Australasian Western Lowland Gorilla Population

[Zoofan15]

Buluman was apparently extremely patient. I believe there was a story about him and a butterfly?

No, it was that damn caterpillar. It appeared one day in his cage and and terrified him - presumably due to a generalised and instinctive fear great apes have to anything resembling a snake. Buluman decided to solve the problem by heaping hay on the caterpillar and calmed down. To his horror, the caterpillar emerged from the top of the pile and he retreated to the furthest corner of the cage.

 

[Zoofan15]

Yuska has died at Melbourne Zoo

Some sad news from Zoos Victoria’s social media:

Zoos Victoria is heartbroken to share that Melbourne Zoo’s much-loved matriarch Western Lowland Gorilla, Yuska, has died. Yuska was one of the oldest known gorillas in the world and inspired so much joy and wonder among generations of animal lovers.

At 51 years of age, Yuska experienced significant age-related health problems over many years, including dental issues, arthritis, a partial loss of eyesight and a series of recent minor strokes or seizures. These persistent health problems led Melbourne Zoo’s keepers and vets to determine that the kindest, most humane welfare decision for Yuska was euthanasia.

Yuska’s legacy to the conservation of the Critically Endangered Western Lowland Gorilla species is extraordinary - from becoming world-famous in 1984 when she gave birth to Mzuri through artificial insemination, to later becoming a grandmother, great-grandmother and great-great grandmother. Her passing is a huge loss for Zoos Victoria’s community and Melbourne Zoo primate keepers both past and present who have cared for Yuska over many years.

——————————————

Yuska’s death reduces the zoo’s troop to 1.2 gorillas:

1.0 Otana (28/01/2001) Kouillou x Tamba; Imported 2013
0.1 Kimya (12/01/2005) Kibabu x Kriba
0.1 Kanzi (14/03/2015) Otana x Kimya

 

[Abbey]

Continuing on the discussion from the Melbourne Zoo News 2022 thread, the 1992 Global Primate Action Plan includes a note about artificial insemination in gorillas:

"Helen Shaw has been accumulating samples from G'Anne at Jersey and semen is being collected from various males . . . Several other females are candidates for AI including Sidonie at Howletts, Naomi at Edinburgh, and Julia at Jersey."

 

[Zoofan15]

Continuing on the discussion from the Melbourne Zoo News 2022 thread, the 1992 Global Primate Action Plan includes a note about artificial insemination in gorillas:

"Helen Shaw has been accumulating samples from G'Anne at Jersey and semen is being collected from various males . . . Several other females are candidates for AI including Sidonie at Howletts, Naomi at Edinburgh, and Julia at Jersey."

That's interesting that both G-Anne and Julia had been identified as candidates for AI. The meetings began in 1991, so at the end of Jambo's life (he died in 1992), who was their silverback at the time. Though he'd accepted them, they obviously had little confidence a successful mating would take place.

Jersey's next silveback was young and inexperienced and had little tolerance for these socially abnormal females. Intestingly they found both acceptance and breeding success with Jambo's son at Melbourne.

On a contemporary note, AI would be most applicable to Johari at Melbourne; but could also have applications towards improving the genetic diversity across troops in the region.

 

[Zorro]

Yuska has died at Melbourne Zoo

Some sad news from Zoos Victoria’s social media:

Zoos Victoria is heartbroken to share that Melbourne Zoo’s much-loved matriarch Western Lowland Gorilla, Yuska, has died. Yuska was one of the oldest known gorillas in the world and inspired so much joy and wonder among generations of animal lovers.

At 51 years of age, Yuska experienced significant age-related health problems over many years, including dental issues, arthritis, a partial loss of eyesight and a series of recent minor strokes or seizures. These persistent health problems led Melbourne Zoo’s keepers and vets to determine that the kindest, most humane welfare decision for Yuska was euthanasia.

Yuska’s legacy to the conservation of the Critically Endangered Western Lowland Gorilla species is extraordinary - from becoming world-famous in 1984 when she gave birth to Mzuri through artificial insemination, to later becoming a grandmother, great-grandmother and great-great grandmother. Her passing is a huge loss for Zoos Victoria’s community and Melbourne Zoo primate keepers both past and present who have cared for Yuska over many years.

——————————————

Yuska’s death reduces the zoo’s troop to 1.2 gorillas:

1.0 Otana (28/01/2001) Kouillou x Tamba; Imported 2013
0.1 Kimya (12/01/2005) Kibabu x Kriba
0.1 Kanzi (14/03/2015) Otana x Kimya

Melbourne zoos troop is shrinking fast I never thought it would get this small

 

[Zoofan15]

Melbourne zoos troop is shrinking fast I never thought it would get this small

Psychologically, it's unlikely Kimya regards her daughter as another adult female, so she's essentially living in a 1.1 pair with Orana, which would be making her feel uneasy.

Melbourne are in desperate need of importanced given there's no suitable females available within the region. Long term, Fikiri (2019) will likely go to Melbourne (assuming Kibale remains as silverback of her troop), but that's still 4-5 years away, so Melbourne need to act now.

 

[Abbey]

Psychologically, it's unlikely Kimya regards her daughter as another adult female, so she's essentially living in a 1.1 pair with Orana, which would be making her feel uneasy.

Melbourne are in desperate need of importanced given there's no suitable females available within the region. Long term, Fikiri (2019) will likely go to Melbourne (assuming Kibale remains as silverback of her troop), but that's still 4-5 years away, so Melbourne need to act now.

Hopefully the passing of Yuska, while a sad event, will put Melbourne in a better position to import two adult females, both to provide fresh bloodlines, but also to expand the troop and support Kimya.

 

[Zoofan15]

Hopefully the passing of Yuska, while a sad event, will put Melbourne in a better position to import two adult females, both to provide fresh bloodlines, but also to expand the troop and support Kimya.

I’m hoping so too. Given Yuska’s age, the best course of action was to delay introducing new females until after her passing, but there’s now an opportunity to do this.

Two unrelated females would be ideal as this wouldn’t leave Kimya excluded once Kanzi transfers out. Potentially this could occur in a swap with Taronga for Fikiri around 2026, once the younger female is also at the age of dispersal. The alternative would be for Kanzi to remain in the troop long term as a non breeding female, in which case the import of two related females would be acceptable.

 

[Abbey]

I’m hoping so too. Given Yuska’s age, the best course of action was to delay introducing new females until after her passing, but there’s now an opportunity to do this.

Two unrelated females would be ideal as this wouldn’t leave Kimya excluded once Kanzi transfers out. Potentially this could occur in a swap with Taronga for Fikiri around 2026, once the younger female is also at the age of dispersal. The alternative would be for Kanzi to remain in the troop long term as a non breeding female, in which case the import of two related females would be acceptable.

That's a good point about a potential future swap between Taronga and Melbourne for Fikiri and Kanzi. I'd thought in the past that Kanzi might end up at Mogo, particularly if/when Kriba passes away, although hopefully she's at least got another decade or so left in her like Yuska. While she's from a well-represented line, given our low number of females, it would be great if she is able to be in a breeding troop in the future.

Taronga are in an interesting position. On the surface, as the largest troop within the region and the most recent to breed, they need to be in the best position; however, going forward, Mbeli is likely the only breeding female. Further offspring from Mbeli and Kibali aren't necessarily that valuable within the regional population, particularly males.

As far as I'm aware, Taronga is currently planning on building two gorilla exhibits within their new Congo Forest precinct, although this might not be complete until 2025 at the earliest.

 

[Zoofan15]

When I contacted them earlier this year, Taronga Zoo were still planning a Congo precinct centred around Western lowland gorilla - with both a breeding troop and a bachelor troop.

While I think a swap between Taronga and Melbourne is more likely, my preference would be for them to move Kibale and his three sons into a bachelor troop and bring in a new silverback to head up a troop of Frala, Johari, Mbeli and Fikiri (with the two youngest females breeding). Sadly this plan is unlikely given Johari is accepted by Kibale versus the risk of bringing in a new male.

Either one of these ideas could tie in with Kanzi going to Mogo. Taronga’s need isn’t so great as they have two non breeding females in addition to the breeding female; though like you say, they have a 1.1 pair that aren’t producing very valuable offspring. Their two sons will likely never breed (with Fabumi joining them). Fikiri’s saving grace is she’s a female - as well as being less represented on her maternal side than her half siblings.

 

[Jambo]

When I contacted them earlier this year, Taronga Zoo were still planning a Congo precinct centred around Western lowland gorilla - with both a breeding troop and a bachelor troop.

While I think a swap between Taronga and Melbourne is more likely, my preference would be for them to move Kibale and his three sons into a bachelor troop and bring in a new silverback to head up a troop of Frala, Johari, Mbeli and Fikiri (with the two youngest females breeding). Sadly this plan is unlikely given Johari is accepted by Kibale versus the risk of bringing in a new male.

Either one of these ideas could tie in with Kanzi going to Mogo. Taronga’s need isn’t so great as they have two non breeding females in addition to the breeding female; though like you say, they have a 1.1 pair that aren’t producing very valuable offspring. Their two sons will likely never breed (with Fabumi joining them). Fikiri’s saving grace is she’s a female - as well as being less represented on her maternal side than her half siblings.

I think the bachelor group will be centered around Mjukkee, Fabumi and Mwamba. Kibali will likely remain as Taronga's silverback at least for the time being.

The best option in my opinion is to do a three female move between all three facilities (Melbourne, Taronga and Mogo). That would be; sending Fikiri to Melbourne (alongside a female or two from overseas), sending Mbeli to Mogo, and sending Kanzi to Taronga. This'll allow a new pairing at Taronga; between Kibali and Kanzi, whilst still allowing Kibali to stay silverback.

Future offspring of Kibali and Mbeli won't necessarily be valuable, and retaining her at Taronga alongside Frala, Johari and possibly even Kanzi will take up a lot of space when she could be used for breeding elsewhere.

 

[Zoofan15]

I think the bachelor group will be centered around Mjukkee, Fabumi and Mwamba. Kibali will likely remain as Taronga's silverback at least for the time being.

The best option in my opinion is to do a three female move between all three facilities (Melbourne, Taronga and Mogo). That would be; sending Fikiri to Melbourne (alongside a female or two from overseas), sending Mbeli to Mogo, and sending Kanzi to Taronga. This'll allow a new pairing at Taronga; between Kibali and Kanzi, whilst still allowing Kibali to stay silverback.

Future offspring of Kibali and Mbeli won't necessarily be valuable, and retaining her at Taronga alongside Frala, Johari and possibly even Kanzi will take up a lot of space when she could be used for breeding elsewhere.

That sounds feasible, with the only addition I’d make being to import an additional female for Taronga, who would otherwise have only one viable female.

Potential Plan

This plan could potentially be implemented over the next four years, under the following timeframe:

2023: Melbourne import one young female

2024: Bachelor troop created at Taronga; Mbeli transfer to Mogo

2026: Fikiri transfer to Melbourne; Kanzi transfer to Taronga; Taronga import one young female

The Taronga transfers could be delayed a year or two to correlate with the new facilities being built. The move to the new exhibit would be the ideal time to introduce new gorillas to the troop.

Mbeli would remain on contraception until her transfer to Mogo in 2024; while Melbourne’s imported female would remain on contraception until 2026, so as not to disadvantage Fikiri.

 

[Swanson02]

That sounds feasible, with the only addition I’d make being to import an additional female for Taronga, who would otherwise have only one viable female.

Potential Plan

This plan could potentially be implemented over the next four years, under the following timeframe:

2023: Melbourne import one young female

2024: Bachelor troop created at Taronga; Mbeli transfer to Mogo

2026: Fikiri transfer to Melbourne; Kanzi transfer to Taronga; Taronga import one young female

The Taronga transfers could be delayed a year or two to correlate with the new facilities being built. The move to the new exhibit would be the ideal time to introduce new gorillas to the troop.

Mbeli would remain on contraception until her transfer to Mogo in 2024; while Melbourne’s imported female would remain on contraception until 2026, so as not to disadvantage Fikiri.

I think that plan is pretty sound
My only qualm is Melbourne's current plan with Otana? I understand he has matured a bit but I'd be wary of his bad history if I was any zoo sending young females to Melbourne. There is an excess of unrelated males in Europe. I understand it would be cruel to send him to Werribee or Mogo to live out the rest of his life in solitude. But is it really worth risking the life of another female for him to produce a son to accompany him in retirement?

I'll admit I'm rather uneducated on our gorilla situation but I thought Melbourne's plan was to wait until Yuska passed before shifting on Otana and introducing a couple of new females and eventually a new mature silverback.

 

[Zoofan15]

I think that plan is pretty sound
My only qualm is Melbourne's current plan with Otana? I understand he has matured a bit but I'd be wary of his bad history if I was any zoo sending young females to Melbourne. There is an excess of unrelated males in Europe. I understand it would be cruel to send him to Werribee or Mogo to live out the rest of his life in solitude. But is it really worth risking the life of another female for him to produce a son to accompany him in retirement?

I'll admit I'm rather uneducated on our gorilla situation but I thought Melbourne's plan was to wait until Yuska passed before shifting on Otana and introducing a couple of new females and eventaually a new mature silverback.

I too had wondered if the plan was to swap Otana out for a new male and indeed now is the perfect time to do it given they have no infants or juveniles in the troop and Kimya isn't pregnant.

However, the information I've received is that Otana will remain as head of the troop long term given there's no options of placing him in a bachelor troop.

His intolerance of Julia and G-Ann was typical of a young silverback maturing into the role and it's hoped that as a matured silver back, he'd react differently to immigrant females. In any case, I'd be confident that socially normal, mother raised females would be in no danger and be accepted as Kimya was. As a wise precaution, these are the only females Melbourne are likely to acquire.

 

[Pertinax]

His intolerance of Julia and G-Ann was typical of a young silverback maturing into the role and it's hoped that as a matured silver back, he'd react differently to immigrant females. In any case, I'd be confident that socially normal, mother raised females would be in no danger and be accepted as Kimya was. As a wise precaution, these are the only females Melbourne are likely to acquire.

I think Otana has been rather unfairly blacklisted because of the unfortunate events surrounding Julia's death. I'm pretty sure he is perfectly normal and the combination of his youth/inexperience and being placed with two desocialised females was largely to blame. Give him more properly socialised (mother-raised) females now and I'm sure there would be no problem. As I've mentioned before, this problem has arisen in European groups previously-young males that are initially aggressive but as they become older settle to become model fathers and group leaders. Buzandi, ex Melbourne, now at Hanover, is a case in point. Yaounde at Valle des Singes is another. America do not add young silverbacks under about 18 years as group males, so seem not to suffer from this problem.

 

[Zoofan15]

I think Otana has been rather unfairly blacklisted because of the unfortunate events surrounding Julia's death. I'm pretty sure he is perfectly normal and the combination of his youth/inexperience and being placed with two desocialised females was largely to blame. Give him more properly socialised (mother-raised) females now and I'm sure there would be no problem. As I've mentioned before, this problem has arisen in European groups previously-young males that are initially aggressive but as they become older settle to become model fathers and group leaders. Buzandi, ex Melbourne, now at Hanover, is a case in point. Yaounde at Valle des Singes is another. America do not add young silverbacks under about 18 years as group males, so seem not to suffer from this problem.

I’d agree with that. He wasn’t the first silverback to have a problem with Julia and G-Anne - with the other (Mzuri) also a young male like himself. He’s proved a capable silverback with Kimya and Yuska, with the latter being accepted into his troop despite her minor social deficiencies. It’s also worth noting that the incident with Julia partly stemmed from his protectiveness of Kimya, who had a newborn at the time.

The best course of action may be to import a mother raised female and if there’s any issues with her integration, transfer Fikiri to Mogo instead. Otherwise, she could potentially become Otana’s third female.

 

[Pertinax]

I wouldn't normally advocate the adding of too-young males e.g. under (say) 12 years old to groups but there's a couple of situations where that style of management can prove beneficial.

1. Where's there's an older non-breeding silverback who doesn't breed. Adding a young blackback male he will tolerate may allow breeding to commence without removing the old silverback. They have done this successfully at Rostock though I recently saw video that clearly showed the now 10 year old male aggressively challenging the old one.

2. Where the group silverback dies but a small infant/s are left in the group. Adding a new much younger male may be safely possible a lot sooner than a fresh silverback, to allow continuity.

 

[Zoofan15]

Where's there's an older non-breeding silverback who doesn't breed. Adding a young blackback male he will tolerate may allow breeding to commence without removing the old silverback. They have done this successfully at Rostock though I recently saw video that clearly showed the now 10 year old male aggressively challenging the old one.

Motaba at Melbourne is to date the only region’s only example of this. He arrived as a six year old in March 1990 and successfully bred with one of the females the following year in a troop led by a sterile silverback. It was successful due to the nature of Buluman, who was unusually docile for a male of his species.

I feel like part of the reason zoos have imported young silverbacks in recent years (Kibale, Otana and Kisane were all 11-13 years) is due to Australasia’s geographical isolation. If they’re going to the expense of importing, they want a gorilla that’s statistically likely to last at least 20 years.

What’s important for zoos to consider are gone are the days where silverbacks assume leadership of a troop as adolescents and breed continuously until their death two or three decades later. Due to the overcrowding of this species’ captive population, breeding is far more restrictive and it’s more common to see a silverback father a handful of infants and then retire.

 

[Abbey]

Motaba at Melbourne is to date the only region’s only example of this. He arrived as a six year old in March 1990 and successfully bred with one of the females the following year in a troop led by a sterile silverback. It was successful due to the nature of Buluman, who was unusually docile for a male of his species.

I feel like part of the reason zoos have imported young silverbacks in recent years (Kibale, Otana and Kisane were all 11-13 years) is due to Australasia’s geographical isolation. If they’re going to the expense of importing, they want a gorilla that’s statistically likely to last at least 20 years.

What’s important for zoos to consider are gone are the days where silverbacks assume leadership of a troop as adolescents and breed continuously until their death two or three decades later. Due to the overcrowding of this species’ captive population, breeding is far more restrictive and it’s more common to see a silverback father a handful of infants and then retire.

I agree with both your points. Furthermore, when Taronga imported Kibale, they were in a position to import before he actually needed to be introduced to a troop. Kibale's story is a case in point for your second point, although it would have likely been a different story were Johari a socially 'normal' female, as they likely would have otherwise produced offspring.

If anything, importing an older silverback means, as crude as it might sound, there will be fewer years of his life in which he'll either need to live in a non-breeding troop (a la Kibabu), or in a bachelor group with sons (like Motaba). Otana is in a unique situation due to only having one female (Kimya) with whom he's had the opportunity to breed. That said, were Julia and G-Anne post-reproductive by the time he arrived?

 

[Zoofan15]

I agree with both your points. Furthermore, when Taronga imported Kibale, they were in a position to import before he actually needed to be introduced to a troop. Kibale's story is a case in point for your second point, although it would have likely been a different story were Johari a socially 'normal' female, as they likely would have otherwise produced offspring.

If anything, importing an older silverback means, as crude as it might sound, there will be fewer years of his life in which he'll either need to live in a non-breeding troop (a la Kibabu), or in a bachelor group with sons (like Motaba). Otana is in a unique situation due to only having one female (Kimya) with whom he's had the opportunity to breed. That said, were Julia and G-Anne post-reproductive by the time he arrived?

Very true. Kibale lived in a 1.1 pair with Kimya from early 2012 to late 2013 - when Kimya was swapped for Mbeli and Johari from Melbourne Zoo and Frala rejoined the troop after being isolated with her sons prior to their export. On hindsight, Kibale coped remarkably well considering he accepted Johari; and that Frala was a fiery, older female. In any event, Frala proved respectful of Kibale from the start and assimilated nicely into the troop.

That’s what I was thinking re. importing an older silverback. Importing a male of 25 years would mean he could head up a breeding troop for his remaining years (10-15), which is the typical tenure of a breeding male for genetic diversification reasons.

G-Anne was 34 years old and Julia was 31 years old when Otana was imported in 2013, so still of reproductive age. Females of this species reproduce reliably up until their late 30’s (Frala holds the regional record at 38 years) - with a few isolated cases overseas producing offspring in their 40’s. Sometimes a female cycling can cause issues though as it subjects her to unwanted attention from the silverback (and frustration/aggression when they reject him). For this reason, Johari was put on contraception.