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Becoming a silverback: Leo's story

Posted by Stephanie Payne-Jacobs, gorilla keeper

EDITOR'S NOTE: Adult male gorillas are known as silverbacks because of the striking silver hair that grows across their back all the way down to their hips. This is not only a mark of maturity (silver hairs appear around 12 years-old), but a sign that one might be strong and determined enough to protect his troop. In most gorilla troops, the silverback is the center of attention. He is responsible for guarding the troop against outsiders, finding choice feeding sites and playing mediator between the other gorillas in the group. While silver hairs, larger canines and handsome red crowns (in Western lowland gorillas) are all visual characteristics of a mighty silverback, it is the personality and behavior of these males that determine if they will lead.

This is the story of how one such silverback, Leonel, has come into his own as a protector, leader and peacekeeperin part with a little help from a tiny, adorable baby called Yola.

While the gorilla keepers will tell you this is a story about two very special gorillas, we'd like to point out that it is also a story about an incredibly dedicated team of zoo keepers who are, without a doubt, world-class animal care experts and profoundly compassionate and determined humans. With that, here is gorilla keeper Stephanie Payne-Jacobs with Leo's story.

Leonel, photo by Dennis Dow/Woodland Park Zoo.
Yola successfully stole the show at Woodland Park Zoo this past summer, but the gorilla keepers are convinced that silverback Leo is the real star of the group. Since arriving at WPZ in the winter of 2008, he has become a respected leader in his family group, a position we were uncertain he could occupy upon his initial arrival.


Gorillas are social animals.  They benefit from each other’s company in the same ways that human families and groups do: they build alliances, provide companionship, create a sense of safety, but most importantly, they learn from one another. This is why it was so important for baby Yola to be around gorillas from birth and why it’s wonderful that she was integrated into her group at such a young age.

Leo was not afforded that opportunity. He was the first gorilla born at Gladys Porter Zoo in 1978, a time when the importance of encouraging a parent or surrogate reared infant were not fully understood. For safety concerns, Leo was moved out of his natal group shortly after birth for hand-rearing. 

Leo remained a solitary gorilla until age four, at which point he was transferred to the Los Angeles Zoo and introduced to a family group. Unfortunately, Leo never became a comfortable, cohesive member of that group. Records suggest that he seemed to lack the subtle vocal and physical cues that gorillas rely on for communicating with one another. After the LA Zoo, he lived at two other zoos, each with short-term and disruptive attempts at socialization with other gorillas.   

The Gorilla Species Survival Plan (a nationwide team of gorilla experts) was having a difficult time placing him in a new facility due to his reputation as being “socially challenged.”
Where should Leo live?

Leo by Dennis Dow/Woodland Park Zoo

When presented with the option of bringing 30 year old Leo to Woodland Park Zoo, the keepers agreed that we were up for the challenge.  Not only did we have a large number of females with varying temperaments, offering a variety of companion combinations for Leo, but we also had the space to accommodate such introductions. In addition, we had keepers who were experienced in successfully introducing non-reproductive males to females. It was decided that Leonel would come to Seattle.

Leo, front and center, with Yola and Nadiri in the background. Jeremy Dwyer-Lindgren

Leo’s first days at Woodland Park Zoo's gorilla unit were spent adjusting to his new surroundings, his new humans and the new routine. We knew that in order for him to feel comfortable meeting his new gorilla mates, he first had to know and trust the people he worked with. Once he had settled in, the process of introductions took place. These intros took many forms over the following months, as we gave the female gorillas and Leo the opportunity to get to know one another and see who clicked with whom.

The females were always given the choice to join Leo or not. Our job was to observe these introductions closely and note who was choosing to spend time with Leo, how the time was spent, and who was choosing to steer clear.

Nadiri, Yola, Leo and Akenji. Photo by Jeremy Dwyer-Lindgren/Woodland Park Zoo.
After a long and careful process, one that operated strictly on gorilla time, Leo, Nadiri and Akenji had finally shown us, through body postures, vocalizations and proximity to one another, that they were in fact, becoming a cohesive group.  Leo immediately took to Akenji, who is the more laid back, confident and playful. She was not intimidated by Leo’s size and would often engage him in play, or calmly sit near him. Nadiri seemed comfortable as well, but more as the third wheel rather than Leo’s first choice of companion.  

Over time, as this group became comfortably established, their roles became clear: as the silverback, Leo was the group’s (somewhat insouciant) leader, and as Leo’s favorite, Akenji became dominant over Nadiri whenever Leo was in the vicinity. When Leo was off resting in the distance, however, the terms of dominance (usually proximity to scattered food and desirable resting spots) between Nadiri and Akenji returned to an even playing field.

Nadiri, Akenji and Leo. Photo by Jeremy Dwyer-Lindgren/Woodland Park Zoo.

By 2015, Leo's gorilla group was an established family, but what would happen when Yola arrived?

In October 2015, the zoo was eagerly awaiting the birth of Nadiri's first-born (the father, Vip, lives with another group of females at the zoo). 


Nadiri herself was hand-raised for the first nine months and Akenji was hand-raised for the first six months (their mother was unable to care for them), and then there was Leo. We had no idea how any gorillas in the group would react to an infant. Nadiri had been around infants in her natal group and had witnessed maternal behavior, and Akenji had been around youngsters while she was a youngster herself, but it was Leo who was the real wild card. As far as we knew, Leo had never been in close proximity to an infant. His newly found comfort as a group’s silverback would once again be tested, as the dynamics were sure to shift once Nadiri had an infant and her protective maternal instincts would give her more reason to impose some dominant behaviors.

After Yola was born in November 2015, the dynamics between Akenji, Leo and Nadiri remained fairly unchanged throughout Yola’s first five months, as the baby established a relationship with her mother, Nadiri. This allowed Yola the necessary time to become more mobile and less dependent on her human caretakers. Nadiri’s presence in the group had to be somewhat fluid during this time, as separating her from Leo and Akenji for several hours a day was necessary in order to give mother and daughter the time they needed to bond. Being separated and reunited many times throughout the day became a normal part of their routine, but it did keep the group scratching their heads a bit as to what we were up to, and what was ahead.

During the Nadiri and Yola visits, Leo and Akenji would often be observed playing and laughing together, and we were a little concerned that their bonding time might push Nadiri to the outer fringe of the group. She was already the submissive female of the trio, and now she’d have a baby to protect once Yola was integrated. 

Little did we know, we had nothing to worry about. 

Yola (the little heartbreaker on the left) with mom, Nadiri. Photo by Jeremy Dwyer-Lindgren/Woodland Park Zoo.


It didn’t take long for keepers to notice that Leo would often situate himself in a place where he could watch Yola. Yola and her human caretaker would sit next to Leo while he was fed or engaged with another keeper, allowing Yola to gain confidence in his proximity. It was during this time that Leo showed further interest in Yola by soliciting touch through the mesh and content grunting ("Hello" in Gorilla) whenever contact was made. Leo was always calm and Yola picked up on this, establishing from the very beginning, a positive and respectful relationship with one another.

Once Nadiri and Yola were spending the evenings together, we began our discussion of whom from the group we should integrate next. Before any observations of the groups reactions to Yola had been made, we had considered Akenji as the a possible first step, as she and Nadiri share a history together, and typically, females create a strong bond to unite them and keep the larger silverback in check, but Leo’s behavior towards Yola led us to suspect he may be the better choice (despite his lack of infant experience).

Where Leo’s approach to Yola was always positive and calm, Akenji’s behavior was just the oppositeshe seemed jealous of the baby, often displaying towards Yola, trying to poke her with sticks and threat grunting towards her.  Fourteen year-old Akenji, Nadiri’s sister, has always been the youngest member of any group she has lived in and just like any baby of any family, she is a bit spoiled. Akenji was having a difficult time being usurped by Yola.

One of our concerns prior to introducing Leo, was Nadiri’s extremely relaxed parenting style. While the visits between Nadiri and Yola had been going wellNadiri always being gentle with Yolawe still had not observed her pick Yola up and carry her. This was acceptable when it was just the two of them, as Yola would just follow Naidiri, but we knew it wouldn’t be enough for Yola to just amble after Nadiri once Akenji was added to the mix. We needed to see some protective mama instincts kick in, which had so far been missing from the equation.


In preparation for the physical introduction with Leo, we began by inviting Leo into a shared room with Nadiri and Yola, though separated by wire mesh. This allowed Nadiri to adjust to Leo being allowed access to an area that she and Yola usually had to themselves. As Leo was given access to the back half of a room, Nadiri and Yola were given access to the front half of that room, as well as several adjacent rooms where Nadiri could move away from Leo if she felt uncomfortable. Keepers were beyond excited and close to tears when, after giving Leo access to the back room, Nadiri quickly picked Yola up and carried her out of Leo’s sight. It was the first time Nadiri had picked her up, and the keepers could barely contain themselves upon seeing this. Although Leo had been completely calm and appropriate, having him in this new proximity and configuration made Nadiri just cautious enough to exhibit protective instincts towards Yolaproving that she indeed would take care of Yola when faced with an uncertain situation.

The second day, we slowly opened the door and allowed Leo to come into the same space with Nadiri and Yola. Leo was a bit nervous, so he made a very appropriate display past Nadiri and Yola and then went to sit on his favorite bed and observe from there. Nadiri again showed protective behavior by picking Yola up and carrying her from room to room.

After 12 days, Nadiri, Yola and Leo seemed comfortable with one another, respecting personal space, content grunting during transitions, eating near one another, passing closely by one another, and, most importantly, agreeing to participate in the introductions each day.  So far, the introduction had not only shown that Nadiri had protective instincts towards Yola, but that Leo might share those instincts as well. For these reasons, we soon felt it was a safe time to bring Akenji into the mix.

Yola testing out her swinging skills. Photo by Jeremy Dwyer-Lindgren/Woodland Park Zoo.


It was no surprise that the intros became a bit more animated once Akenji joined. Each morning, after several initial displays, Akenji would sit down a few feet from Nadiri and Yola, occasionally trying to touch Yola and smell her. Whenever Akenji did anything to upset or scare Yola, Leo would immediately reprimand Akenji, and she soon learned she had to behave. Keepers were happily surprised to see Leo immediately show appropriate silverback behavior and stand up for Nadiri and Yola. Nadiri quickly realized that Leo was the silverback protector. It is natural for a new gorilla mom and baby to sit in closer proximity to the silverback, and for the silverback to allow this to occur.

Leo's role as silverback in keeping peace among the group further compliments his transformation into a true member of his own gorilla family.

It has been interesting to watch Leo and Nadiri’s natural instincts kick in and sync together. It has also been wonderful to witness Leo and Nadiri’s relationship evolve in the presence of Yola. Whereas Nadiri had always been on the periphery of Leo and Akenji’s relationship, she now stays in close proximity to Leo. Akenji and Leo still play and enjoy each other’s company, but he now recognizes his new role as silverbackprotecting Yola.

Nadiri and Yola on a summer day, photo by Jeremy Dwyer-Lindgren/Woodland Park Zoo


On Sunday, November 20, Yola will turn one. She is proving to be a well adjusted gorilla, capable of interpreting appropriate gorilla body language and subtle vocalizations. She still steers clear of her auntie Akenji, but we’re confident that they will have a wonderful and energetic relationship once Yola is a bit bigger and more confident.

Leo and Yola’s relationship couldn’t be better. It’s not uncharacteristic of silverbacks to be great dads; playing with their kids and even carrying them around from time to time, but Leo’s early experiences could have easily hindered his ability to deal well with an infant. Instead, he has proven invaluable to the group’s success. Yola really seems to find comfort in his presence, and will play with abandon near him, assured in the fact that she’s safe to do so.

It will be interesting to watch Leo and Yola’s relationship grow as she gets older. Just last week, as keepers called Leo inside for the night, we were surprised to see him enter from the yard with Yola leading the way. This was a first, as she has always stuck by Nadiri during transitions. Akenji was right behind Leo (as she usually is during this transition) and when Yola saw this, she immediately grabbed onto Leos’s leg. Leo allowed this to happen, and let her hitch a ride through the threshold of the door, gently shaking her off once they were inside. Yola didn’t appreciate this, especially in such close proximity to Akenji, and screeched, causing mom, Nadiri, to run in and calm her and for Akenji to quickly leave the area, lest it cause an unwanted conflict right before dinner. This timeline of events was a reminder of how far they have all come: Yola was comfortable enough to run to Leo for comfort and safety and Leo allowed her to do so, Nadiri still came when Yola called, and Akenji knew better than to get involved.

Yola in her element. Photo by Jeremy Dwyer-Lindgren/Woodland Park Zoo
We are so thankful for these wonderful gorillas whom we are privileged to know and share our days with, and our hope is that zoo guests feel the same. The gorillas are here to teach us, encourage us and inspire us to care about the importance and beauty of their existence among us in this world. The lives of their wild counterparts depend on this understanding.  

The three gorilla groups at Woodland Park Zoo are compelling ambassadors for the critically endangered gorillas in Africa threatened with extinction. Woodland Park Zoo supports conservation efforts for the western lowland gorilla through the MbeliBai Study, one of the zoo’s Partners for Wildlife. The study researches the social organization and behaviors of more than 450 lowland gorillas living in the southwest of Nouabale-Ndoki National Park, Republic of Congo. The data collected enables scientists to assess the vulnerability of populations to habitat threats, providing the groundwork for successful conservation strategies.

Visit Yola, Leo, Nadiri and Akenji at 12:30 p.m. daily and remember to #GrowWithYola to share your favorite memories of this little gorilla and her incredible family. 


Julie said…
Thank you so much for this. It has been fun to watch them when they are in the front of the exhibit but these additional stories make my understanding of the dynamics richer. Congratulations to the keepers for doing such an amazing job working this to a successful completion.
Anonymous said…
Thank you for sharing Leo's story what a joy to see him grow into his natural role with your help!
Unknown said…
Kudos and thanks to everyone who helped Leonel become the silverback he deserves to be. The SSP is to be congratulated for giving each and every gorilla in their care the patience and individual attention to make their lives as good as captivity allows. While male gorillas are being castrated under the EEP (World vs N. America gorilla management) I'm proud to see this great example of the devotion to *all* gorillas by Woodland Park et al.
Unknown said…
As a retired gorilla keeper from Toronto Zoo I really enjoyed reading this story. Working with these Wonderful animals is a great privilege and takes time & patience, both of which you have demonstrated in abundance.Congratulations! Marilyn Cole
Emily said…
Thank you so much for sharing these stories! What a great way to inform natural teaching moments with our children when visiting the zoo. We just love visiting Yola, and now have an even deeper appreciation for all the thought and care that has gone into making WPZ her home!
Zoo de Vienne said…
Oh my god Yola is so cute *o*, it's hard to believe that she has only 12 days old !
Unknown said…
So happy to hear Leo is doing great. Fun Fact: he was named after my great grand father Leonel Garza, who was president of Gladys Porter Zoo at the time Leo was born. We even have a picture of him and Leo here. Greetings from Texas
Unknown said…
So happy to hear that Leo is doing great! Fun Fact: he was actually named after my great grand father Leonel Garza, who was president of the Gladys Porter Zoo at the time Leo was born. We even have a picture of hi and Leo here. Greetings from Texas.