Are you my baby? Why males might care for infants that are not their own

Written by Laura Abondano

YASUNI BIOSPHERE RESERVE, Ecuador – Guava, a baby woolly monkey, jumps off her mother’s back and lands on the back of Gordon, a male from one of the groups of woolly monkeys living at the Tiputini Biodiversity Station deep in the Amazon rainforest. Gordon continues moving a few meters in the tree with Guava on top of him before he sits down to rest with the baby still on his back. Guava’s mom, Guayaba, approaches Gordon and while the adults sit down to rest from a long journey, the baby plays with Gordon’s tail over and over again.

Lowland woolly monkeys live in groups where females typically display sexual behaviors that invite males to copulate with them. In fact, it is not unusual to see a female mating with multiple males in the same day, making it difficult for males to be certain of who they are fathering. Interestingly, males are often seen carrying, playing, grooming, or socializing with young infants, just like Gordon with Guayaba’s daughter, Guava. But not only are males tolerant with young infants, they also seem to be interested in maintaining close proximity to females with infants. What is very intriguing is why males engage in these friendly behaviors with infants given that they are not guaranteed to be the father.

As part of my doctoral research, I am studying how adult male woolly monkeys interact with infants to understand why it may be advantageous for males to have these strong social bonds with the infants or their mothers. Among primates, baboon and macaque males are known to form ‘friendships’ with mothers in their social groups. Mothers may be interested in creating these friendships given that these so-called male ‘friends’ may be offer protection or share food with the female and her offspring. But what do males gain from investing time with these females? Shouldn’t they be looking for other females to mate with?

If a male suspects that they may be the father of the infant, a strong relationship with the infant or his mother may increase the chances of survival of their own offspring. However, woolly monkey males have low certainty of who they are fathers to given that females may have copulated with other males during the previous mating season. It is possible that males may be interested in forming strong social bonds with females who have infants that are not necessarily their own, in order to increase the chances of the male mating with that female afterwards. This behavior is often seen among males that use their friendships to compensate for their low ranking position in the dominance hierarchy or reduced attractiveness as mates.

Among woolly monkeys, however, it is still unclear whether male relationships with infants and their mothers represent care for their own offspring or whether it reflects a male strategy to strengthen social bonds with females in order to increase future mating opportunities. Establishing paternity relationships between males and infants is the next step for our woolly monkey research team at UT-Austin, which will clarify whether males are really caring for their offspring, or whether they doing so to ensure their future reproductive potential.

In this video a small male infant, Dax, transfers from his mom, Darlene, on to a small adult male, Dash, and crawls around for a few seconds before transferring back to mom.

 

It’s Raining Monkeys!

Written by J. Mayo

In the four months that I have been working with the woollies here at Tiputini, I have seen seven monkeys fall out of trees. Thankfully all of them have been just fine, getting up and carrying on monkey business as usual. It’s not something I expected to encounter working here though, especially not at this rate. With their prehensile tails, incredible ability to judge distance and branch stability, and mad jumping skills, you would think they would have this arboreal thing down pat, right?

Photo of female woolly leaping through the trees. Photo was taken by Tim Laman from the canopy walkway at TBS. To read about how Tim took this picture click here.

Let’s take a second to think about reasons why woollies might fall out of trees:

R.I.P. Dear Digit

Written by K. Ellis

I got some pretty heavy news my first day back to the station. While searching for a few of our radio-collared animals, I heard one of my favorite monkeys on mortality (when there is no activity the collar will pulse much faster than the normal rate to alert the researcher that either the animal has died or that the collar has fallen off).  We pinpointed the collar to a large tree fall in the middle of D’s home range, but were unable to actually locate the collar before nightfall. I had the highest of hopes that Digit had managed to rip off the radio-collar and was now roaming the forest a free man. However, this fantasy would never play out as we found what remained of Digit and his collar under the tree fall the next morning. Digit’s cranium was intact and many of his bones were concentrated in one area, directly under the tree that had fallen. Thus, we have ruled out predation as the cause of death. The question remains, however, was Digit snoozing away when the tree went and he somehow got pinned under the tree as it fell or was he already injured and unable to move quickly enough to get out of harms way in time? Only poor Digit will know.

Digit was first identified as a subadult male in 2008 and noted to have two missing digits on his right hand for which he later acquired his name. In July of 2014 he was fashioned with a radio-collar allowing us to track him and his group. By this time, Digit had grown into a strapping adult male. Over several months of observation, Digit was noted to be a kind monkey and an integral member of the group. While he could often be found socializing with the moms and infants of the group, his true passion was to gallivant through the jungle on his own or with his trusty sidekick Docket (another adult male of the same age). And, although he was not much of a ladies man, he did have some successful copulations while under observation. Who knows maybe come summer we’ll have some little Digits running around (and Digit, or at least his genes, will live on)…