Stop castrating gorillas!

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European zoos are castrating healthy male gorillas as a management tool. Castration is both unnecessary and cruel, as there are several alternatives - please read on for more information. We believe that the castration of gorillas is wrong, and ask you to take action and sign this petition!

+++ News: Please read Neil Bemment's reply (in the News section further below on this page) that has some promising statements. However, they are not very precise and therefore raise more questions that I am addressing in my own reply. +++



In the wild gorillas live in family groups with one dominant silverback (adult male). When a young male matures he often leaves his natal group and lives alone or with other males until he gets his own group with females who leave their families. Adult males can live together in breeding and non-breeding groups with changing hierarchies over time, but not every silverback successfully breeds.

The Problem:

Zoos try to mimic the wild but cannot. Poor breeding policies have created too many gorillas related to too many others. Female gorillas are easier to manage than silverbacks, however, so there is a problem with “surplus males”. Castration not only “fixes” the problem of unwanted breeding but also changes the physical and psychological make up of the gorilla, making them easier to manage than a healthy silverback. It is comparable to lobotomies on problem humans of the past, used to change behavior. Herein lies the issue. The EEP opts for the cheaper/easier solution for the zoos, not the gorillas.

For instance, one zoo let breeding go unchecked and had six baby boys in five years. Recently two of those babies were maimed for life when they were castrated, with a third baby possibly awaiting the same fate.  

The Paradox:

Gorillas are an endangered species. Millions are spent to save them in the wild while we cruelly maim them in our zoos, allegedly for the sake of conserving their species. Brought into captivity and bred by us they deserve the best life possible. They are not a "sack of genetic material", as apparently considered by some officials, but unique individuals to whom we owe our respect.

The Science:

As of today, the EEP bases its “science” on the appropriateness of castration on just one gorilla. Kukuma (photo) was castrated as a youngster in the early 1990s, in an experiment to see if a castrated male “not needed for breeding” could live in a family group. He died at the early age of 21.

There are no scientific studies done on castrated gorillas, but there is a wealth of data on the negative effects castration has on humans and other primates including mood changes, depression, gradual bone-density loss resulting in osteoporosis, weight gain as well as severe heart problems. Someone who has met three adult castrated gorillas described them as “like powerful athletes ravished by disease, looking more like old lady gorillas without the sagittal crest or muscular chests and limbs like the magnificent silverbacks they were meant to be.”

Different Attitudes:

Two scientific zoo committees are in charge of all captive gorillas:

— SSP: North America, with approximately 344 gorillas in 54 zoos
— EEP: Europe and the rest of the world, with approx. 429 gorillas in 62 zoos

Castration is only being done by the EEP. The SSP does not use castrations despite having the same challenges before them. It has had a strict breeding policy in place for decades, wanting to maintain and stabilize their population, whereas the EEP wants to increase their numbers so breeding continues. Gorilla babies are important to the group, but not every gorilla needs to have countless babies as some have done in the EEP. For instance, Zurich’s silverback N’Gola has had 34 offspring, Bongo at Apenheul 24, and the female Lobo at Apenheul 11 so far.

Both the SSP and EEP have added several zoos with all-male groups which is a step in the right direction, but it’s more challenging. Some zoo directors prefer having baby gorillas to get more visitors (and more money) and they erroneously believe all-male groups aren’t good for the gorillas or the visitors. One zoo director said he would rather have a castrated gorilla living in his natal group than living in an all-male group, clearly not understanding/recognizing the wealth of social interactions all-male groups have, and how successful they can be given the confines of captivity itself. Many in favor of castration say euthanasia is the only alternative, which is simply not true.

Viable Alternatives to Castration:

As the SSP has shown, castrations are not necessary and can be avoided by

  • careful and strict breeding restrictions / recommendations
  • establishing all-male groups in more zoos
  • sending young males to be with lone gorillas in other zoos
  • returning gorillas to protected areas in Africa, like the Aspinall Foundation has successfully done
  • more “commerce” between the SSP and EEP zoos
  • fission/fusion groups, where breeding females spend time with different silverbacks, a relatively new trend which shows promise


Help us Help Gorillas

We are not anti-zoo, but history shows us that zoos don’t always do what’s best for the animals until time and public pressure convince them to change. We believe that the castration of gorillas is wrong, and ask you to take action and sign this petition! With your help, we want to tell EEP and EAZA (the umbrella organisation) to stop this cruel practice and to focus on the available alternatives.

We ask that no more gorillas be castrated at least until the 10 already maimed in Europe can be scientifically and properly studied. There is a lot of information on all-male groups but little to none on the effects of castration on gorillas. If we can’t get zoos to stop castrations altogether, at least they should have respectable science supporting their decisions!


Initiated by:

Esmay van Strien, Amsterdam, The Netherlands
Jörg Feiertag, Graz, Austria
Jane Rasmussen-Dewar, Morganton, United States


For more information, or if you have questions, please contact Jane.

And here is Dawn Forsythe's statement on this issue, shedding more light on the different attitudes of the EEP and SSP.

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