Grantee Spotlight: Joel Bray

Joel Bray was awarded a Leakey Foundation Research Grant during our spring 2017 cycle for his project entitled “Social relationships in male chimpanzees:  Form, function, and development.”

Joel Bra

Variation is the raw material of natural selection, yet we struggle to explain why individuals vary in complex traits such as social behavior. Why are some adult male chimpanzees highly gregarious and others less so? Why do some male pairs form strong and durable social bonds while others do not?
In my dissertation, I am investigating one source of variation: the role of development and early social experiences in male chimpanzee social behavior. During infancy and juvenility, chimpanzee mothers mediate their offspring’s social experiences by choosing which community members to travel with and for how long. I am interested in how this social exposure affects an individual’s social relationships, rank, and fitness later in life.

I focus on male chimpanzees for two reasons. Unlike females, all male chimpanzees remain in the community in which they were born; thus, early life social experiences may directly influence whom individuals interact with later in life. Additionally, male chimpanzees are more gregarious than females; social relationships are therefore likely to have a greater impact on male fitness.

Where am I? I’m currently living in Gombe National Park, Tanzania, where Jane Goodall conducted her pioneering and groundbreaking research. My fieldwork here will address questions such as when and how partner preferences emerge during development. Meanwhile, I am analyzing 56 years of long-term behavioral records at Gombe to examine social bonds over the course of individual lifetimes. In other words, I will compare observations from a male’s childhood to his behavior as an adult.

I anticipate that my dissertation will help to explain individual variation in adult male chimpanzee social behavior. Furthermore, although the natural history of adult chimpanzees is well understood, basic facts of chimpanzee development remain unknown. Thus, I hope that my fieldwork will also stimulate research on chimpanzee social development by helping people ask more detailed questions and generate more refined hypotheses.

Where does this research fit within the larger story of human origins? Chimpanzees are one of our two closest living relatives and face social pressures similar to those of early hominins. Chimpanzees therefore provide clues about our last common ancestor and what changes occurred in the hominin lineage.

From the Field: Kristin Sabbi, Uganda

Kristin Sabbi is a doctoral candidate at the University of New Mexico. She was awarded a Leakey Foundation Research Grant during our spring 2016 cycle. Click here to read a brief summary of her project. Here she updates us on her third field season in Kibale National Park, Uganda.

This year marks my third and final dissertation data collection season, thanks to The Leakey Foundation. Over the last two field seasons, in 2015 and 2016, the chimpanzees at Kanyawara have been very good to me. As I’ve followed their infants and juveniles, I’ve witnessed some pretty incredible behaviors ranging from ultra-gentle males to unique tool use to once-in-a-lifetime chance events (both happy and sad). In 2015, I saw my first nursery play group of about a half dozen adult females and their offspring. I also followed an infant as an adult male carried her on his belly for a good 100m just to set her down and tickle her for almost an hour. In 2016, we were there to witness characterize how the rest of the group responded to both births and the falling death of a two-year old. But this year, brought one of the most amazing phenomenon I might ever be so lucky to witness.

But first, a bit about chimpanzees to help explain how incredible this summer was. Chimpanzees exhibit what we call a “fission-fusion” social system whereby the larger community breaks apart into smaller subgroups and ranges together throughout the day. For instance, our community has just under 60 chimpanzees, but you might find all kinds of variation among subgroups in a day. One chimp might feed in a tree on their own, or one mother traveling with just her offspring, or a small band of five or six males grooming on the trail, up to a mixed party doing any of the above! On average, the groups that I’ve followed during my data collection have averaged seven to 12 members (including infants and juveniles). Individual membership in these parties can be highly fluid and flexible throughout the day such that one chimp might range with a number of different parties between dawn and dusk. This system is a great one for a study like mine because chimpanzee mothers’ ranging preferences can lead their infants to have very different individual early life social experiences even though they are a part of the same community. However, it can also be difficult to make sure that I find and follow each infant and juvenile equally.

The academic “summer” term is always a great time to follow chimpanzees at Kanyawara because the chimps’ favorite food, Uvariopsis congensis, brings large, loud groups of them together. This is especially great for me not only because I get to spread out my follow time but also because I can capitalize on some rare opportunities to see more peripheral chimpanzees interacting in these large groups. As May rounded the corner, I was already excited for the 2017 Uvariopsis season. But I was completely unprepared for what we got!

It started out just like it had in previous years, a few fruits ripening in a few groves here and there, mostly in the center of the territory. A few of our more central females and their offspring started traveling with the core group of high ranking males. As more and more trees ripened, more chimps joined the foraging party, following the ripening crop further and further from the center of the territory. Each day fewer and fewer of them split off to forage on their own until, suddenly, one day in late May we realized that all but one of the Kanyawara chimps was here, foraging, and traveling, and sleeping together. Counter to their general proclivities, the community had effectively stopped fissioning and was spending their days traveling as a huge cohesive unit. We followed them like this for days, amazed at what we were seeing and the joy of seeing it. And then it just kept on going like that for weeks!


Of course, the best parts for me weren’t necessarily the foraging or traveling but the huge increase in social time! With so much food to go around, rates of interactions, both aggressive and affiliative, soared. While the almost-adult males ramped up their physical displays, vying for dominance, they played with each other and other group members just as often. Mothers and their offspring clumped together to play and groom. In fact, some moms were feeling so social that they played with each other to the exclusion of their infants! As play rates and grooming shot through the roof, so did my data collection. By the time that the Uvariopsis dwindled and the group finally began to fission again in mid-July, I had already captured multiple follows of every single infant and juvenile while they ranged, and played, with the whole community. Talk about wrapping things up on a high note!

It’s not necessarily unique to see so many chimps together, especially among the very large communities like Ngogo (230+ members). But to see such a large proportion of Kanyawara together and spending so much time traveling and playing with each other was truly exceptional. It could not have been a more perfect summer for data collection, and it is an experience I will cherish forever.

Utah at play, all day.

Grantee Spotlight: Laura Abondano

We are excited to begin sharing the work of our spring 2017 grantees! Here we have Laura Abondano, PhD candidate from the University of Texas at Austin, who was awarded a Leakey Foundation Research Grant for her project entitled “Mating strategies of female lowland woolly monkeys in Amazonian Ecuador.”

Meet Grulla, an adult female woolly monkey, and her recently born baby girl, Grizzly. Grizzly is one of the infants that was born in the 2017 woolly monkey birthing season at our study site in the Ecuadorian Amazon. During the 2016 mating season, Grulla was perhaps the female that we saw engaging most often in sexual behaviors, and we saw her mate with almost every non-juvenile male in the group! Now, seven and a half months later (which is the average gestation period for woolly monkeys), she has given birth to this baby girl.

Grulla, a female woolly monkey, with her infant who was born during the 2017 birthing season.

Woolly monkey females are very active at soliciting males for copulation, and they do so by either presenting their genitals to a male, touching a male’s genitals, or by making a teeth chattering expression. Often these behaviors lead to the male mounting the female. What is really interesting is that female woolly monkeys, like Grulla, will display these solicitation behaviors to almost every adult male (and sometimes even subadult males) in the group. However, despite the fact that females copulate with multiple males in the group during a single ovulation cycle, not all males father babies equally. In fact, larger and presumably older adult males are the ones that sire most of the infants in our study groups. This discrepancy between the number of female mating partners and actual sires has caused us to wonder if woolly monkey females employ a strategy similar to that reported in some studies of women in which they become more selective of their mates during ovulation but still engage in sexual behaviors with other types of males outside their peak fertility period. By choosing to mate with larger males when they are they are ovulating but still copulating with other males outside their fertile period, woolly monkey females may be able to confuse paternity among the males and increase their chances of obtaining potential benefits (e.g., food sharing, protection, social interactions) from all males in the group.

From left to right: Laura Abondano (PhD candidate at the University of Texas at Austin), Savannah Perez (University of California at Santa Barbara), and David Mantilla (Universidad Central de Quito) following woolly monkeys at the Tiputini Biodiversity Station, Ecuador.

During this 2017 field season with the help of two field assistants, I will be following female woolly monkeys that are sexually receptive, as well as females, like Grulla, that became pregnant during the 2016 mating season. Although Grulla is now no longer copulating, we are interested in seeing how males interact with her infant. If Grulla was successful at confusing Grizzly’s paternity last year, perhaps we will see multiple males engaging in affiliative behaviors with the infant. We hope to continue working with these woolly monkeys to determine whether male-infant interactions represent possible paternal affiliation or if males are engaging in social behaviors with infants to possibly influence females’ mate choice decisions and increase the male’s chances of mating with those infants’ mothers in the future.

Laura Abondano searching for radiocollared woolly monkeys.

Read more about Laura’s work and experiences! She mentioned that we might want to share the blog that she and Leakey Foundation grantee Kelsey Ellis have created.  This would “highlight that our work on the woolly monkeys at the Tiputini Biodiversity Station has been thanks to the funds that the Leakey Foundation has awarded to both Kelsey Ellis and myself.” Click here!

A Giant Advantage: Baseball in Our Bones

On November 1st, The Leakey Foundation and the Bay Area Science Festival will be presenting our next Science Speakeasy:  Fake or Fact, featuring Todd Disotell. Join us for an evening separating the factual from the fantastical! To learn more, click here

For you to get a little taste of what it’s like at a Science Speakeasy, guest blogger Rebecca O’Neill (see bio below) shares her impressions of our July 12th installment, Science Speakeasy:  A Giant Advantage:  Baseball in Our Bones.

Dr. Nathan Young on stage at Science Speakeasy

Evolution requires two things: variation and selection — variation meaning differing characteristics across a population and selection meaning individuals with specific differences having greater fitness (i.e. ability to survive and produce offspring).

Sports are an ancient human invention but one thing is consistent across the world and through time – the games require the expression of physical and mental prowess of the players to the point that there are clear winners and losers, just like in evolution.

A recent Science Speakeasy lecture I attended dove into how our body has evolved to play one of our nation’s favorite sports: baseball. The talk focused on our ability to throw – clearly a key component of the game.

Evolutionary biologist Dr. Nathan Young started by explaining how the human body is uniquely set up to throw well. For example, our longer spine compared to that of a chimpanzee enables more flexibility, meaning we can twist our upper body in relation to our lower and achieve more torque (rotational force).

Our elbows can extend in certain angles, which he showed in some impressive slow motion videos (and which can lead to problems, as the next speaker explained). Our longer thumbs and shorter fingers enable us to have a precision grip, so we can deliver a fastball, curveball, or other specific throws.

What’s most impressive though is our shoulder. Dr. Young showed us that our scapula (shoulder blade) is shaped so that shoulder muscles are more lateral, while a chimpanzee’s scapula is more upright – for hanging from trees. Our shoulder is essentially a catapult, with rotation leading to a buildup of energy that is then powerfully released in the throw. In fact, the rotation of our shoulder is the fastest in our bodies. So, we are excellent throwers while chimpanzees, though strong in many ways, are terrible throwers in comparison.

Ken Akizuki

San Francisco Giants’ official orthopedic surgeon Dr. Ken Akizuki then stepped onto the stage to highlight that our ability to throw evolved from our hunting lifestyle, but if we do too much of it, it can lead to problems. “Dead Arm Syndrome” is common among professional baseball players. Symptoms include pain and inability to achieve a consistent throw. The syndrome is a result of damage to the shoulder from overexertion and repetition. “Tommy John” surgery addresses injuries in the elbow.

The fact that these types of injuries and surgeries are increasing demonstrates that players are pushing themselves harder and harder. Dr. Akizuki explained that the average speed of a baseball is actually going up, with speeds of up to 95 miles per hour!

Sports teams are selecting for the extremes in abilities, whether it’s throwing, or running or jumping. Elite athletes are shaping their bodies according to what makes a winner in that particular game. The speed of a baseball throw is likely increasing because athletes are practicing more, from a younger age.

Though evolution works much more slowly than the pace of change we are seeing in the baseball throwing speed, we are possibly influencing our future evolution through participating in athletic activities. Only time will tell what effect sports will have on humankind, but in the meantime, it’s darn good fun so:  Play Ball!

(L to R) Nathan Young, Arielle Johnson (Host), and Ken Akizuki

About Rebecca O’Neill

I am a lifelong learner who is a passionate advocate for science and the human capacity for innovation. I have a bachelor’s degree in biology from Oxford University and a master’s degree in environmental science from Imperial College London. I have worked in a variety of nonprofit, media and business roles to promote environmental conservation. I currently live in Oakland, California, and work at SustainAbility, a hybrid think tank and strategic advisory firm working to catalyze business leadership on sustainability.

Charles Darwin has been a hero of mine for as long as I can remember. Evolution is one of the most important scientific theories that humans have discovered. I believe that The Leakey Foundation’s mission is a crucial one – we need to understand how we have evolved in order to make better decisions for ourselves, our society and our planet, both now and in the future.





From the Field: Cayo Santiago, Puerto Rico

Erica Dunayer was awarded a Leakey Foundation Research Grant during our spring 2016 cycle. You may read a brief description of her project by clicking here. Here she has provided a post-hurricane update from Cayo Santiago, Puerto Rico. 

Erica Dunayer collecting data on Cayo. You can see how lush and green vegetation is and how rich the sea is behind it all prior to Maria. Photo Credit: Stephanie Munro

I’ve spent the last year using my funds from The Leakey Foundation to support my dissertation research on the famed “Monkey Island” located on Cayo Santiago—a small island off the coast of Puerto Rico. My days were spent observing the intricate social interactions of 50 rhesus macaques. (The island is home to more than 1000 monkeys.) But my afternoons were spent getting to know the people living in the Punta Santiago community, which is the small fishing village that has housed the researchers and the Cayo Santiago staff for almost 80 years.

With my Leakey Foundation funds, I am investigating how mothers negotiate access of their infants to seemingly ardent, though not necessarily trustworthy, admirers. In rhesus, non-mothers show strong attractions to touch, handle, embrace, and groom infants that are not their own, and often gain favor with mothers by first grooming them. Importantly, previous research has shown that the number of available infants dictates the duration of grooming provided to mothers, resulting in a supply and demand relationship. It is our hope that studying the mechanisms constraining these exchanges in rhesus may help elucidate our understanding of the complex economic exchanges seen in humans.

Cayo Santiago after Maria. Photo credit: Angelina Ruiz Lambides

September proved to be a crucial month for my project. September is the peak of the birth season on Cayo, so this should have been the height of my data collection. Unfortunately on September 20 Puerto Rico was devastated by Hurricane Maria, with Cayo Santiago receiving a direct hit from the Category 4 storm. Luckily, a substantial amount of infant handling data for the project were already collected, and we are optimistic that we can still address the questions outlined in the original proposal.

The good news is that monkeys in all social groups on Cayo Santiago survived. However, the resilient monkeys, including the new mothers and their babies, now face further problems. The infrastructure providing fresh water on Cayo Santiago was destroyed with the vegetation providing food and shade to the monkeys completely decimated.

Even though they have already lost so much (including their own houses in some of these cases), the Cayo staff have already returned to Cayo to start rebuilding and helping the monkeys!! This picture was taken on Cayo post Maria. Photo credit:
Angelina Luiz Rambides

The situation for the people of Punta Santiago is just as dire. Prior to the storm, there was a mandatory evacuation for the community. With no place to go, Cayo Santiago staff members living outside of Punta Santiago opened their homes to the displaced researchers. Even outside of Punta Santiago, the situation was harrowing. My research team and I woke around 5 AM with water already up to our calves. Apparently our new location couldn’t provide a complete respite from the storm. After a portion of our roof collapsed, we spent the next several hours funneling water out of the house until it became “safe” enough to try to temporarily mend the roof. I was fortunate enough to fare better than most, especially the members of our beloved Punta Santiago. Most of the community have lost their homes and all of their personal belongings, and like the monkeys on Cayo Santiago, are in desperate need of access to clean drinking water and food.

Cayo Santiago staff arrive to the island post Maria, with several monkeys alive and waiting for them! Photo credit: Bonn Aure

The damage to both Cayo Santiago and Punta Santiago was catastrophic; however, I remain optimistic. My time in Punta Santiago has taught me that the people of Puerto Rico are some of the kindest, hardest working, and most generous people I will ever know. Although their community may be temporarily broken, their resilient spirit, buttressed by relief efforts organized by current Cayo Santiago researchers from various institutions (many who are past and present Leakey Foundation grantees), will no doubt allow for the rebuilding of both the research facility and the community at large.

Relief efforts for the Punta Santiago community and the Cayo Santiago research station are currently being organized by the scientists at the University at Buffalo, University of Exeter, New York University, University of Pennsylvania, University of Michigan, Yale University, University of Washington, the University of Puerto Rico and the Caribbean Primate Research Center (in addition to many others).

To donate to the members of the Cayo Santiago staff and Punta Santiago community, click here. (

To donate to help the monkeys and restore the biological field station of Cayo Santiago, click here. (

The effort to rebuild Cayo infrastructure is underway! Photo credit: Angelina Luiz Rambides