Visitors at Apenheul see numerous primate species and other animals. We are keen to teach our visitors more about the animals in Apenheul and about their situation in the wild. That is how we work to fulfil our mission of promoting love and respect for animals and nature. But evoking awe for nature is not the only reason for Apenheul’s existence. We also aim to contribute to species conservation (both in zoos and in the wild). Keeping animals raises ethical issues. We want to be open and transparent about how we deal with these issues. This Code of Ethics starts with an introduction about keeping animals and then sets out how Apenheul deals with (the most common) ethical issues.


It is Apenheul’s mission to promote love and respect for animals and nature among all its visitors. Sadly, many of the primates you can admire in our park are threatened with extinction in the wild. This is true for many other animal species too. Zoos can have an important part to play in maintaining endangered species. The number of  animal species that are being saved from extinction is still increasing, partly thanks to the work of zoos.


Keeping (exotic) animals is a complex endeavour. Apenheul is a member of the Dutch Association of Zoos (Nederlandse Vereniging van Dierentuinen, NVD) and the European Association of Zoos and Aquaria (EAZA). These organisations have codes of ethics with which their members must comply. Apenheul is a leading zoo in terms of animal welfare, the quality of its animal enclosures, the way it cares for its animals and its contribution to species conservation. We go even further than the joint standards compiled by zoos.

Breeding programmes

Apenheul does not take animals from the wild. In order to maintain (genetically) healthy groups of primates, we collaborate intensively with other zoos. We participate in several internationally coordinated breeding programmes, also referred to as EEPs (EAZA Ex situ Programmes). Simply put, zoos exchange animals with each other in order to maintain genetically healthy populations. We also share knowledge and expertise with each other about animal husbandry. In Europe, EAZA is responsible for the proper functioning of these breeding programmes and also monitors them. Participation in breeding programmes is mandatory for all EAZA zoos. Due to the knowledge and expertise within the EAZA community, we highly prefer to exchange animals for breeding programmes with other EAZA zoos.

There is an EEP for almost all the species at Apenheul. Each programme has its own EEP-coordinator who determines which animals are moved where. A species committee advises the coordinator. The committee consists of representatives from various zoos that hold the species and therefore have specialist knowledge about it. Apenheul coordinates the international breeding programmes for the Western lowland gorilla, the woolly monkey, the emperor tamarin and the East Javan langur. We are also represented on several species committees and TAG’s  (Taxon Advisory Group).

Animal management

All coordinators of breeding programmes have or develop long-term strategies for maintaining genetic variety and healthy animal populations they manage. In recent years many primate breeding programmes have become increasingly successful. In fact, more animals are being born than EAZA zoos can accommodate, which leads to a surplus. As a result, properly managing surplus animals is becoming an increasingly prominent task within most breeding programmes. There is no ‘one size fits all’ strategy. So zoos use a variety of methods to limit the growth of certain animal species and to keep surplus numbers as low as possible.

Animal welfare

Preventing a surplus is also a priority at Apenheul. First and foremost this is something we aim for ourselves, but it is also something coordinators of breeding programmes are requesting. This means we constantly have to align these requests with our own needs and possibilities. The wellbeing of the animals is always the absolute main priority in this context. Although measuring animal welfare is very complex and challenging, we are developing an animal welfare score. We are doing this in partnership with the NVD, EAZA and universities.

Back to the wild?

Usually, reintroducing animals to the wild is not an option. Reintroductions, such as that of the golden lion tamarin in Brazil in which Apenheul played an important role, must comply with strict requirements set out by the IUCN (International Union for the Conservation of Nature) and government legislation. Moreover, it is a very lengthy process requiring intensive collaboration between numerous organisations and it costs a lot of time, money and resources. In addition, we must prevent inbreeding and to avoid introducing diseases into the wild, there has to be sufficient suitable habitat and it is essential that the initial threats  have been removed. For reintroductions, the most suitable animals in a breeding programme are selected and these are rarely the surplus animals.

The most common ethical issues

As previously mentioned, keeping animals raises ethical issues. Keeping animals with high animal welfare standards is a big responsibility. What follows is a description of how Apenheul deals with the most common ethical issues. There is a lot of ongoing debate about animal welfare and ethics. That is why we annually review which animals we keep at Apenheul and why. The Apenheul Management Team (MT) also annually reviews and approves our Code of Ethics. Together, Mrs Sterck and Mr Verstappen form the animal committee within the supervisory board and they participate in reassessing the Code of Ethics.

In addition, Apenheul has an Ethics Committee consisting of our biologist, curator, veterinarian, two zookeepers and two employees without an animal care related position. This committee is consulted when ethical questions arise. The curator discusses the situation with the veterinarian and puts forward a proposal. The Ethics Committee then checks whether all options have been adequately investigated and then formulates a proposal. The final decision is taken by the MT.

  1. Feeding by visitors

Visitors at Apenheul are not allowed to feed the animals. All the animals at Apenheul receive a diet that is professionally composed by our nutritionist. It is very important for their health that we do not deviate from that diet. The wrong food can cause animals to become seriously ill. Moreover, we aim to stimulate the animals’ natural behaviour by making them search for their food themselves. Sometimes, visitors participate in feeding the animals. For example, in the context of special arrangements like ‘caretaker for a day’ or visitors who are allowed to ‘help’ zookeepers to do the feeding. In all such cases, the feeding is always supervised by an experienced zookeeper.

  1. Presentations involving animals

Apenheul aims to educate visitors in a fun way about the animals in the park and their conspecifics in the wild. One way we do this is through (feeding) presentations in the park. We then follow EAZA guidelines for using animals in public demonstrations. We never force animals to participate in a (feeding)presentation. We also do not use any type of coercion and we do not encourage unnatural behaviour. The food the animals receive during a feeding session is an addition to their diet and is not part of their daily nutritional needs.

  1. Hand raising

As far as possible, Apenheul allows all its animals to live a natural life. That means that we let mothers feed their young themselves and that zookeepers do not hand-raise newborn. We only make an exception in the case of species that are so rare that each surviving young will have a large impact on the breeding programme. For example, in the case of species such as the blue-eyed black lemur and the crowned sifaka. We may also distinguish between male and female young (i.e., we feed one but not the other). This depends on the demographic structure of the population.

  1. Long-term treatment of sick animals

It goes without saying that we treat sick animals at Apenheul. Sometimes this requires a lengthy treatment that (seriously) impacts the animal’s quality of life. We discuss such cases with the Ethics Committee and the veterinarian to determine whether the treatment might cause the animal too much suffering and whether we should consider euthanising it instead. For example, this might be a situation in which the animal has to be (very) regularly ‘caught’ or when an social animal has to be isolated from the rest of the group for extended periods of time.

  1. Euthenasing (terminally) sick animals

In Apenheul’s opinion, if a sick or injured animal cannot or can no longer be treated, the best option is to euthanise it. This also applies to animals carrying a disease which is a danger to humans or other animals. In such cases we follow instructions from the government and/or veterinarian.

  1. Shortage of suitable accommodation

As in all zoos, there are some animals living at Apenheul who will have to leave. This might be because we need to prevent inbreeding or because a particular animal is causing too much stress in the group. It can sometimes take a long time to find a suitable destination for an animal. The EEP coordinator will look for an institution for all EEP animals. In the case of non-EEP animals, Apenheul itself will undertake the task. As long as we have a suitable enclosure in Apenheul, this is not a problem. However, it can happen that all suitable enclosures are occupied or that it takes too long to find a suitable institution. In this type of situation the animal’s welfare may be seriously compromised. We address this type of situation further on in this document.

  1. Moming animals to non-EAZA zoos

Apenheul does not move animals to zoos where the animal’s wellbeing cannot be guaranteed. That is why a transfer to an EAZA zoo always is always our first choice. The reason for this is that zoos must comply with a series of important requirements regarding animal welfare before they can be become members of EAZA. Transfer to a non-EAZA zoo is not our preference, but we do not rule it out completely. If this situation arises with respect to EEP species, we must first get approval from the EEP coordinator. The make sure that the institution meetsour high standards,we carry out these inspections ourselves at zoos we have not visited before. In some cases we will rely on inspections carried out previously by another EAZA zoo. It is important that we make arrangements with the zoo about supervision of the animals. Apenheul always makes it a priority to remain as actively involved as possible with the animals at their new home. In addition, a zookeeper almost always accompanies the animal for the first few days after it is transfered, to share knowledge and experience about the species and the individual animal with its new keepers.

  1. Temporary contraception

When necessary, Apenheul administers (contraceptives)to regulate reproduction. We always use whatever contraceptives are most suitable for the species and which best match the situation. Apenheul may have various reasons for administering contraception. Examples might be to prevent inbreeding, medical reasons, situations in which the group would otherwise become too big or if there is a shortage of transfer options.

  1. Sterilisation and castration

Apenheul applies both sterilisation and castration. Several female animals have been sterilised. Various male animals have been castrated too so that we can keep them in their natal groups. This is often done on recommendation by the EEP coordinator. Generally speaking, castrated males do not cause problems in social groups. In the case of some species it is not yet known what percentage of castrated males a group can tolerate. We are researching this for a number of species. We are doing this research in collaboration with several national and international universities and other EAZA zoos. In particular for great apes we use reversible contraception such as implants.

  1. ‘Single-sex groups

Some groups living at Apenheul consist of only male or female individuals. These groups are also referred to as ‘single-sex’ or ‘bachelor’ groups. We also transfer animals to other zoos that have similar groups. Apenheul’s experience with this type of group has been mainly positive.

  1. Stress reduction

Apenheul sometimes treats animals with medication to reduce stress and/or to relieve anxiety (psychopharmaceutical drugs). We do this, for example, to prevent tense situations from escalating or to calm animals that are displaying anxious behaviour for some reason. We never use these medications for long, always for a short time. For instance, when a new animal is introduced into a group.

  1. Possibilities when animal welfare might become  compromised

It can happen that the welfare of one or more animals in a group becomes threatened, for example when the group composition changes. Groups can become too large or too complex. Sometimes young males will undermine the authority of the leader. Such situations can lead to fighting, group instability or to the ostracising of sub-adult animals. This is often natural behaviour. If the wellbeing of an animal or a group of animals comes under threat, we always firstly look for an internal solution. If this is not available (e.g., due to shortage of suitable enclosures) we might revert to a transfer to an EAZA zoo. We prefer not to transfer animals to non-EAZA zoos, but we do not rule this out entirely. If there is no option at all available for the long-term and we are not able to improve the animal’s welfare, we may ultimatelydecide to euthanise it. We emphasise that this is always a last resort and such a decision is only taken after extensive deliberations with the veterinarian and the Ethics Committee. We constantly strive to prevent, reduce and fine-tune such situations, to which end we sometimes consult with independent experts.

  1. Allowing animals to reproduce for the benifit of group wellbeing

For most animal species, a major component of wellbeing is the dynamic of a natural group in which animals are born, grow up and then leave. Their behaviour and needs are completely adapted to life in a social group. Complete or partial contraception of primates influences the dynamic in their groups. This can (sometimes) negatively affect their welfare in the long run. If young animals are able to move to other, high-quality zoos then this is not a problem. However, it can happen that for a lengthy period there is nowhere for the young animals to go. In such circumstances we face an ethical dilemma and we have to weigh up the welfare of the group against the individual animal’s wellbeing. The available options are discussed in detail with the EEP coordinator and agreed within EAZA. In some situations it is possible to allow (some) females to reproduce even when we know on beforehand there is likelihood chance that we will have to euthanise these young. In other situations, however, it might be better for the welfare of the group to remove older animals to maintain the group’s stability and demographic structure.

In conclusion

Keeping animals involves a huge responsibility and we are well aware of this at Apenheul. We constantly strive to improve husbandry, nutrition and general care for the animals. Good animal welfare is essential and is our top priority. We understand that there is a lot of debate about animal welfare and ethics and that we are not able to manage this alone. That is why we collaborate with various universities and other knowledge institutes to expand and share our knowledge about primates.