New research shows that orangutans formulate and share future plans with others in their troop.

Very few animals have revealed an ability to consciously think about the future—behaviors such as storing food for the winter are often viewed as a function of instinct. Now a team of anthropologists at the University of Zurich has evidence that wild orangutans have the capacity to perceive the future, prepare for it and communicate those future plans to other orangutans.

The researchers observed 15 dominant male orangutans in Sumatra for several years. These males roam through immense swaths of dense jungle, emitting loud yells every couple of hours so that the females they mate with and protect can locate and follow them. The shouts also warn away any lesser males that might be in the vicinity. These vocalizations had been observed by primatologists before, but the new data reveal that the apes’ last daily call, an especially long howl, is aimed in the direction they will travel in the morning—and the other apes take note. The females stop moving when they hear this special 80-second call, bed down for the night, and in the morning begin traveling in the direction indicated the evening before.

The scientists believe that the dominant apes are planning their route in advance and communicating it to other orangutans in the area. They acknowledge, however, that the dominant males might not intend their long calls to have such an effect on their followers. Karin Isler, a Zurich anthropologist who co-authored the study in PLOS ONE last fall, explains, “We don’t know whether the apes are conscious. This planning does not have to be conscious. But it is also more and more difficult to argue that they [do not have] some sort of mind of their own.”
1 Capuchin monkeys appear to have a sense of fairness, insisting on receiving as good a food reward as their peers for performing the same job.

2 Scrub jays can relocate food that has been hidden for months and may even remember how long it has been stored. The jays also anticipate potential thefts and will relocate their food if they think another jay has spotted it.

3 Rhesus macaques will not pull a chain that brings them food if they think it will harm a fellow monkey.

4 Male voles may be able to predict when a female will be most fertile and, at the opportune time, revisit the location where she was last seen.

5 Bonobos and orangutans can use tools to retrieve food and then save their tools for later use.

Monogamy may have evolved to keep baby-killers away


Social monogamy – when a male and female of the species stick together for the long term, although may mate with others – is rare in mammals generally. However, it occurs in over a quarter of primate species, including humans, gibbons and many New World monkeys, such as titis.

To investigate what originally drove us to establish such pair bonds, a team led by Kit Opie of University College London and Susanne Shultz from the University of Manchester, UK, gathered data on the mating behaviour of 230 primate species. They selected behavioural traits associated with several possible evolutionary drivers of monogamy, including the risk of infanticide, the need for paternal care and the potential for guarding female mates.

Using data on the genetic relationships between the species, the team ran millions of computer simulations of the evolution of these traits to work out which came first.

All three were linked to the evolution of monogamy but only behaviours associated with infanticide actually preceded it, suggesting that this was the driver. Suckling infants are most likely to be killed by unrelated males, in order to bring the mother back into ovulation.

With pair-bonding in place, not only would a mother have a male to help protect the infant from marauding males, but there would then be the opportunity for the male to help care for it by providing extra resources. This means the infant can be weaned earlier, again reducing the chance of it being killed.

“Until recently, reconstructing how behaviour evolves has been very tricky as there are few behavioural traces in the fossil record. The statistical approach we have used allows us to bring the fossils to life and to understand the factors that have led to the evolution of monogamy in humans and other primates,” says Shultz.

Carel van Schaik, a primatologist at the University of Zurich in Switzerland says the results are solid but questions whether they can be extrapolated to humans. He says evidence suggests that humans were never really monogamous and that the monogamy we see today in many cultures is socially imposed.

Shultz counters that there is fossil evidence pointing to monogamy in australopithecines, the hominin genus from which modern humans descended.

“Although we suggest that infanticide may help explain the evolution of monogamy in humans, we do not argue that it is the only factor nor that monogamy is universal,” Shultz says. “I would suggest that where infanticide risk is high, as it would be with our ancestors, having a father provide protection and care would facilitate the evolution of the modern human extended childhood.”

Journal reference: PNAS, DOI: 10.1073/pnas.1307903110