May 13, 2021: Raven's Milestones and Development

Baby Raven is 6-1/2 months old! The primate care team shares what she's up to and some milestones of her growth and development. Enjoy this photo dump of pictures from this spring!

  • All eight of her incisors have come in.
  • While still primarily nursing, she loves applesauce! She also likes to nibble on pieces of the adults' diet, like romaine lettuce or cooked squash.
  • She has mastered climbing on the small fire hose but can't quite figure out all the climbing structures yet or is still too small for some of them. Caregivers have been adding smaller climbing structures to the habitat so she can continue to practice her climbing and swinging skills!
  • She travels around clinging to her mom's belly, although she will crawl or climb short distances away from her to explore.
  • She's very interested in all things! She is often seen reaching for plants, bark, wood wool, blankets, and other enriching items provided to the chimpanzees. Any new item is a fun toy to explore.
  • She's quickly mastering chimpanzee communication. She mimics the adults' vocalizations, facial expressions and body language and can easily communicate to others when she is interested in playing or in need of reassurance.
  • She loves to play! She always finds a willing playmate within the group to engage in a quick game of tickle with her.

The chimpanzee family group can be seen in their outdoor home at Donn & Marilyn Lipton Fragile Forest, weather and conditions permitting. Be patient in looking for the little one, as she's sometimes hard to see when being carried by her mom.

Chimpanzees are critically endangered in their native Africa. Populations are perilously low due to several factors, including deforestation, disease and the bushmeat crisis (illegally sold meat from wild animals). The Zoo is dedicated to caring for chimpanzees both at the Zoo and through the Saint Louis Zoo WildCare Institute Center for the Conservation of Congo Apes, which works with partners to help conserve chimpanzees and western lowland gorillas in their natural environments.

Click pictures to view slide show.

January 11: Raven Meets the Group

Over the last month, part of Raven’s early development as a young chimpanzee has included meeting and beginning to establish relationships and bonds with all the chimpanzees in the group. Still quite small and reliant on her mother, all of these interactions have occurred under Utamu’s close guidance as Raven clings to her. Luckily for Raven, Utamu is very social and high-ranking in the group, and she has strong positive relationships with the other chimpanzees. So Raven is already often in the center of social interactions and of interest to all the chimpanzees, even though she is only a couple months old. While always protective and keeping Raven secure on her hip or belly, Utamu has been letting other chimpanzees gently groom Raven. Even though she is quite small, the other chimpanzees have shown a lot of interest in interacting with Raven like they would with any other member of their family. It’s not uncommon to see chimpanzees near Utamu, greeting Raven with head nods to get her attention.

Since she went into labor with Raven, Utamu has had the continuous support of two older females in the group: her mother Rosebud and Beauty. They have been the core group with Utamu to help her navigate her new role as a mother. As Utamu bonded with Raven those initial weeks, the other younger females were introduced and spent some time getting to know the new baby. The last members of her family whom Raven needed to meet were the males.

As the dominant male, Hugo is pretty protective of the group, and so he was introduced first to the infant group to give him a chance to bond with Raven and Utamu and to prevent any jealousy toward the other males. Hugo was very happy to see Utamu and the new member of the troop, Raven. This was evident by his relaxed, droopy lip and head wobbles, which are behaviors common for him in play. Throughout the introduction, lots of grooming and playing were observed between him and Utamu as well as with the other females. Next, Kijana was added to the group, followed by Jimiyu. Both males were seen embracing Utamu as well as engaging in play sessions. During all the introductions, the chimpanzees were observed gazing intently and with interest at Raven, but they followed Utamu’s cues and waited until she was comfortable to groom or interact with Raven. For Raven’s part, she was observed peeking out from her mother’s hip, watching all the excitement and new friends. 

We are very excited for Raven’s integration in the chimpanzee group and look forward to watching her continue to establish these social relationships with her extended family as she grows up.

December 20: Happy Birthday Utamu

On Sunday, December 20, chimpanzee Utamu celebrated her 19th birthday. The new mother and her newborn daughter, Raven, continue to bond behind the scenes in a private maternity area. Both mother and baby are doing well. A public debut date is not known at this time. Happy Birthday, Utamu!

December 1: Checking in with Mom and Baby

For those of you who have followed Utamu’s path to motherhood, you know about the preparation and training that have gone into helping Utamu prepare to be successful as a new mother.  You may also remember the important role the other chimpanzees play in this process, especially her own mother, Rosebud.

The new baby, named Raven by her keepers, was born around 3:30 a.m. on Wednesday, October 28, 2020, with the primate care team monitoring the birth over cameras. Rosebud was even more closely monitoring her daughter, and then new granddaughter, throughout labor and birth, waking up and leaving her own comfy nest to check and groom them both.

As a first-time mother, Utamu faced some new challenges. While very gentle and protective over her new little one, she initially struggled to figure out what the infant was doing and how to get her into the right position to nurse. The primate care team has established a very strong relationship with Utamu and worked with her to learn this new skill of how to nurse her infant.

Unfortunately, it is not uncommon for new mothers and babies – of many species – to have nursing not come naturally. With not having successfully nursed, and Utamu also showing decreased activity and interest in food, the veterinary and primate care teams performed wellness exams on both animals, and placed the infant on Utamu in nursing position to help her learn where to go and what to do. To help mom and baby have the best chance to thrive, the decision was made to care for Raven for a few days to give her the nutrition needed to get strong and healthy, as well as to give Utamu a chance to rest and rebuild her strength. 

During this time, the baby was near Utamu during the day so she could continue to bond and keep a close eye on her. The primate care team also used this time to continue to work with Utamu on maternal behaviors, such as getting her infant into nursing position or allowing caregivers to supplement her infant with a bottle. 

After a few days, when both had gotten a chance to rest and regain their appetites, Raven was reunited with Utamu. She quickly and gently picked up her daughter and started grooming her, showing the same care and attention she had after the baby’s birth. The primate care team continued to monitor them and worked with Utamu on how to get the infant into position to nurse. This was a very critical time. If Utamu did not learn how to nurse her baby, there was the possibility Raven would have to be hand-raised, which is never the preference compared to mother-rearing.

Happily, together Utamu and Raven were able to figure out how to overcome this new challenge of motherhood and the primate care team started to see nursing, which then became more regular and consistent. With her new understanding of how to nurse her infant, Utamu has continued to be an excellent and caring mother. There are still new challenges ahead as Utamu continues to navigate her new role as a mother but we are overjoyed with how she and Raven have progressed so far.

Utamu and her baby will stay in a private maternity area for some time to allow them to continue to strengthen their bond. A public debut date is not known at this time. Zoo guests may see other members of the chimpanzee troop in the outdoor Donn and Marilyn Lipton Fragile Forest habitats, weather permitting.

It’s a girl!

Chimpanzee Utamu gave birth to a yet-to-be-named female baby around 3:30 a.m. yesterday, October 28, 2020, at Jungle of the Apes. 

The baby appears to be healthy and is clinging to mom well, according to the Zoo’s primate care team and veterinarians. The team will watch the mother and infant closely during the coming days and weeks, monitoring for nursing and observing the behavior of Utamu and the baby. 

Utamu and her baby will stay in a private maternity area for some time to allow them to continue to strengthen their bond. A public debut date is not known at this time. Zoo guests may see other members of the chimpanzee troop in the outdoor habitats, weather permitting.

Check out this video of Utamu and her baby courtesy of Jungle of the Apes keepers.

Read more at: Chimpanzee Birth

Check out Utamu's Path to Motherhood from the beginning. 

August 26: Utamu's Expecting

 We are excited to announce that Utamu, an 18-year-old chimpanzee at the Saint Louis Zoo, is pregnant and due to give birth this fall at Jungle of the Apes. The pregnancy is based on a breeding recommendation by the Association of Zoos and Aquariums Chimpanzee Species Survival Plan. 

“The primate team working with our chimpanzee troop is very experienced and highly skilled. The strong, trusting relationships they have built with the chimps is integral in providing the high level of care and training to prepare for this important pending birth,” said Heidi Hellmuth, Curator of Primates, Saint Louis Zoo. 
Click here for more info. 

Photos: Ethan Riepl 

September 2: Getting to know Utamu

Utamu was born on December 20, 2001, in Florida at the Miami Metrozoo (now called Zoo Miami). She first arrived at the Saint Louis Zoo as a juvenile chimpanzee in early 2007 along with her mother Rosebud. She has benefited greatly from Rosebud’s social personality and popularity with the other chimpanzees, as they both easily integrated in the group. Rosebud and Utamu are often found in the middle of any social interaction such as playing or grooming. Even though Utamu is older now, she continues to share a strong bond with her mother Rosebud and they support each other within the group. Growing up with her mother always watching out for her and often being the center of social interactions, she is a very confident, social and respected chimpanzee within the group.
Utamu has a very distinctive ‘voice’. Her laugh and food vocalizations can easily be picked out by keepers from the rest of the chimpanzees. Since she is so well liked, she is good at getting what she wants, especially food. Even when she was little, she could usually get someone such as Beauty, a female in her late 40s, and Jimiyu , a 28-year-old male, to share food by food peering, which is when a chimpanzee gets really close (within inches) of another chimp who is eating something delicious and just stares. This probably wouldn’t work as well for us humans as it does for Utamu, though!
When not relaxing or eating, Utamu is often seen playing with her two close pals, 18-year-old Tammy and 22-year-old Bakhari, two female chimpanzees. These three are close in age and all enjoy a good play-chase or wrestling session complete with tickling. As she has progressed in her pregnancy, Utamu is usually more inclined to relax with her mother and Beauty than engage in rambunctious play, but her friends can often still get her to engage in more laid-back tickle sessions.
Utamu’s favorite locations are hanging out high on the habitat hammocks or relaxing in the viewing shelter windows under the air vents with the other female chimps. First thing in the morning, you can usually spot her grooming and foraging with the rest of the chimpanzee group on the large rock overhang in the center of their habitat.

September 9: Discovering a pregnancy

So just how did the primate care team find out that Utamu was pregnant you might wonder?

It might be helpful to begin with a little background information on chimpanzee female reproductive cycles.

Chimpanzees have about a 36-day reproductive cycle. The primate care team is able to track this cycle for all the female chimpanzees as part of our daily husbandry monitoring. When a female is ovulating or “can become pregnant,” she develops what is called an estrus swelling. Her behind swells up looking a little like a small inflated pink balloon. For the rest of her cycle, this area is deflated and has loose pink skin. Female chimpanzees also menstruate during their cycle. So if one of these events is missing or late, it can often be the first indication of a potential pregnancy to the primate care team.

Utamu with full estrus swelling.

Rosebud with no estrus swelling.

How do we confirm a chimpanzee pregnancy?

We use an at home pregnancy test, the exact same type that you would use to confirm a pregnancy for a human! Utamu is trained to urinate when asked and this can then be collected and applied to a home pregnancy test.

We also have a secondary method to confirm pregnancy:

You might not know this but the Saint Louis Zoo has its own endocrinologist, Corinne Kozlowski, Ph.D., and an endocrinology laboratory. One way to have a secondary verification of a chimpanzee pregnancy is to compare progesterone levels of a suspected pregnant chimpanzee to progesterone levels of a non-pregnant female chimpanzee. Progesterone levels rise during pregnancy. The care team is able to submit fecal samples from the chimpanzees collected during daily cleaning to the lab where Dr. Kozlowski can evaluate them.

Continue to follow Utamu: Path to Motherhood to learn more about Utamu’s pregnancy and the work being done by Saint Louis Zoo staff in preparation for the upcoming birth.

September 16:  Being a Chimpanzee Mom

The length of a chimpanzee pregnancy is just slightly shorter than that of a human pregnancy at 8 months. Chimpanzee moms are very hands-on for the first several years of the infant’s life and typically have intervals of 4 to 6 years between births because of this. Even when a chimpanzee mother has another baby, the older siblings will typically still stay close to mom, giving the juvenile female offspring the opportunity to learn important skills about caring for infants that will aid them with their own offspring in the future. 

Chimpanzee babies will typically nurse from their mother for up to 5 years, even after regularly eating solid foods. Chimpanzees are born with very strong grasping abilities, as they need to cling to their mother’s belly as she climbs and moves around. As they get older they will transition to riding on their mom’s back. Eventually they will start to venture off of mom to explore and play, but always staying in close range and still climbing on her back for a ride when moving from place to place.

Being a chimpanzee mom is a very important and difficult job. They may have help from other members of the troop but they are the main caretaker and are responsible for keeping their offspring safe. Mother chimpanzees are also responsible for teaching their offspring what food to eat, how to act in the social hierarchy, how to use tools, how to build nests, and a lot of other vital information that will help the young chimpanzee survive and thrive. We are looking forward to seeing what an amazing mom Utamu will be!


Utamu and Rosebud

Utamu and Rosebud

Beauty and Utamu

September 23: Lifetime of Care

At the Saint Louis Zoo we are dedicated to caring for animals, and that includes providing high quality care throughout their lifetime. For chimpanzees and other apes, this can be quite a long time, and individual animals have different requirements throughout their lives. With a  multi-generational group and preparing for the birth of an infant chimpanzee, the primate care team has to make sure the habitat and care of our chimpanzee group considers each  animal’s unique needs. 

Since our youngest chimpanzee right now is 18, it’s been quite a while since we have had an infant chimpanzee in the group.  With lots of upgrades and changes since then, the primate care team is taking a close look at the habitat to make sure it meets the needs of an infant and growing chimpanzee.  Adult chimps are very agile, great climbers, very strong and intelligent. However, an infant has different needs as it grows and learns so we need to make sure the habitat is not only safe but also that it provides learning and exploration opportunities that are suitable for juvenile chimpanzee. 

We are not just modifying things for the upcoming baby, though. We also have to take into consideration the needs of the older chimpanzees in the group, two of which are close to 50 years old! These older ladies aren’t as spry as they used to be, so we recently upgraded their indoor dayroom habitat to allow for easier climbing, and added resting areas at the different levels. This was an awesome project funded by a generous anonymous donor! While older chimps are still much better climbers than most of us humans could ever be, as they age they may not be able to move around quite as smoothly. We constantly look for ways to ensure the best care for every individual of our chimp troop and their different stages of life!



September 30: Chimpanzee Groups

Chimpanzees are extremely social animals. They live in groups with multiple males and multiple females, and these communities can reach over 100 individuals! During the day, different sub-groups will break off to search for food and socialize, and then come back at night to join the rest of the community. This is called fission-fusion.  Our chimps at the Saint Louis Zoo are no different!  

Our chimpanzee group is made up of three males and six females. Throughout the day, the chimpanzees will spend time with different chimps and hang out in different areas in their indoor or outdoor habitat.  Friendship is extremely important to a chimp, so our chimps will often spend time grooming one another, eating together and playing!  Utamu, our mother-to-be, can frequently be seen resting and grooming with her mom, Rosebud.  She also loves to play with the other younger females of the group, Tammy and Bakhari.  One of her favorite members of the group to play with is our newest male Kijana. We often see them wrestling and laughing together.  Socializing, grooming and playing are very important in chimpanzee relationships and these activities help reinforce and build the bonds they have with one another. 
Utamu will be very protective of her new baby, but chimps close to Utamu will no doubt be spending a lot of time with Utamu and her new addition. Rosebud, the grandmother, and Beauty, another older member of the group, will no doubt dote on Utamu and the little one.  Once the infant is old enough, many individuals, such as Kijana, will be excited to play with Utamu and her new baby. We can’t wait to see the new relationships that will form with a new addition to our chimpanzee group!

October 7: Getting to Know Grandma Rosebud

Rosebud is the matriarch of the chimpanzee group here at the Saint Louis Zoo. She came to the Zoo from Busch Gardens Tampa Bay in 2007. Rosebud, or Rosie, as the keepers call her, was immediately loved by the other chimpanzees and really enjoys being outside. She is approximately 49 years old and the mother of our soon-to-be new mom, Utamu. Rosie has a very high social ranking in the chimpanzee group even at her advanced age. She has many friends within the group but her strong positive relationships with all three males is particularly helpful in maintaining her high social status.
Rosie is very playful and will have fun with nearly all of the other chimpanzees. Her favorite food is banana, which she gets nearly every morning, yet she still gets excited every time. Rosie can often be seen with her daughter grooming, or laying with her best friend Beauty near the viewing shelters in the chimpanzee outdoor habitat. She sleeps in the same place every night and builds the most comfortable nest you could ever see. You can easily pick Rosie out of the group by her distinct messy hair and with her typically being in the middle of any large grooming session.
Chimpanzee grandmothers play an integral role in how their offspring develop as mothers. Rosie, being such a good mother to Utamu and hopefully passing on those maternal skills, gives Utamu a helpful start in being a good mother to her new baby. In addition, Utamu will have the support of grandma Rosie to help take care of the new little one.
Continue to follow Utamu: Path to Motherhood at to learn more about Utamu’s pregnancy and the work being done by Saint Louis Zoo staff in preparation for the upcoming birth.

October 14: It Takes a Village

One of the things that not everyone realizes is how many teams and staff at the Saint Louis Zoo are involved and work together with the Primate Care Team to provide care to the apes and to prepare for a chimpanzee birth. We’d like to highlight three of these amazing teams!

The Saint Louis Zoo has a remarkable Nutrition department led by Debra Schmidt, Ph.D., William R. Orthwein, Jr. Family Animal Nutritionist. This team works every day to make sure all the animals in the Zoo have healthy diets tailored to their individual needs, both by working with the animal care staff to develop diets and by prepping and delivering these food items daily to all of the animal areas. This includes adapting their diets at different stages in their lives, such as Utamu’s pregnancy. One of the additions made to Utamu’s diet related to her pregnancy includes a daily pre-natal vitamin.  

The chimpanzee group gets fresh produce and greens delivered daily along with nutritionally complete biscuits and a variety of forage and browse items.

Another incredible group that contributes to the chimpanzees’ care at the Zoo is our Horticulture team. Many people notice the beautiful flowers and greenery around the zoo but don’t realize the work this team also contributes to the safety and care of the animals. The horticulturists work with the animal care teams to make sure that the plants within the animals’ habitats are safe for the species that live there. They regularly work in the habitats to make sure that nothing is growing within them that shouldn’t be and to keep the plants that should be in the habitat healthy. This can be a challenging task especially with animals as inquisitive and active as primates that love to use these trees and plants to climb, swing, snack, make tools and play!

Last but definitely not least is the Facilities Management team! This large crew is divided into various specialties and not only works to keep everything functioning, but this creative department also works with the animal care staff to develop innovative ideas to improve animal care. We mentioned in a recent post the addition of new perching in the chimpanzees’ indoor habitat to make it more accessible for the chimpanzees as they get older. This collaborative effort was a multi-step process, starting with the maintenance and care teams meeting to discuss the needs of the chimpanzees and how they use their existing habitat. Then came a test phase where a few of the ideas were installed and the chimpanzees given access for several days to determine which type of perching the chimpanzees preferred and utilized. Facilities Management helps support the animals behind-the-scenes as well, including specialized modifications to support Utamu’s pregnancy.  One of the many items created and installed by the welding team in preparation for a chimpanzee pregnancy and birth was a special training port and shelf for ultrasounds to aid in monitoring the pregnancy. These features have allowed the veterinary and primate teams to monitor Utamu’s pregnancy – stay tuned, more about this in a future installment! 

Photo 1: Drew in Animal Nutrition preparing produce for our apes.
Photo 2: Horticulture taking care of the habitat.
Photo 3: Steve in Horticulture taking care of the habitat.
Photo 4: Indoor habitat perching.
Photo 5: John and Colton in Facilities Management working on indoor habitat perching.
Photo 6: Drew in Facilities Management working on the ultrasound port.
Photo 7: Derek and Jeff in Facilities Management working on the ultrasound shelf.
Photo 8: New door for ultrasound port. 

October 21: Utamu's Ultrasound

Primate care staff train all the great apes many different veterinary and management behaviors in order to provide them with the utmost care possible. When training a chimpanzee we use positive reinforcement, which means we give them a tasty treat as a reward for participating. Each ape has their own personal favorite treats, so we like to find out what motivates each one to increase the likelihood they will choose to participate in the training sessions.

 When we found out Utamu was pregnant, we began training the ultrasound behavior right away. Utamu is highly food motivated and one of her favorite treats are grapes. We began with the use of a fake ultrasound “probe.” This was a plastic case shaped similarly to a real probe, but didn’t have the added expense a real probe may have just in case in the early stages of her training Utamu happened to be interested in trying to steal the probe to investigate it. Utamu would present her belly to the front of the steel mesh barrier and I would press the “probe” onto her lower abdomen.  Several other steps had to follow before performing a real ultrasound, such as adding ultrasound gel, increasing the time she allowed the “probe” on her lower abdomen and allowing the “probe” to move throughout her lower abdomen. 

 Once those steps were complete, we were ready to bring in a member of the veterinary team to perform a real ultrasound. However, bringing in a new person is part of the training process and she had to be desensitized, or familiarized, to their presence. Luckily, this step did not take long as she is a very relaxed chimpanzee and any additional staff present during her sessions did not seem to bother her. 

Now we were ready to move forward with performing an actual ultrasound. On the day of the first ultrasound, she participated like a champ; presenting her belly, holding for several minutes at a time and allowing us to get the first images of her baby! During her sessions, one keeper is navigating the probe, another keeper is continuously giving her rewards while watching her behavior and comfort level and the veterinarian is reading and recording the ultrasound images. 

We now perform regular ultrasounds to monitor the health of both Utamu and her baby and will always work to make it a positive experience for her while trying to monitor the health and well-being of the baby. 

October 28: Getting Excited For the Baby

As Utamu's pregnancy approaches full term, we asked the Jungle of the Ape keepers about the pregnancy and what it means for the chimpanzee group.

Continue to follow Utamu: Path to Motherhood at to learn more about Utamu’s pregnancy and the work being done by Saint Louis Zoo staff in preparation for the upcoming birth.