Monkey with a pet?

Updated: Aug 21, 2018

Every now and then I take a break from the physical sciences. I was particularly delighted when forwarded a charming diversion from the Journal of Primatology. After all, what is more delightful than a monkey, with their tiny people hands? A little monkey adopting an even tinier marmoset, that is what is more delightful.

The paper (available here) details the extraordinary relationship between a capuchin monkey and a young marmoset. Friends? Adoptive parent? Or even a pet? It is difficult to say for sure. There have been many reports of unusual pairings in captivity but it is uncommon in the wild. It should be noted that while this story takes place in the wild woodlands of eastern Brazil the animals were exposed to humans and regularly fed to encourage tourism.

Enter marmoset, stage left

The story first began when the group of monkeys appeared looking for food and someone noticed one of the monkeys was carrying an infant marmoset which the researchers named Fortunata. Little Fortunata tagged along each time the group appeared at the feeding area a couple of times a week. It clung to one of the adult capuchins just like their own babies would. Fortunata seemed particularly close to one individual called Dende.

A closer look required

Researchers noted this unusual behaviour. Surely an unusual quirck of evolution to be drawn to attempt to raise stray infants of any species you happen to come across. They followed the group for a week and monitored all movements closely. What they saw was a marmoset which not only maintained its own natural behaviour but happily was an adopted member of the monkey group.

Baby mine

Dende was protective of her tiny charge. Even fully grown Fortunata would only ever be a tenth of her size. Dende Carried her little baby around, she groomed it and pretended to nurse it. Interestingly when Dende or any of the group played with Fortunata they seemed to realise how small and fragile their playmate was, adjusting their force so as not to injury the marmoset. If the alarm call was sounded Dende would run and protect Fortunata and carry the marmoset to safety. Also even the dominate male was tolerant of the smallest member of the group as he would put up with a little marmoset hand stealing the odd bit of dropped fruit and nuts from him.

An independent marmoset

A lot of the behaviour noted suggests that Fortunata had effectively become a small capuchin monkey- but this wasn’t necessarily the case. Capuchins don’t eat gum from trees- marmosets and Fortunata do. Also sometimes the poor monkey-wanna-be was just too small to keep up. Capuchins are particularly acrobatic- marmosets would fit in your hand. Several times Fortunata just couldn’t keep up. Researchers saw the monkey groups swing off and abandon Fortunata in a tree while they cracked nuts below. Once for 5 hours none of the group seemed very fussed about the missing member. Fortunata also wasnt a fan of being carried. The capuchins would pick up Fortunata but soon the little marmoset would wrestle free and make its own why, despite this being somewhat difficult for the tiny creature.

A happy ending?

After the intense observation things carried on as normal with the whole gang arriving at the feeding station together. Then something changed. One day after over a year in the group Fortunata arrived alone at the feeding station. The same again the next day. And the next. Then never again. Where Fortunata went no one will ever know. Personally I like to think Fortunata is surrounded by many grandchildren telling tall tales of her youth with a troupe of giants.

As I said I am very much a physical science boy. Information is published only when reproducible, quantifiable and tested. The last line of the paper sums up the entire article beautifully and shows one of the major differences with my subject area:

“Becasue there are no other comparable cases to examine, we can draw no strong conclusions from this case”

So there we have it. We’ll have to wait for another marmoset to be adopted before we decide what was going on. But still, what a lovely tale.

Photo by Jeanne Shirley (Izar et al., 2006)