Adult male 'Siberut': Don’t underestimate the hunting abilities of older males! (photo by Maja Gaspersic)
I spent most of the day following a small party of males, including Diouf, K.L., Siberut, Bilbo, Karamoko and the female Tumbo. It was a fairly normal morning until, at about 9:00a.m., I saw that Siberut had captured a juvenile vervet monkey! Out of only 3 observed monkey-hunting bouts, Siberut has been responsible for two – one of these was filmed by a National Geographic photographer (Kris Eckstrom) last summer. Siberut is an older male – I’d estimate in his late 20s or in his 30s; he has no upper incisors whatsoever, although his canines still come in handy for meat eating. I didn’t see how Siberut caught the monkey, although last summer he just ran it down as it leapt from a tree. This time, most of the monkey’s head was already eaten, which is typically how Fongoli chimps eat other primates (from the head down). What’s interesting to me is that I have not heard vervets give alarm-calls to chimps in these situations. Vervets are known to use a specific type of alarm-call for terrestrial predators, such as leopards or dogs (if they are predators of vervets in certain areas). They also use a specific alarm call for snakes and another for avian predators, as well as what we call a “strange human chutter” for unfamiliar humans (at Fongoli, they give the “leopard-alarm call” or terrestrial predator call to humans too, as some groups of people in this area hunt them). Rather than give any type of alarm-call for chimps, at least for chimps that are in close proximity, vervets here appear to remain quiet and employ crypticity as an anti-predator strategy. I interpret this as being an example of the drawbacks of alarm-calling (although in regards to other predators they obviously seem to benefit not only individual vervets but the group as well) when the predator is one that would use those alarm calls to locate prey and more often than not, successfully acquire them. Given their climbing abilities, chimps are more adept predators of vervets than leopards or other terrestrial predators, it would seem.
Anyway, back to Siberut and his monkey. Meat sharing is seen across chimp communities, and Fongoli is no exception. There is, however, what I refer to as “respect” for a hunter and his or her capture. Even though Siberut was surrounded by four males that were higher-ranking than him, only one attempted to coerce Siberut into giving him a piece of meat (this was Diouf, who swayed bipedally at Siberut, made as if to grab a piece of meat but was denied by Siberut; Diouf ranks about 4 or 5 in the dominance hierarchy, while Siberut ranks 10th out of 11). There was some sharing, however; some of it reluctant. Tumbo, the female, and K.L., 3rd-ranking male, as well as Karamoko (9th-ranking male) were especially persistent about “begging” from Siberut. This particular type of begging consists merely of sitting as close as one can to him and staring intently at the meat. Siberut allowed Tumbo to take a couple of pieces of meat from his hand. Some ‘chimpologists’ have interpreted this sort of behavior as “meat for sex”, but Tumbo was not in estrus, although they might make the argument that this was “meat for the prospects of future sex”. I think it is more complicated than that, although I don’t rule it out entirely. As you’ll see below, the highest ranking male (K.L.) did also get some meat (“meat in order to appease high ranking male”?) but so did another low-ranking male (Karamoko), while two middle ranking males (Diouf & Bilbo) got access only to the discarded carcass.
At any rate, Siberut moved away from the other chimps at least a half a dozen times as he ate “his monkey”, and initially both K.L. and Karamoko ate only scraps of meat that he had dropped. K.L. was finally allowed to take 2 pieces of meat from Siberut’s hand, and he was then given one arm of the monkey. Siberut attempted to give Tumbo the other arm, but K.L. takes it from her. Bilbo (ranking about 5th or 6th) approaches Siberut, who fear screams (while still eating monkey, which makes for a very garbled fear scream) and moves away; K.L. follows Siberut and reassures him by repeatedly touching his scrotum. Bilbo doesn’t get any meat. Tumbo is given some entrails and other bits – I can’t really make it out. Finally, Karamoko is given a small piece of meat from Siberut’s hand. It was about this time that Diouf made his aggressive move for some meat but was denied (although he ranks at least 5 places above Siberut in the hierarchy). I see that K.L. mixes his meat with twigs, which is not uncommon – leaves are usually eaten alternately with meat as well. I call this ‘steak and salad’. At 9:37a.m., Bilbo finally gets the tail of the monkey, after Siberut has his fill and drops the carcass. Diouf and Bo (adolescent male who did beg as well but got nothing) are the only ones who did not apparently get any meat. Both examine the last of the carcass but leave it. I went to examine it and found it to be only the skin and part of the tail nearest the base. I would have left it too. The whole “meal” took about 40 minutes, and the rest of the day was pretty calm comparatively! The chimps rested for about 5 hours during the middle of the day, which will only lengthen as the weather gets even hotter toward the latter part of the dry season, and finally made their way to Tukantaba to drink (from a ‘well’ they dug in the stream bottom) and, finally, to nest.