25 April 2018
The introduction during the past month proceeded without incident. The young gorilla spends a lot of time in her own enclosure, which is located in the corner of the large indoor enclosure. The entrance to this enclosure is big enough only for her and Shae. The youngest male often visits her here, and they play together and climb around in this space. She has a lot of contact with the other young males, too. They reach through the fence to grab her things or poke her playfully.
All of the members of the troop look out for Yanga, put each other in check if anyone is too rough and do not display any aggressive behaviour. However, closer ties than this have not been established between Yanga and any of the adult females, and consequently she has not found an adoption mother in the troop. As a result, the introduction process is taking longer than hoped for. Without an adoption mother, the young gorilla must fend for herself more. Under normal circumstances, young gorillas return to their mothers when they are tired of playing. Yanga cannot do this, and therefore she often retreats to her own enclosure. From here, she can still have contact with all of the gorillas, but only when she takes the initiative.
6 March 2018
Important step during the introduction: meeting the silverback
In the past month, the young gorilla practised being around the silverback for the first time. This was an important moment during the introduction. The three adult females and Shae, the members of the troop who had already visited Yanga in the enclosure on multiple occasions, were also present together with the silverback. The young gorilla sat in the separate area that is adjacent to the indoor enclosure. She could go to the group on her own. On the sixth practise day, she came out of her enclosure by her own choice. The silverback observed this from further away. After watching her for a little while, he began walking towards her. At first, he moved slowly, after which he picked up the pace. On the way, he grabbed a ball and tossed it through the enclosure. Yanga ran back into her enclosure. Nearing this enclosure, the silverback stopped and pounded his chest.
Although the exercise proceeded without aggression, the young gorilla did not receive the desired protection from the female gorillas during the meeting with the silverback. As a result, the decision was taken to first work on strengthening the ties between Yanga and the other members of the troop before practising again with the silverback. She now spends each day in the outdoor enclosure with the other young gorilla, his mother and the female gorilla Binti. The decision was also taken to allow the young males to join this group one by one. The first to be selected was Shae's older brother. This introduction proceeded without incident and another young male has been added to the group in the meantime: Binti's son.
Gorillas live in family troops. These troops have a clear hierarchy: there is one dominant male and a number of females with their young. The troop members behave submissively around the dominant male. If a troop member fails to respect the prevailing hierarchy, the silverback will intervene. He may chase the gorilla in question, give them a slap or a push, or pound on his chest. The submissive gorilla will respond by making itself smaller to demonstrate submissiveness. The relationships must also be re-established when meeting a new member of the troop, such as Yanga in this case, which is accompanied by dominant behaviour on the part of the silverback.
One of the reasons for introducing Yanga to the ARTIS gorilla troop is because the silverback is calm and tolerant. Nevertheless, he will most likely demonstrate his dominance in order to keep the troop together. It is impossible to predict how he will behave during an encounter with Yanga.
Gorillas at play
Young gorillas spend a lot of time playing together. This can get quite rough at times. Gorillas are strong animals and are very muscular from a young age and able to withstand a blow. From the very day they are born, they have enough strength to clamp tightly to their mother. Yanga is not even one and a half years old, but weighing in at 12 kilos, she can already pull herself up in the ropes. You can see how the gorillas in the troop tussle with each other a lot, and that it can seem awfully rough.
The other young gorilla is subjected to rough play, too. The older males swat him when he walks past, or try to push him off balance. They pound on his back, pull on one of his arms or legs and try to steal his food. Shae makes a screaming sound to indicate when it is time to intervene. His mother, the silverback or one of the other females will come to his assistance in response. This protection maintains the equilibrium of the relationships, which is why it is important that Yanga also receive protection within the troop.
The two older males that were added to the troop also play with Yanga a lot. They tussle with her or try to steal her blanket. Yanga then refuses to let go of the blanket, which the males interpret as a game. They also thump on her, just like they do with Shae. Yanga sometimes responds by making herself smaller, and lies down on the ground. This is her way of showing that she knows that she is the smallest of the troop. Young gorillas often make themselves small when an older troop member is nearby. This is how they demonstrate submissiveness.
The adult gorillas keep an eye on the youngsters. If things get too rough, they will intervene. Both Sindy and Binti appear to be protecting Yanga increasingly better, to a slight degree. Sindy disciplines her own offspring if they are too rough with Yanga, and Binti sometimes sits between the youngsters at play in order to get them to cease and desist.
The young gorilla can frequently be seen with the other gorillas in the outdoor enclosure. It is important for her to be able to focus on her fellow troop members and learn natural behaviour in the process. We kindly ask you not to interfere with this process and avoid trying to make contact with the young gorilla.
1 February 2018
Another step has been taken in introducing the baby gorilla into the gorilla troop. Over the past weeks, she has gradually grown accustomed to almost all troop members, and they have gotten used to her. The next step is introducing her to the silverback. This will involve practice sessions of a few hours every day over the course of the next few weeks. The baby gorilla will be in a separate part of the indoor enclosure, allowing her to seek out contact on her own initiative and also be able to retreat. She does so by cautiously sticking her head out from time to time.
After the partition separating Binti and Yanga was opened for the first time, a calm and measured approach has been taken. Although contact between Binti and Yanga is friendly and they tolerate each other's presence, there is little real interaction and Binti has yet to assume responsibility for looking after Yanga. Consequently, the partition between the baby gorilla's overnight enclosure and the overnight enclosure of one of the other female gorillas and her offspring, Sindy and Shae, was opened halfway. The young gorillas could fit through it, but not the mother gorilla. Interaction could be observed immediately. Shae stuck his head through the partition repeatedly the first time it was open in order to look at Yanga. Soon, he was not just looking, actually going all the way into Yanga's enclosure several times for a quick visit. Yanga was relaxed in response to the young male's arrival. When he tried to take a couple of grapes from her enclosure, she grabbed his hands to see what was in them.
The first day that the partition between Yanga and Shae and Sindy opened completely for the first time was suspenseful. Sindy made enthusiastic sounds. The two young gorillas quickly started playing together, and Yanga and Sindy touched each other several times. From this moment onward, the three gorillas have been spending a couple of hours together at least once a day. The play became increasingly rough, which is a good sign. This is how young gorillas interact. Yanga is growing and gaining muscle, allowing her to really join in the play. She learns quickly, and it is clear to see that she is able to read the signals from the other gorillas correctly. She understands that, when other gorillas make a coughing noise, it means that she needs to leave something alone, and she makes coughing sounds herself when she does not want something. In the meantime, the three gorillas have also spent time together in the indoor enclosure in the Gorilla House.
20 November 2017
A tension-filled moment. Today, the partition between the baby gorilla and her intended adoption mother was opened halfway for the first time. Yanga could go over to Binti, but the opening was too small for the adult gorilla to go over to the youngster's side. This gave the baby gorilla the option of retreating at any time.
Although the baby gorilla hid herself behind a curtain at first, she soon showed herself. It was still too soon for an encounter with Binti. The baby gorilla stayed in her own enclosure, but the intended adoption mother did sit close by and showed interest. Towards the end, Yanga walked over to the partition, but Binti had just headed in the opposite direction. After 20 minutes, the keepers closed the partition and considered the day a success. The two gorillas acted calmly and relaxed, which bodes well for the next stages of the introduction.
Today, the gorillas were given banana leaves to play with and chew on. The young gorilla was interested in the leaves, too. She instinctively used them to make a nest, just like gorillas who grow up in a gorilla troop.
Young gorillas act like toddlers, putting everything in their mouth. They do so not only to play, but also to taste. This is how they get accustomed to different tastes, and gradually become able to drink less milk. Yanga tasted and ate a wide variety of things today. The menu included kiwi, raspberry, egg, banana, rice, apples and pepper.
It will still be a while before the baby gorilla will no longer drink any milk at all. Young western lowland gorillas drink milk until they are three or four years old.
A step further
The baby gorilla is increasingly readily visible to the rest of the troop. Today, the potential adoption mother was separated from the troop. From the moment that Yanga appeared in the escape area, Binti sat next to her. She showed a great deal of interest the next night, too. The following day, the youngest male gorilla was very interested. Yanga took the initiative to make contact with the nearly two-year old male, and put her finger in his mouth.
A month later
In the meantime, it has been over a month since Yanga's arrival at ARTIS. She is still separated from the troop, and contact is slowly being expanded in small steps. The intended adoption mother is showing interest in the baby gorilla and frequently seeks her out. The silverback and the young males likewise pay attention to her. The latter frequently come by to look and push twigs through the partition as a way to make contact.
Wilhelma Zoologisch-Botanischer Garten
Two ARTIS zookeepers are travelling to the Wilhelma Zoologisch-Botanischer Garten in Stuttgart this week. This zoo has taken in baby gorillas from all over Europe and has experience with introducing baby gorillas to adoption mothers.
While exploring the indoor enclosure on 15 September, the baby gorilla climbs in the ropes for the first time. This requires the young gorilla to use the muscles in her arms intensively. Because she is still training these muscles, the climbing is not always easy for her.
Unlike human babies, gorilla babies cling to their mother's back. Yanga needs to learn this, too. Here, she is practising with one of the zookeepers.
2 September 2017
The first step was to let the gorillas see each other through a window. The females and the youngsters in the troop quickly came over to get a look at her. After a while, the silverback put his face close to the glass, too. Much to the staff's delight, the troop's reaction showed no signs of aggression. As from today, the baby gorilla is staying in an enclosure that is separated from the troop, but still visible to them.
30 August 2017
30 August was the big day; the baby gorilla arrived at ARTIS. In order to ensure a calm transition, her keeper accompanied her and stayed at ARTIS for several days. The baby gorilla was not immediately placed with the gorilla troop.
One of the first steps taken was to conduct an examination of the dung. This was to determine whether the gorilla is healthy or is carrying a disease. The examination was carried out in part by the staff veterinarians at ARTIS:
'I sent some of her excrement to an external laboratory and also performed my own study. The faeces were examined for parasites and bacteria. I performed the tests for eggs of worms in the excrement myself using two different methods. The external laboratory carried out the bacteria culture'.
To prevent the baby gorilla from potentially transmitting diseases to the troop, she was not allowed to be around the troop until the results were in. The final test results arrived in the evening: Yanga was healthy. The introduction to the troop could begin.
Visit to Hannover
From 4 to 5 July, ARTIS zookeepers visited Hannover Erlebnis Zoo to prepare for the arrival of the gorilla baby. The four zookeepers got to meet the gorilla baby and their German colleagues who had been caring for the young gorilla up until now. After the meeting, the zookeepers were able to draw up a plan.
Visit to Bristol Zoo
In August, a group of zookeepers travelled to Bristol Zoo. A gorilla was born via C-section here in early 2016. The operation left the mother incapacitated for a long time; she was too weak to care for the baby and an adoption mother had to be found. After one was found, the gorilla baby was able to be returned to the troop after 10 months.
‘Although the situation at Bristol Zoo was very different, we were still able to learn a lot from them. We spoke a great length with the zookeepers. They told us what went well and what they might have done differently. The information was extremely useful'.
Choice is for ARTIS
ARTIS is home to a calm, close-knit band of gorillas. The troop's silverback has a reputation for letting the playful young gorillas run roughshod over him. Nevertheless, he corrects them when necessary, and also intervenes if disputes arise between the females in the troop. He keeps the troop together this way. As for Yanga's 'adoption mother', all hopes are on Binti, a 25-year old female. She has previously raised two youngsters successfully. She is known for being caring and protective, including towards others' offspring.
All of the western lowland gorillas living in European zoos have been identified in a breeding programme (EEP). Together with a committee of experts, the coordinator embarked on a Europe-wide search to find a suitable gorilla troop in a zoo that was willing to help. The introduction of an unfamiliar gorilla into a new troop is a very complex undertaking, and lacks a predictable outcome.
29 October 2016
A western lowland gorilla (Gorilla gorilla gorilla) has been born at Erlebnis Zoo Hannover. It is a female, named Yanga. Under normal circumstances, young gorillas spend the first years of their lives with their mother. Things turned out differently for the gorilla baby at Hannover Erlebnis Zoo, however. Shortly after birth, she was rejected. Her mother did not hold her to her body or give her any milk. Without food, Yanga would not survive, so the zoo decided to separate her from the troop and assume responsibility for her care.
The baby gorilla could not return to her family troop on account of the agitation in the troop. To give her a chance to grow up in a natural way, the decision was taken to find a new troop in which she would hopefully be accepted