I spend my days alternating between three troops of Verreaux’s sifakas. Two of my troops contain six individuals and one troop contains seven. Verreaux’s sifaka group size ranges from one individual to up to ten members. Here in Berenty, I’ve seen quite a few groups with six or seven individuals. Although, group size is much smaller in the spiny forest, which is very dry and where food is potentially limited.
This is one of the disadvantages of group living. Living in a group also means that primates must get along with each other. Just think of a time when you didn’t get along with a sibling or a roommate. Energy must be invested in maintaining harmony within the group. Sifakas usually get along pretty well with each other, from what I have observed. There isn’t a whole lot of social interaction. I’ve only seen some sort of aggression a few times, usually a quick squabble over food. I’ve seen the sub-adults play wrestling with each other twice now, but otherwise these primates mainly feed, rest, and groom themselves.
|Troop clinging to trees|
Many variables affect the size of a primate’s group: food availability, space, predation, etc. If the local habitat is reduced drastically by human activity, a primate may not be able to disperse into new territory to find mating opportunities outside of its natal group, causing tension and aggression within the group.
Critical thinking: Can you think of other instances in which human activity may affect the group size of a primate population?