Foraging and it's influence on group structure
Because fruit trees in Borneo – more than Sumatra – are somewhat distant from each other and do not provide much fruit, orangutans travel up to four kilometers per day to find fruit, bark, leafs and insects for food. It is probably because of this that orangutans –unlike other great apes - mostly live alone, but in overlapping territories. Smaller groups consist of one female with one or two offspring. Males only join these smaller groups for a few days and stay with the females only for mating.