Lecture: Grooming: Narrator: Listen to part of a lecture in a biology class. Professor: Today we're going to continue our discussion of grooming habits among primates. Before we talk about this study you were assigned to read, let's review the concept of grooming. At our last class, we discussed auto-grooming and allo-grooming. Auto-grooming is the term used when animals clean their own fur – feathers, scales and so on. Animals must remove dirt, insects, dead skin, parasites to ensure good hygiene, prevent disease. Allo-grooming, on the other hand, involves animals grooming each other. Not only will they remove the dirt and insects, they'll also do things like scratch and massage each other. But there's another purpose of allo-grooming that's been well known for quite some time. And It's not to just keep your friends' fur clean, is it? It's a communication tool. When animals groom each other, they bond, build trust. Studies have shown this sort of grooming releases endorphans into the blood. Endorphans are chemicals that reduce pain sensations and bring on feelings of relaxation. So allo-grooming reduces group tension and helps to resolve conflicts or avoid conflicts all together. Basically, it strengthens the social structure of the group, and that's its main purpose for chimpanzees, probably more important than hygiene. But your reading assignment was a study investigating yet another role that allo-grooming plays in chimps. Um ... in the past, researchers have suggested that allo-grooming is also used by males to establish and maintain dominance. But there haven't been any studies confirming this. So let's talk about the alpha male chimpanzees in the study. A chimpanzee community is hierarchical with the alpha male having the highest rank. Now, there is only one alpha male in a chimpanzee community, and all the other chimps are below him in rank. No one is dominant to the alpha male. The alpha male gets his choice of food and mating partners. Now, typically among animals, it's the biggest, most aggressive male in the group who becomes the alpha. But what does the chimp study say? Who can briefly summarize it? Yes, Andrew. Andrew: It was a ten years study of a group of chimps living at a national park in Africa. And what it involved was, well, the researchers studied three different chimpanzees. Each was the alpha male of the group at a different time over the ten years, the researchers wanted to know how each male reached the top of the hierarchy and how they stayed there. Anyway, the three chimps ranged in size, so there was one that was really big and aggressive. Another one was in the middle, and one that was the smallest of the three. Professor: That's exactly right. And what were the grooming patterns? These three alpha males demonstrated. Someone else? Female Student: Okay. Well, the three had grooming patterns. The smallest alpha male, he groomed others obsessively, of the three, he groomed the most. Then there was the medium sized alpha male, sometimes he used his size and aggression to dominate and he also groomed other chimpanzees just not to the extent the smallest alpha male did. The biggest male like Andrew said he was really aggressive. He used his size and physical attacks to become the alpha male. He was groomed by the other chimpanzees, but that's basically it. So he just used his size. Professor: Right. For the largest chimp, size and aggression were his only strategies, and they seem sufficient. So based on observations of these three alpha males, it seems that grooming is used as a kind of alternative tactic for gaining dominance in the community. The medium and the smaller sized alpha males needed something besides their size to help gain the support of the community. The medium size chimpanzee engaged in some grooming and the smallest chimpanzee, well, I guess he had to work the hardest. He engaged in excessive grooming as a way to calm down rivals and build bonds within the community. So this study, It's the first time we've been able to provide support for the idea that grooming is used as a strategy to achieve status by alpha males. Now, we need to keep in mind that the study only focused on the grooming behavior of three alpha male chimps. Not exactly a huge sample size, but you know, it's certainly a welcome addition to the existing work on the dynamics within a chimpanzee community. And other researchers in the field who want to continue exploring this topic should consult this study.