Wednesday, February 13, 2008

Big day at the cave!

February 10, 2008.

Today was an exciting day with the chimps because the young female Tumbo was in estrus, so a large party was in attendance. In addition to 8 adult males, a number of other females, along with their offspring joined the group. This is typical when a female is in estrus - it is a very social event, no matter who you are!

It was almost comical to watch 8 adult males keep an eye on Tumbo's every move - and to change their own travel trajectories to match hers! Meanwhile, Tumbo nonchalantly continues on her way, stopping frequently to eat (as is typical for her - I swear she eats more than any chimp I know!), seemingly without a care in the world for these 8 guys following her around. She does pay them a bit of attention at times, if you get my drift, but I wanted to write today about something else the males were very interested in.

One thing that makes the Fongoli chimps unique, compared to chimpanzee communities that have been studied elsewhere, is that they use caves for resting, feeding and socializing during the hottest times of the year - when these caves are cooler than the surrounding environments. Some of thes caves are more like rock shelters. There are also what we call 'dirt caves', which have been carved out by animals, under the banks of streambeds in the area.

Today, the large party (of about 27 individuals) set off for one of these small, dirt caves, which was located along the Kerouani stream. All of the streams are dry by this time of year. Diouf seemed to lead the way, and throughout the afternoon, as various tussles between males ensued, Diouf always seemed to remain near the cave and would jump back in first chance he got after a minimal amount of participation in a fight or two.

The highest-ranking male in the party, Yopogon (see photo here, taken by Maja Gaspersic Cisse in Dec. 2007), who is actually 2nd-highest ranking male behind Foudouko (who we haven't seen in over a month) didn't seem to be able to bully anyone out of the cave so that he could go in. Dominance interactions over females in estrus are much more indicative of the male dominance hierarchy than are interactions by males over food or space.

In this case, the chimps were eating soil from this particular cave (we call it 'geophagy'). Chimps at all long-term study sites have been observed to exhibit this behavior. Gorillas are better known for the behavior, and other primates exhibit it extensively as well - colobus monkeys, for example. It appears to provide some minerals to the diet, but in colobus monkeys, similar behavior (charcoal eating) also seems to detoxify some of the plants they consume.

In addition to being very much interested in eating soil (which was really hard for me to imagine - the temperatures were well into the 90's, and as far as I know, this chimp party did not drink on this day. I can't imagine how they did it - it made my mouth dry to think about it!), the males were interested in being able to lounge in the cave as well. Being a small cave, only about 3 males could fit comfortably in it. This caused more of a ruckus than having access to Tumbo did (although, granted, she is not quite at that stage of her estrous period where she is most 'attractive' to males)!

Yopogon proceeded to display at length up, over and around the cave in an attempt to supplant one of the other - lower-ranking! - males from it. This just wasn't working. They ignored his attempts, often reassuring one another as he stamped by. Finally, he appeared to take his frustrations out on Bilbo, who was not actually in the cave at the time but who was one of the first males to go in and eat. Bilbo did not take kindly to Yopogon's threats - I couldn't actually see if he slapped him, but it sounded like he did. A chase ensued and, as it frequently does, ended up high in the trees.

With Bilbo screaming in rage initially, and Yopogon finally screaming in fear, the rest of the party let loose with VERY loud WRAAAAHH barks, which are given during such aggression. You might think of them as being something along the lines of, "Stop it! Cut it out! Things have gotten out of hand!". They REALLY got upset as Bilbo and Yopogon actually grappled high in the trees, about 15 meters (45 feet, I believe) off the ground. At this point, I was standing in the midst of the hollering group, trying to see exactly what was going on.

The next thing I knew, Yopogon had grabbed a limb that would not support his weight, in an effort to elude Bilbo. The limb tore from the tree, and Yopogon plummeted about 12 meters (about 35 feet) to the ground!!! You can imagine the uproar!

At this point, I was afraid that what had probably happened to Mamadou (see post below) would be what I would then see with Yopogon.

Fortunately, he doesn't seem to have been seriously hurt and, actually, the fight continued along the ground for some time - over a hill and out of my sight.

Yopogon finally made his way back to the cave. When I turned back to look there immediately after the fall, I saw that a few females had taken advantage of the situation and had run inside to grab some clay. Diouf, who also didn't stray far from the cave, swaggered a little and chased them back, and went back to dozing and eating there for another couple of hours. Yopogon groomed with various males, trying to make up for the hurt feelings, etc., that had come out of all the aggression. I finally saw that he got as close as being able to lie at the lip of the cave. A very exciting day for me but one that is fairly typical for chimps - especially when you have a community, like Fongoli, that is characterized by so many adult males. All's well that ends well, I suppose...

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