Ever since I read Manipulative Monkeys last year, I’ve been bugging Susan Perry to do a Q&A. She’s been super nice, but, you know, she has things like a job, field work and LIFE to attend to! I’m happy to say that she has found the time to answer my questions and it has been well-worth the wait. Thank you, Susan! I hope readers will enjoy this as much as I have!
- How did you end up as one of the world experts on white-faced capuchins (Cebus capucinus)? I was originally attracted to capuchins because I was interested in the evolution of intelligence. Comparative anatomists had discovered that capuchins (and the closely related squirrel monkeys) had the highest brain-to-body ratios of any nonhuman primate. At that point in my career, almost all of the data on primate intellect came from the Old World monkeys and apes – mainly from the species most closely related to humans – which meant that it was difficult to know whether large brain size and the presence of particular intellectual abilities were shared due to phylogenetic inertia (traits shared due to recent common descent) or were shared due to the fact that they shared some common adaptive challenge. Because capuchins were such outliers among New World monkeys with regard to their large brains, and because New World monkeys split off from our lineage ~42 million years ago, they provided a nice test case to see whether particular factors that we were assuming were important in selecting for large brains in humans and their closest relatives were also present in these brainy New World primates.
It was this debate that drove me to start a study of capuchins when I was a graduate student. And once I had met them, I was hooked. They turned out to have a complex society and highly variable and interesting behavior. Clearly there was a lifetime of work to do with this species, if I had the patience and tenacity to do it. Furthermore, Costa Rica was a lovely country – the sort of place where I felt comfortable returning year after year, even after starting a family.
- Capuchins have tons of brain power and personality. How would you describe them to someone who isn’t familiar with this species?
It is sort of like watching cartoons all day: they are constantly in motion, keeping busy with their social machinations as well as their constant quest to rip apart the forest in search of food. You have the sense that their brains are always turned on high power, no matter what their activity. In a social context, you can see their minds racing as they monitor their group mates, frenetically groom their friends, pick fights with their competitors, solicit aid from their allies, and studiously observe the foraging behavior of more experienced monkeys. Even when foraging in relative isolation, they are always mentally and physically engaged with their environments, as they tear apart trees looking for hidden grubs in the trunks or conquer the mechanical defenses of unripe fruits. Even when resting in a rare peaceful moment, their eyes are flickering about, looking for foraging opportunity or dangerous situation, and you know that at any second the monkey is likely to leap up and grab a passing insect or alarm call at a dangerous bird. There are no dull moments.
- When you are in Costa Rica studying the capuchins, what’s an “average day” like?
This is a difficult question because one of the reasons that I’ve kept at this for so long is that no day is the same. I love waking up in the morning and feeling virtually guaranteed that I’ll see something I’ve never seen before. Although I’ve spent thousands of days watching these animals, I’ve had at most one or two days in which I didn’t learn something new. But there are some constants. We start each day well before dawn, because we need to hike to the sleep site before the monkeys wake up. (They rarely sleep in the same place two nights in a row, and if we don’t want to waste hours or days searching for them, we need to be there when they wake up.) We follow these monkeys for about 13 hours. Most of the day they are foraging, traveling at a fairly slow pace, and occasionally pausing to groom and play. Whenever they encounter another capuchin group, we have to sprint to keep up with them, because the monkeys run as fast as they can (usually running away, if they are females, and chasing the other group, if they are males). The terrain is beautiful but difficult for large bipeds to navigate: it is composed of many river valleys and large hills/small mountains, covered with secondary vegetation. This environment has been heavily affected by human activity in the form of deforestation and fire, so the canopy is short (an advantage, for seeing monkeys) and the ground is thick with thorny brush and vines (which represent a major challenge for the observers). We’re constantly fighting our way through dense, prickly vegetation that is inhabited by stinging insects such as paper wasps. So despite the heat, we wear leather leggings and keep as much of our bodies covered as possible, to reduce the number of scratches and stings.
Because capuchins are so curious and pugnacious, they are excellent nature tour guides. They find and catch insects hidden in leaves or under bark. They wake up sleeping nocturnal creatures hiding in tree holes or thickets. And they warn us about snakes lurking under the leaf litter or below the surface of the water. We see so much more in the company of these animals than we would if we were walking through the forest on our own.
- The leading cause of death in your research animals is other capuchins. Can you discuss this?
Yes, in this respect they are very much like humans. The most dangerous enemy of the capuchin is other capuchins. This is particularly true for infants and adult males. The leading cause of infant mortality is infanticide: When a new male takes over the group and becomes the alpha male, he generally kills the unweaned infants. About 75% of adult male mortality is due to fights with other adult males. Most of these attacks are coalitionary attacks by groups of males against males from outside the group whom they discover alone, though we do sometimes see coalitionary killings of males who are members of the same group.
Because alpha males do almost all of the breeding, the competition to become the alpha male is very steep. And once males have finally attained that breeding position, they are eager to bring the females into estrus as soon as possible so that they can produce offspring before they lose the alpha position.
- What other threats are there to the monkeys at Lomas Barbudal and in Central America in general?
Capuchins have many natural enemies – boas, rattlesnakes, caiman, large raptors, coyotes, large felids, and humans, for example. But they are highly cooperative in their defense against these creatures and generally gain the upper hand against most of them.
Humans present the greatest threat to capuchins. The local people throw rocks at them and shoot them with rifles, mainly as a form of recreational hunting. Although capuchins are a popular food item in many parts of South America, they are very rarely eaten in Costa Rica, where the primary prey of hunters are peccaries, deer, armadillos, garrobos and pacas. Infant capuchins are often captured as pets, and this sometimes requires killing of the mother. We find at Lomas that monkeys are 2 to 3 times as likely to vanish or die on days when they are NOT accompanied by researchers, and we assume that this effect is mainly due to the protection that researchers provide them against human-induced mortality (because snakes and birds are not inhibited by our presence, and we are not with the monkeys when the shier nocturnal predators are actively hunting).
Human development often causes problems for capuchins even when the humans are not deliberately seeking to harm them. For example, many monkeys die every year on uninsulated electrical cables, or are killed by cars while crossing the road. Although it is hard to quantify the impact of fire and deforestation on monkey population dynamics, it seems inevitable that reduction of their food sources must have some effect on their ability to survive and reproduce.
- In a 2003 article you co-authored on capuchin interactions with other species stated “a group of ≥ 5 spider monkeys can usually displace capuchins from a feeding site, which howlers almost never do.” Given that both spider monkeys and howler monkeys weigh about the same, do you believe this is a function of spider monkeys and capuchins having more dietary overlap? Or howlers’ phlegmatic nature? Or something else?
I don’t recall the precise amount of dietary overlap between spiders and capuchins, but I doubt that it is much greater than the capuchin-howler degree of overlap. Howlers and capuchins frequently encounter one another at fruiting trees, and at Lomas the capuchins consistently succeed in evicting the howlers.
I think this is primarily due to howlers’ more phlegmatic nature. Both spider monkeys and capuchins are feisty, fast-moving creatures with hot tempers. Capuchins are not the sort to let sleeping dogs lie – they actively seek conflict. Howlers are not easily aroused, and they generally try to avoid trouble. Also, both capuchins and spider monkeys are more prone to cooperative aggression than howlers are. Capuchins routinely pick on other animals who are minding their own business, almost as if seeking an excuse to form a coalition with one of their allies. It seems to me that much of this bullying behavior is a relationship-building exercise for them.
- Do you have a favorite capuchin from all your years watching them in Costa Rica?
Tough question! I have so many favorites by now. I’ll mention just a few of them. Adult female Rumor and adult male Guapo are both favorites of mine because they invented such quirky social rituals, which I had the fun of documenting as they spread through the social group, becoming traditions. My favorite “Rumor tradition” is eyeball-poking, in which she inserts a friend’s finger in her own eye socket, up to the first knuckle. My favorite “Guapo ritual” is the hair biting game, in which he bites a huge tuft of hair out of his friend’s face and then plays a game in which they take turns forcibly extracting the hair from one another’s mouth, passing it back and forth until the hair is all gone; then they start over with another tuft of hair.
I am a fan of Pitufo because he overcame a major handicap in his quest to become alpha male. He seemed like the brightest and most socially competent member of his cohort when he was very young, and we predicted he would become an alpha male. But then he lost his left hand and forearm in an accident when he was a juvenile, and this is probably why he greatly delayed his migration from the natal group. He became highly skilled at foraging and fighting with his one arm (using his stump both to balance food on while processing with the hand, and also as a club to whack his competitors). And eventually he became a highly formidable and successful alpha male. Check out Pitufo’s Facebook page (look for Pitufo Mono) to see his full life story.
Took is another favorite who eventually became an alpha male despite the handicap of losing all but one of his canine teeth (the primary weapons of a male capuchin). You have to be enormously clever on the social front to avoid death when you have so few teeth!
My research team is currently fascinated by Winslow Homer, our youngest male migrant. It seems that he migrated accidentally, when he lost contact with his family during an aggressive intergroup encounter. This adorable infant, the unweaned son of the alpha female in his natal group, was immediately adopted by the new group and is thriving, due to his good nature and exquisite social skills. You can read more about Winslow at winslowhomerday.net or by visiting the Capuchin Foundation Facebook page.
And I can’t neglect to mention my favorite capuchin duo: Pablo and Mezcla, the benevolent dictators of Rambo’s group. This dynamic duo produced an incredible number of descendants and was highly effective in protecting them from infanticidal males and predators. In one memorable instance, they rescued their daughter from the coils of a boa. Pablo has had 25 children, 105 grandchildren, 43 great-grandchildren, and 1 great-great-grandchild. Mezcla has produced 8 children (all but one of which survived), 30 grandchildren and 18 great-grandchildren. The social atmosphere in Rambo’s group was great during their reign: imagine massive numbers of frolicking kids romping in the leaf litter, playing games daily.
- What about a favorite story from the field?
Some of my favorite monkey moments are those in which monkeys offer truly heroic assistance to other members of their group. For example, when infants’ mothers die or abandon them, it is heart-warming to see other monkeys offering them rides, milk, and protection. When a mother dies, typically all of the other females in the group allow the orphan to nurse, and this often makes the difference between surviving and not surviving. Here are a few good memories of that sort: When infant Cayenne broke both of her back legs and had to locomote by dragging herself along on the ground, Shylock, an adolescent female, carried her a lot, providing her with protection from ground predators and making it easier for her to keep up with the group while she healed. When Peeves’ mother Vandal was severely wounded and vanished from the group for several days, his (older) niece Monster adopted him and provided milk until his mother had recuperated to the point where she could rejoin the group and resume nursing him. When first-time mother Darwin decided that she wasn’t ready for motherhood, Gerber (an adult female with a similar aged infant) adopted her baby and raised both infants together – truly an act of maternal heroism. Gerber never got any rest, with both infants playing on top of her as she struggled to carry them everywhere.
- Do you have any advice for people who might be thinking of having a capuchin or other primate as a pet?
Please don’t do it! Both you and the monkey will have regrets. No matter how good your intentions are, and how much you love the monkey, it is a recipe for disaster. Dogs and cats have been co-evolving with humans for long enough that human and pet can communicate effectively and satisfy one another’s emotional needs. Wild monkeys are another story entirely. Capuchin monkeys desperately need the companionship of other capuchins to form the sophisticated sorts of relationships that their minds have evolved to crave. Also, as I’ve mentioned above, they have evolved to forage destructively, and they have hot tempers and a propensity towards unrestrained aggression in some situations. This is particularly true of adolescent and adult males. Capuchins love a good destructive foraging challenge and would be happy to shred your pillows or chew your wooden furniture looking for hidden invertebrates. There is a reason why those “helping hands” monkeys have their teeth extracted! Believe me, no monkey wants to have its teeth extracted in order to become someone’s pet.
I frequently get email from distraught capuchin owners saying that their sweet baby monkey has developed a temper and is biting people or destroying their home now that it is reaching adolescence. Of course it is! This is part of its natural development.
Every time I see a pet monkey, it has little nervous ticks and stereotypies that are indicative of extreme stress when they occur in wild monkeys. Pet owners and zookeepers are so used to seeing such behaviors that they view them as normal; but those of us who spend time with normally developing monkeys in the wild are all too aware that these are signs of psychopathology. Monkeys need a lot of intellectual stimulation, both from their physical environments and their interactions with other monkeys, in order to develop into happy, psychologically normal adults, and humans cannot satisfy these needs.
Another point to remember is that once a monkey has been raised by humans, it cannot be safely returned to the wild (at least not without a lot of expensive rehabilitation). There is much that monkeys need to learn from other monkeys in order to be competent in the wild. The best solution is to keep monkeys in the wild to begin with.
The following website provides more useful information about capuchins as pets:
There are many ways to love animals, and having a pet is just one of those ways. I have found that there is much pleasure in simply watching these animals from a respectful distance, and seeing how they interact with one another. If you want cuddling and an intense emotional bond with your animal companion, stick with a dog. If you can stand to just be accepted as a neutral feature of the environment by the animals you admire, rather than being the central figure in their lives, then try observing animals in their natural habitat, doing what they normally do. It is rewarding in a different way than having a pet is rewarding.
10. If someone reading this wants to help capuchins, where would you direct them?
The Wild Capuchin Foundation (capuchinfoundation.org) was established to support research, education and conservation of wild white-faced capuchins. By supporting this organization, you can help support the Lomas Barbudal Monkey Project, a 25-year research project that has documented in detail the lives of ~500 wild monkeys living in 12 social groups for up to 5 generations. Research, education and conservation are inextricably linked in this project. There is no better protection for these wild animals than the “escort service” of a team of biologists who are committed to preserving them. Our presence deters poachers, and our presence in the forest helps alert the park service to problems that need to be resolved, such as fire or un-insulated power lines too close to branches. The Foundation is committed to bringing the project’s research findings to the general public (and particularly to the communities adjacent to the forests where capuchins live), to enhance local understanding of the value of these animals and the endangered tropical dry forest that is their home.
The Lomas Barbudal Monkey Project is always accepting applications for volunteers who can help with data collection as well as outreach into the public schools in Costa Rica.
For people wanting a more hands-on relationship with animals, there are various monkey rescue or rehabilitation centers around the world that accept volunteers to help care for captive animals that are former pets.
Of course, anyone who wants to make a difference for capuchins and other wildlife can spend some time volunteering in schools and youth centers in their own countries, educating children about wildlife so that they will become the sorts of adults who actively fight to preserve the habitats where wild animals live. We find that one of the best ways to divert the attention of young people towards promoting wildlife conservation is to tell them the life stories of monkeys, because these are animals that children can readily relate to and empathize with. The Wild Capuchin Foundation (capuchinfoundation.org) and the Primate Education Network (http://www.primateeducationnetwork.org) are two organizations (among many) that are happy to provide people with the educational materials they need to promote primate education in the schools.
11. What’s next for you? Are there more capuchin questions you want to answer or are you looking for new challenges?
There are always more questions to answer! The more data we gather, the better positioned we are to answer some of the most difficult and interesting questions in evolutionary biology, for which complete reproductive histories of large numbers of individuals are necessary.
My team is still pursuing our goal of documenting the life histories of these long-lived animals. We have been collecting data on the demographic circumstances, personalities and early life experiences of the monkeys born into our study population, and are now collecting data on the major decisions they make about where and when to migrate, whom to migrate with, and what kinds of parents to be. To answer the really important questions about the evolution of individual differences, we need to know the reproductive consequences of the strategies that individual animals employ – ideally by measuring lifetime reproductive success. This is an ambitious goal for a species that can live for several decades (close to 4 decades in our population).
We have observed major environmental changes in recent years, and this has inspired us to document the effects of ecological challenges such as major forest fires and droughts on the monkeys’ foraging strategies and reproduction. Rare ecological disasters can have major influences on the evolution of species if they have a big impact on their reproduction. But the impact of these events is hard to measure if there is no long-term baseline against which to compare current behavioral strategies, ecological contexts and population dynamics. The Lomas Barbudal Monkey Project has amassed enough baseline data on the monkeys’ behavior and reproduction to start answering these difficult questions. We are currently investigating the impact of a major forest fire on the monkeys’ diet, ranging patterns, and survival and reproduction.
We continue to be interested in issues regarding communication, negotiation of relationships, and trust rituals. We’re starting a new project investigating the function of “gargle” vocalizations. These are loud, raspy calls delivered primarily by immature animals and their mothers to adult males. Adult females direct them almost exclusively towards the alpha male, whereas immature monkeys also direct them at subordinate males. Males do not seem to appreciate receiving these signals: at best, they ignore the “garglers” but often they swat them away. We will be exploring the possibility that gargles are designed to test the male’s attitude towards the gargler, so that the garglers know where they stand with the males.