Orangutans are the most solitary of the great apes, but mothers appear to organise real playdates for their offspring. That is the conclusion of a team led by the Max Planck Institute of Animal Behavior, in collaboration with the University of Zurich, Universitas Nasional in Indonesia and Rutgers University.
At the Tuanan research station, on the island of Borneo, scientists have followed mother-infant pairs since 2003, from morning to night. Over some 15 years, they accumulated 32,000 hours of observation of 31 pairs.
The researchers found that mothers with young of similar ages shared more territory and that these young played together more often. On play days, and on the days immediately before and after, mothers travelled greater distances, moving into the other mother’s area, and spent less time feeding.
These encounters are rare, occurring on about 6% of the days observed, and play between the young lasts about 20 minutes in total. According to the senior author, Maria van Noordwijk, the study reveals a hidden cost of solitary life; it is not yet known whether this investment benefits the young later on.
