east and west side coming together

The following is a description of the three most memorable days since habituation of the east community began almost three years ago. After  leaving the nest site on May 11 the east bonobos started travelling west. Lambert was following the bonobos alone, as his gps batteries died.  He sent a message to camp with his last position and a direction. Just before we left camp we got a second message saying that the group  crossed the Bompusa River, so Nono and I went out on the west side of  the study area. Fourty minutes later we met Lambert on Ndjango trail. He lost the bonobos nearby. We took over and found the group near the river. I was prepared to cross the river back to the east, but instead the group travelled north and later turned west, into the range of the west community. After feeding in a couple of maku trees with plenty of fruits, the east bonobos made their night nests on the west side, 250 meter from the main trail on the west side. The following day the east group fed in the same maku trees and further travelled south. In a dense swamp they found a dead liana. The whole group fed intensively on the wood for over half an hour. Mountain gorillas are known to lick and eat decayed wood that contains high levels of sodium. Probably this is a comparable behaviour in bonobos. In the afternoon, the east bonobos backtracked their morning travel route, fed for the third time in the same maku trees and spent the night even further north and west, closer to the center of the home range of the west group. Actually, the east and west group nested only eight hundred meters from each other that night. Only the next day we would really realize how close this is for bonobos.
It took a while for the morning teams of both groups to grasp what happened that morning in the forest. The east group fed in a maku tree and slowly travelled northeast. The west group, by contrast, left the nest site early and at high speed, direction: straight east. The west researchers had difficulties keeping up with the bonobos and Lambert, following the east group, was surprised when around 7:30 am he saw a couple of females he knew from the west group! A fusion of two separate bonobo communities was happening. There was commotion, screaming, travelling. Most bonobos were lost out of sight. One of the researchers met up with Lambert, who said he had seen one of the west bonobos. Total confusion. The few (west) bonobos who stayed behind tried to catch up with the others to the east. Eventually both teams crossed the Bompusa and caught up with a couple of west bonobos on the east. In camp we got a message at 9:30 about the crossing and that Lambert was now searching on the east again. About an hour later we got a second message that confirmed the intercommunity encounter: females of both groups were seen in the same tree. We decided to all go in the forest to witness this special event. What we saw was really special. The two groups totally mixed, travelled together for about seven hours and fed in the same feeding trees. Individuals of the two groups groomed and copulated with each other. Intergroup encounters in other primate species are usually hostile, with the retreat of one of the groups ending the encounter. Each group tries to defend the resources in its home range. Chimpanzees even kill members of neighbouring communities. Why is this so different in bonobos? Do females play a special role? Female bonobos generally disperse to another community when reaching sexual maturity. Would females who associated a lot with each other during the encounter have lived together in the same group before? This is the first intercommunity encounter documented in detail at LuiKotale after more than ten years. Encounters with other, unhabituated groups must have happened before, but because the individuals of the other community will flee upon seeing humans around, it is very hard to grasp what happens during such an event. The days after the temporary mixing of both communities, the east community was missing two subadult females, but gained a new one. For the west group it was the reverse. Probably very few people have actually witnessed dispersal of subadult female bonobos between communities. Can a bonobo day get more memorable than that?

 

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Lieven in congo

At the moment Lieven Devreese is staying at LuiKotale, a bonobo research site of the Max Planck Institute for Evolutionary Anthropology in the vicinity of Salonga National Park, Democratic Republic of Congo. Lieven is a research assistant working on habituation of a second group of bonobos and he hopes to get to see some golden-bellied mangabeys as well. Here you can read more about his 10-month adventure.