductive maturity. Dispersal around this age is not specific to hyenas, but happens in many mammals. It is, among other things, a mechanism to avoid inter-breeding and an attempt to increase a male’s chances at getting mating opportunities. Males and females both inherit their mother’s rank in their natal clan when they are born. If natal males happen to be high ranking, this is helpful in situations like carcass sessions because it helps them get more food. When a male hyena disperses and joins a new clan, he is automatically the lowest ranking hyena in the clan until another new male joins after him. This means that all immigrant males are lower ranking than all natal males. Even though this is the case, natal males almost never get mating opportunities, since rank plays very little role for males in how often they get to mate. So, even though they will lose their rank in the clan and become the lowest ranking hyena in their new clan, they must disperse.

            One of the most important parts of our job here is to be able to keep track of, and reliably ID hyenas so that we can make sense of their interactions and monitor any changes in the hierarchy. Male dispersal can make this a little bit more tricky. Pretty often, we will have hyenas that we have never seen before coming through our territories. In order to keep track of them, after confirming that they aren’t already named from one of our other study clans, we give them an alien number and keep track of their interactions with hyenas that are already members of the clan that they are visiting. If they’re seen interacting with hyenas in the clan three times, then they officially become a member of the clan. At this point we give them a real name; immigrant males are named after cities.

            Just this week we had the pleasure of welcoming a new immigrant into our North study clan. Meet Castine, formerly known as AL1037:

            Male hyenas will often visit many clans before they decide to settle in one, which is why they become an alien before they become an immigrant male in our books. Because of this, its rare that we gain a new immigrant male in one of our clans, so this was an exciting week. Best of luck, Castine, I hope the other North hyenas give you a warm welcome!

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