Chimpanzee Sanctuary Northwest

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aggression

Q&A: Why Cy is Missing a Finger and Other Notes on Chimpanzee Aggression

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Recently, we invited you to submit your questions. Joshua wanted to know: Why does Cy have only three fingers and a thumb on his left hand?

The short answer?

“No regrets.” – Rayne

As far as we’ve been told, Rayne bit off or severely injured the third digit of Cy’s left hand at some point during their time at their previous home in California. As to why she did it (if the accusations are indeed true), we need to step back a bit.

Chimpanzees can be incredibly aggressive. And I don’t mean traumatized research chimpanzees can be aggressive or chimpanzees kept in captivity can be aggressive. I mean that natural selection has endowed all chimpanzees, to varying degrees, with a capacity for aggression and a tendency to utilize it to achieve certain ends. In other words, it’s a normal part of being a social chimpanzee—a tiny fraction of their overall behavior, to be sure, but an important one.

When discussing aggression in chimps, we typically differentiate between intergroup and intragroup aggression. Intergroup aggression, or the violence directed at chimpanzees in other communities, has the distinction of being far more lethal. These attacks, often the result of stealthy raids into neighboring communities, are understood to be part of an evolutionary strategy to guard or gain access to territory (and thus resources such as food or potential mates). Intragroup aggression, on the other hand, tends to be a way that chimpanzees—particularly late adolescent and adult males—determine rank or status within the community. Lethal aggression does occur within communities (often in the form of infanticide or the overthrow of the alpha male) but at about half the rate of that between groups.

It’s almost impossible to describe to someone who doesn’t work with chimps just how violent chimpanzee fights can be. Their strength, speed, and agility are literally superhuman. Their screams and cries are deafening. And they can be seemingly ruthless, quite often ganging up on more vulnerable chimps. While their muscular arms and legs are used to grapple and pin, their ultimate weapons of choice are their large teeth and powerful jaws, which open wide enough to accommodate most any body part of an intended victim—though they usually select ears, fingers, toes, and, in cases of more extreme violence, genitalia.

Life for captive chimpanzees is very different from that of their wild counterparts. They don’t have the same kind of territories to defend, nor do they have the potential to acquire new resources by raiding and killing. But natural selection doesn’t typically endow us with knowledge of why we behave the way we do; instead we’re simply primed to behave in ways that tended to benefit our ancestors (humans are no exception to this). And captive chimpanzees are often presented with situations that stoke those very same intergroup prejudices—most notably, during social introductions. When we are integrating groups—or even riskier, adding a single chimpanzee to an established group—we have to overcome that same hostility toward outsiders that drives wild chimpanzees to attack and kill their neighbors. And this is where we may see the most severe forms of aggression. At CSNW, it once lead to a conflict in which one participant, Honey B, had to have her toe amputated, and another, Burrito, had to be castrated due to the severity of the wound to his scrotum. Neither injury was lethal, though in Burrito’s case it was largely because of timely veterinary intervention. In a way you could say that we’re fortunate, because chimpanzees have died in similar circumstances at many accredited zoos and sanctuaries. These are the stories that don’t always make it to social media, but instead are shared by keepers and caregivers over drinks at a conference hotel bar, finding comfort in others that understand what it is like to work in this crazy field.

Honey B

More often, we are witnessing the almost commonplace kind of aggression that serves to establish rank, form coalitions, and settle scores. Chimps, like humans, are status-seekers. Status may come with tangible benefits, but status itself is an intrinsic benefit, one that is apparently worth fighting for. Because this form of aggression serves to clarify relative dominance, we tend to see somewhat less of it in stable groups and more in groups that are newly formed, lacking a strong leader, or undergoing a leadership transition. It also appears to be more common in groups with unusual compositions (in terms of age, sex, etc.) or ones with chimps that lack social experience. Regardless, wherever there are two or more chimpanzees, there will be at least the occasional fight. One study at an accredited zoo found that their chimpanzees were wounded in fights ten times per year on average. Thankfully, along with their superhuman fighting abilities, chimps possess a superhuman ability to heal and an equally superhuman tolerance for pain.

Jamie’s group has been together for over 18 years now. You’d think that they would have achieved some level of stability after all this time. But they epitomize the problem with a lack of leadership and atypical rearing. When they arrived from the lab, we did a quick inventory of missing ears and digits: Negra was missing half an ear, Annie’s ear was torn almost in two, Burrito was missing a fingertip, Missy was missing most of a pinky, and Jody was missing toes (though at least one was said to have been severed by a guillotine cage door). Those are just the ones I can think of off the top of my head. We do the same inventory of every group that we rescue, and relatively few adult chimpanzees arrive at sanctuary with all ears and digits fully intact—unless they, like George, lived largely alone.

Negra
Missy (R)

We’ve done our fair share of repairs and amputations here at the sanctuary, beyond those of Burrito and Honey B. One morning, the chimp house was perfectly still until a shriek erupted from Front Room 4. We looked over to see Burrito fleeing and Foxie sitting there in shock, a chunk of her ear laying on the bench beside her.

There’s a trap that I try to steer people clear of (and one that I have to try to avoid myself), which is to assume that every action that a chimpanzee takes is part of a grand Machiavellian drama; that each squabble is a deft maneuver towards some strategic aim. Did Burrito bite Foxie’s ear off because he wanted to outrank her? Was he trying to form an alliance with Jamie, who has positioned herself as Foxie’s chief antagonist? Possibly. That kind of thing certainly happens. But again, we have to bear in mind that the algorithm of natural selection has in many cases done most of the calculations for us in advance, and has left us with some rather dumb emotions to carry out all the work. Status might ultimately bring more food and more mating opportunities, but we start fights because we’re pissed. We overcompensate because we’re insecure. We anger others because we are socially inept. We gang up on the weak because we crave power. We ostracize those who are different because we want to belong. In other words, we can describe chimpanzee behavior in terms of ultimate causes, but as socially savvy as chimps are—and they are very savvy—the proximate cause for any given fight or injury is likely that they are bundles of emotions, both noble and ignoble, with the strength of several humans and teeth like railroad spikes.

As for Cy’s finger, I certainly don’t know what happened, but knowing him now, I’d be willing to place a bet: Rayne was going after someone she was mad at and Cy was injured trying to stop the fight. That’s the other thing about chimp fights, at least in captivity—they rarely end as they began and the chimp with the most injuries was probably not involved at the start.

Mercurial Males

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Male chimpanzees can be pretty cruel to the females in their group. Why are some of them such jerks sometimes?

From an evolutionary perspective, this aggression is thought to serve two functions. First, it may serve the purpose of establishing dominance. This is particularly true for adolescent males, who rise through the ranks in their communities by establishing dominance over each of the females before working their way into the adult male hierarchy. But it may be true for adults as well, as these displays of dominance can signal their fighting ability to other males in the group without the increased risks associated with directing aggression towards those other males.

Second, research suggests that, in adults, female-directed aggression by males also serves as a form of coercion. In some communities, males that exhibit more aggression towards females have been shown to sire more offspring by either increasing the probability that a female will mate with them or decreasing the probability that she will mate with someone else.

Most captive male chimpanzees, Willy B included, don’t even exhibit copulatory behavior, since they were raised in such atypical physical and social environments. It’s interesting then, and unfortunate, that this predisposition towards female-directed aggression nevertheless persists.

These same adult males and females can at other times be quite playful with one another. In wild environments, this appears to be more evident when resources are abundant, which suggests that play—known to have significant social and developmental benefits in adolescents—also benefits adults when time and energy are available. This may be why we see so much play in adult captive chimpanzees—after all, in better environments, most of the nutritional resources they need are all provided to them. Of course, some forms of play can be a mechanism to ease an underlying tension, which may be why play is so common before feeding times. But in most cases, it’s hard to see it as anything other than two chimps having fun.

When we study other animals, we don’t think in terms of “good” and “bad” behavior. Instead, we try to describe what is and develop explanations for how it came to be that way. Living with chimpanzees on a daily basis, though, can challenge this kind of impartiality. You cheer when you see them playing together and film it so others can share in their fun. And you become frustrated and upset with them when they fight. And before long you find yourself—biology be damned!—rooting for Honey B, who would sooner die than give an inch to any of those dumb, bullying boys.

 

Superhero

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Two things to note before you watch the video below:

  • The video shows the chimps fighting. If that’s not your cup of tea, we understand.
  • If you choose to watch, you must do so with the sound on so you can hear the narration that attempts to explain some of what you will see. The chimps will be loud at first but we’ll turn down the volume on the screaming and pant-hooting early on in the video.

Showing the chimps in your care fighting may not be what they teach in nonprofit PR/fundraising school, but I’m always hopeful that people can learn to understand and appreciate chimps as they are while continuing to support them and the sanctuaries that care for them. Sanctuary life is filled with fun, happy moments. To a lesser extent, it also contains unsettling, even terrifying moments. They are still chimps, after all.

As I mention in the video, we are often of two minds in this job. First and foremost, we are caregivers, fretting over each bump and scrape the chimps receive and agonizing over every decision we make with regard to their care. This is the mind we inhabit in the midst of a conflict. But we are also primatologists and enthusiastic observers of chimp behavior. We are the people that, like many of you, were glued to Jane Goodall documentaries as kids and who find the complexities of chimpanzee social dynamics endlessly fascinating. And as I watched the footage of this conflict, I felt my 20-year-old self, just entering the field, marveling at each and every interaction. Perhaps you will feel the same.

If by chance you are new to Chimpanzee Sanctuary Northwest, this group is the result of the integration of two smaller groups: A group of six, led by Cy, and a group of three, led (mostly) by Willy B. Almost immediately after their integration in 2022, Willy B accepted Cy’s dominance and established himself as the #2. But Willy B does not have Cy’s social skills, and from time to time that can get him into trouble with a few others in the group.

Similar to what is seen in the literature, the rate of conflict in this larger group hasn’t gone down all that much since the initial integration; it ebbs and flows and at times it may even be higher. But the conflicts are shorter and result in fewer injuries (I don’t believe in jinxes, I don’t believe in jinxes, I don’t believe…). This conflict was unlike most in that it lasted a long time; as I say in the video, this is likely because of Gordo’s unique inability to calm down. Prior to the integration of these two groups, Gordo would occasionally get this upset with Cy. Cy, having nearly unlimited patience, would just let himself be chased by Gordo until Gordo eventually wore himself out. But that was a low-ranking male venting at the alpha, who clearly felt no threat to his own safety or status. Here, the relationships between the lower-ranking males is less well-defined. And thus the stakes are higher.

There’s an important caveat that I should mention here: I describe some of what I think I’m seeing, but any time I read a matter-of-fact description about relationships and behaviors as complex as those in chimpanzees, my BS detector starts to go off. Half the time we just don’t know or we drastically oversimplify things. So let me admit that up front. And this, I should add, is with the benefit of instant replay and slow motion—now maybe you can see why we say we don’t always know what happened in real time when the chimps get in fights.

Oh, and another one: Cy gets top billing in this blog post and he certainly has the most influence over the outcome, but boy that Honey B has some guts. And there are so many other interesting interactions that I didn’t touch on, many of which are also influential. Alpha males always get the headlines while the females quietly do much of the work. But this alpha sure did put on a show.

This video also doesn’t include what happened after the fight, which in some ways is the most interesting and important aspect of chimpanzee relationship formation and maintenance.

I could probably go on all day about this so I’ll stop here. Feel free to ask questions!

A Natural History of Jerks

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Male chimps can be jerks. True, females can also be jerks (see: Chimpanzee, Jamie), and not all males are jerks (at least not all of the time). There is an exception to every rule. Nonetheless, it is undeniable that chimpanzee jerkishness has a certain maleness to it, just as chimpanzee maleness contains a certain jerkishness.

But just as not all male chimps are alike, so too is it true that not all jerks are alike. While this is by no means an an exhaustive examination of the topic, here we will distinguish between two types of jerk: Those jerks who wreak havoc blindly, as if possessed, and those who inflict their jerkiness with forethought and intention.

To illustrate the former, let’s turn to our dear friend Willy B. Today I watched him sit peacefully in the shade beneath a climbing structure on the Bray, his 2-acre habitat, surveying the yard for remnants of a the day’s forage. When the forage was finished, he quietly returned to the indoor enclosures. It being mid-afternoon, however, this peaceful Dr. Jekyll was suddenly and inexplicably transmogrified into a raging Mr. Hyde. Apropos of nothing and with no other chimps in sight, he began to bang on the food chute with the back of his wrist. The noise and vibration shattered the calm of the afternoon and soon the others were up from their naps. With hair on end, they circled each other in the confines of the front room area. Some began to pant hoot, which in turn raised the tension in the room even further. Minutes went by. The banging was incessant. Others began to stand bipedally and swagger. Bang, bang, bang. The noise swelled and soon came to fully occupy the space where thoughts would normally occur, making it impossible to do anything but join in the chaos. Bang, bang, bang…

BANG! A fight breaks out. The swirling mass of chimpanzees, now screaming, races from the front rooms through the chute and out to the Bray. Willy B climbs to the top of the tower and, with a fear grimace, watches as the other chimps threaten and hit one another. But he is not angry. Instead, he is scared and confused. Because he is once again Dr. Jekyll, wondering what on earth could have caused such tumult below.

Interestingly, this fight contained within it, and was indeed amplified by, the actions of our second type of jerk. Are you familiar with the admonition, common in both comedy and politics, to never punch down? For male chimpanzees, punching down is not only accepted in certain circumstances but is in fact a right of passage. As Craig Stanford states in The New Chimpanzee,

[Adolescent male chimpanzees] don’t submissively pant grunt to one another, and dominance among them is hard to discern. But once a young male reaches adulthood, he begins to climb to higher rank by taking on and intimidating each adult female. When he has risen in status above the most dominant female, the young male finds himself at the bottom of the male dominance network. Only time and repeated jousts with higher-ranking males will determine his ultimate highest status. (p.42-43)

According to some researchers, adolescent male chimpanzees routinely harass adult females as a low-cost way method of honing their competitive skills before testing them in the much riskier world of male competitive dominance. Gordo is well beyond adolescence, but his actions are often reminiscent of a chimpanzee stuck permanently in the liminal space between the female and male hierarchies. While size does not dictate rank, his more diminutive stature makes it unlikely that would challenge Cy, Terry, or Willy B directly. His social skills are of little help, either. He is able, however, to dominate Honey B. Usually.

As the dust on the Bray began to settle, the chimpanzees worked their way through the chute and back to the greenhouse. The screams had subsided and all that remained was Honey B’s diminishing whimper. This, thought Gordo, was the perfect time to assert himself. As she approached him, he hit her across the back and ran straight back to the Bray, knowing that she was afraid of the outdoors and wouldn’t have the courage to follow him.

He reached the platform and turned to watch Honey B screaming at him helplessly from the end of the chute.

Is it any less indecent for Willy B to cause daily disruptions to the harmony of the group simply because they are born out of blind rage and not malice? I make no claims as to the relative moral status of these two varieties of jerkishness. Nor, again, do I intend to cast all males as irredeemably jerkish. But in my experience, they do seem on average to contain each type of jerkishness in greater proportion than their female counterparts.

And as to whether these same tendencies prevail in my own species, I claim ignorance.

What Makes Us Tick

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We’ve written a lot about that ways that Positive Reinforcement Training (PRT) can improve the lives of captive animals, including—or should I say especially?— chimpanzees. Chimps are so powerful and so strong-willed that often the only way to get them to reliably engage in certain behaviors, whether it’s allowing the stick of a needle to administer medication or leaving an enclosure so it can be cleaned, is to ensure that it is by their own choice.

One area where PRT is particularly useful is during meals. Some dominant chimps take a What’s mine is mine and what’s yours is also mine approach to food, leaving other chimps in their group hungry, anxious, or both. A technique known as cooperative feeding can encourage dominant chimps to allow their group mates to eat their meals in peace by rewarding tolerance for others eating nearby. The trick is not to forcefully assert our own sense of fairness but to show certain chimps that it can be worth their while to chill out a bit. Sure, you could steal someone else’s food, but if you allow everyone else to eat you’ll get something even better for a whole lot less effort.

We’ve been using this technique with Jamie lately, as she has been giving both Foxie and Annie a hard time during meals. It’s certainly not unheard of for Jamie to steal food to assert her dominance, but the recent uptick has had her group mates on edge and unwilling to even take certain foods. Why all of a sudden? It’s hard to say for sure, but it’s possible that Jody’s passing left some ambiguity within the hierarchy and Jamie may have been feeling the need to remind everyone that there will be no changes at the top. Subtle, she is not.

One of the keys to effective training is finding the right unconditioned reinforcer, which is the natural reward that often follows the click or whistle, telling the animal that behavior is worth doing again. In almost all of the training we do—that is, the training the occurs during formal sessions—that reinforcer is food. Sips of juice, pieces of chopped up fruit, and bits of primate chow are all effective, though each individual will be motivated according to their own preferences. For Jamie, that means a click! and a piece of preferred food or drink every time she watches Foxie or Annie receive something she might want to steal. And if she stays at her station throughout the entire meal, she may even get a special treat, such as a whole clementine, at the end.

But food is such an efficient reinforcer that we sometimes forget that it’s not the only one. For Jamie, flattering her ego may be an equal or even greater reward. That’s not to say that Jamie doesn’t appreciate the special treats, but the extra attention from her caregivers and special status at mealtimes may being doing some if not most of the work. Perhaps when you are recognized as the boss by the humans in front of all your group mates, there’s less need to constantly remind everyone.

We’re all motivated by a handful of basic desires – to be noticed, to be appreciated, to be respected. Figuring out what makes someone tick can go a long way toward influencing their behavior. Because in the end, Jamie isn’t as complicated as she would appear: all she needs is the unquestioning loyalty, unreserved admiration, and complete and thorough submission of all those around her, human and chimpanzee, at all times. That and a few extra pear slices and she’ll be happy to mind her own business at lunch.

Conflict and Reconciliation

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A quick word of warning: If you do not wish to see footage of chimps being aggressive towards one another, please skip this video.

Recently, Grace posted to our social media accounts asking people to submit questions for Q&A posts on our blog. One of the questions jumped out at me: What is the best and worst part of your job? I immediately thought of dozens of things I like best about this line of work – we get to provide the chimps with life-changing and long overdue experiences like going outdoors and climbing trees, we help them form new friendships, we are treated on a daily basis to displays of intelligence and emotion that many people still believe are reserved for humans alone, and we get to do the thing we love with people we enjoy working with in a breathtakingly beautiful environment. Oh, and I get to drive a tractor sometimes. Maybe I should have put that first? Anyway, how could I choose just one “best” thing?

But when it comes to the worst part of the job, there’s no question in my mind what it is: it’s the violence.

Chimpanzees are naturally aggressive. Not all the time, mind you, or even most of the time. Aggression actually makes up a very small part of their daily activity and is just a tiny facet of their overall demeanor. Most of their waking hours are spent resting, quietly grooming, exploring, and playing. And most of their interactions with one another are overwhelmingly friendly and cooperative – and often extremely gentle, tender, and loving. But these hours upon hours of peace and playfulness are punctuated by boisterous displays of dominance and, on occasion, acts of real, raw violence – violence between the very people we have dedicated our careers, and in many ways our whole lives, to caring for. For us caregivers, it amounts to a lot of worrying about a thing over which we have very little control.

Which brings me to this video. I’ve been wanting to share it for a while, for a couple of reasons. First, when a chimpanzee gets injured here at CSNW, people naturally ask who was fighting and why. Our answer is usually some form of “I don’t know” and “I don’t know.” It’s not because we aren’t paying attention, but rather because the nature of chimp fights make them hard to interpret at times. They can happen quickly with little warning, they rarely occur between only two individuals, and the individuals who get into a fight in the first place are not always the ones who come away injured. I’m grateful for the many books and documentaries that have demonstrated chimpanzees’ remarkable capacity for strategic aggression, but reality is often so much messier. Yes, chimps sometimes exhibit coalitionary aggression for the purpose of social status. But in addition to being Machiavellian, chimpanzees are also xenophobic, insecure, jealous, petty, anxious, and just plain cranky, and any and all of these can serve as the impetus to bite someone’s finger off.

Second, it’s important for people to get an accurate picture of how chimps live. We don’t want anyone to think that life for chimpanzees is nothing but eating, playing, and climbing trees. While we often discuss their injuries, we aren’t usually in a position to show the fights in which they occurred. As you can see, however, we can occasionally capture them on our security camera system.

But perhaps most importantly, I want to show you how they make up afterwards. Chimp societies wouldn’t hold together very long if the individuals within them didn’t have the capacity to reconcile, and that is the saving grace for both the chimpanzees themselves and our own ability to care for them. Because no matter how bad things get, they usually find a way to move forward together.

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So…the video. For what it’s worth, I’ve made it unlisted on YouTube so hopefully anyone watching will find it here and will also be reading this for context.

In the video, which is from December, you witness the beginning of the conflict as Willy B and Terry run out into the Greenhouse. Terry is upset, which you can see as he screams and splays himself out on the catwalk before running back inside for reassurance. The video picks up again in the Playroom, where Terry and Willy B face off momentarily by the door downstairs. The group congregates upstairs and Rayne then approaches Mave who is at the top of the tree structure. As Willy B moves in, possibly to protect Mave (though that is certainly open to interpretation), he comes face to face with Gordo. And that’s when all heck breaks loose. It took me several minutes of playing over and over in slow mo to piece together what was happening. For a time, I even falsely accused Rayne of a crime she didn’t commit. Sorry, Raynie!

We often differentiate between minor chimp fights and more serious ones based on whether or not they “ball up.” Balling up occurs when they grapple and bite, as opposed to chasing and hitting, at which point the caregivers can no longer tell who is who in real time. When chimps ball up, we know that we are going to have to look for injuries afterwards – checking ears and counting fingers and toes as they tend to their wounds. In this case, the chimps ball up for only a brief moment. They leap down to the floor through the fire hose vines and Willy B escapes up the stairs only to find his finger caught in Lucky’s mouth. He somehow manages to withdraw his finger intact and escapes through Playroom 3 to the Mezzanine where the screaming and reassurance-seeking continues. Fortunately, everyone made it out with only minor injuries.

At breakfast the next morning, Gordo – who was uninjured in the fight and whose “side,” you could say, came out on top – approached Willy B to reconcile. Breathy panting serves to express friendly intentions, and Gordo offers both his backside and his fingers and toes to Willy B. Isn’t it ironic that the way to make up after a fight in which you tried bite each other’s toes off is to place your toes in each other’s mouths again? While Mave and Rayne similarly reconcile, Gordo asks Willy B to follow him upstairs to groom. And once again, all is well.

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So that’s a chimp fight and the aftermath. Some are more serious, many less so. Some last for only a minute or two while others have gone on for as long as 20 minutes. The boys fight the boys, the girls fight the girls, and the boys and girls fight each other. It happens in new groups and in groups like the seven that have been together for 17 years. They are loud and fast and frequently complicated. Serious fights are relatively rare but they’re part of caring for chimps and while you never really get used to it, you do come to accept it. Running a tortoise sanctuary would certainly be better for the ol’ blood pressure. But if you love caring for chimps, as I do, you can’t pick and choose which parts you get to experience.

I’m sure this post raises more questions than it answers, so ask away and I’ll do my best to respond below! And my thanks to all of you for allowing us to explore a more serious and fraught topic from time to time. Hopefully it helps present a truer version of sanctuary life for both the chimps and the humans that care for them.

Slo Mo Dominance Display

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What’s more terrifying than a chimpanzee dominance display? A dominance display in slow motion.

The chimps have been crazy all day. Burrito can become very sexually aroused when the girls have their swellings, particularly when all three girls who cycle are in estrus at the same time. But because he was raised by humans (like most entertainment and research chimpanzees), he doesn’t exhibit normal sexual behavior. The result is a lot of tension, a lot of frustration, and a whole lot of chaos.

Jamie stepped out of the playroom during the afternoon to release some of that tension in the form of a dominance display. Displays are partly under conscious control and partly not. In this case, it seemed clear to me that Jamie climbed to the top of the platform with the intention of displaying. But at the same time she wasn’t fully in control of the display. We often liken displays in this way to sneezes. You know when you have to sneeze but you just can’t? And you can’t do anything else until the sensation either dissipates or culminates in a sneeze? That’s what displays can seem like for chimpanzees. Jamie stood on that platform for three minutes, rocking back and forth, softly pant hooting, and then repositioning and hooting some more, until she finally got everything out in a two-second display. When she was finished, she went about her business as if nothing had happened.

I think we’ll all be a lot happier in a few days when Burrito can start to focus on other things…