Top image: Scientists create embryos, hope to save near-extinct rhino

For every species in a zoo there is usually an introduction strategy. Some of the introductions are present in, for example, the EAZA guidelines for particular species described underneath. For a long time I’ve been wondering if this is really the best way to introduce animals. We need to remember that these are ‘guidelines’ and we need to not just be complacent with what the species coordinator has written down. We need to think “What if there is a better way?” I am a firm believer that we need to look at the way we do things constantly. Animals are behaving all the time and maybe we can use these behaviours to make introductions within zoos better.

I’ve been involved with many animal introductions, some have been very successful and some have had many failings, that could’ve been solved in the preplanning stages. For the welfare of the animal, I think we need to look further into the behaviour of the animals we are introducing. Why would we do it a certain way with one species and a different way with a different species? Of course they have to find their own place in the group, but we as care givers are able to help them achieve this and provide some positive feedback to the rest of the group. By following these guidelines do we apply best practise?

Examples of EAZA’s best practise guidelines of 2 species:

Burmese brow antlered deer (Rucervus eldii thamin)

Burmese brow antlered deer (Rucervus eldii thamin)

“Introducing a new female: Females can be introduced with few issues, again, because their hierarchies are established relatively quickly.

Introducing a new male: Introductions of males to females outside of the breeding period can be relatively straightforward. Introducing male conspecifics should only be completed outside of the breeding season.

Introductions for breeding purposes: Hosack et al. (1999) established that housing a group of female Burmese brow antlered deer with a stag improved ovarian function and oestrus synchronisation.”

You can see directly that there is not any behavioural management in place, where we can have control of the behaviour that is seen in the animals.

White rhinoceros (Ceratotherium simum)

“During the introduction of an animal, the following steps may be taken:

Provide auditory, olfactory, and visual contact between the newcomer and the herd. Provide tactile contact through bars with a few members of the group. The individual is first introduced to either the dominant animal or the entire group.

During the introduction a veterinarian, as well as experienced staff members should be present with a high pressure water hose or a car, to intervene (Goltenboth et al., 2001).

The part where we need to be ready to intervene is a funny one, because what if we focus on the opposite instead? We try to make sure we don’t have to intervene or that the chances are very small. – PG

Introducing a female in a female group

Prior to first contact, the female should be familiarised with the outdoor enclosure. Indoors, females should have eye contact through bars. One could choose to get the new rhino introduced to the “calmest” rhino from the group and continue from there. Before the final introduction they should no longer show aggression. Introduction while a female is in oestrus can be beneficial. Close observations should be continued after the introduction. (Goltenboth et al., 2001)

Introducing a male to a female group

Male rhinos are territorial, they mark their territory with faeces and urine, scraping hind legs and spreading dung. A male’s marking should not be removed prior to introduction of the female group. Females tend to form strong pair bonds, even if not related. In some cases this has interfered with breeding, when the female’s cage mates keep driving off the approaching male.

A second male kept in an adjacent enclosure may stimulate breeding through potential competition. (Goltenboth et al., 2001) The second male can be held in the surplus area and when necessary be introduced to the group of females for mating. A possible disadvantage of such a system can be that there is a risk that the second male is more busy with establishing his territory than with breeding. Another disadvantage is the fact that you don’t know which male is the dominant one before introducing them. This can also lead to social suppression. It is not a good idea to do a male-female introduction while a female is in oestrus, because of the continued interest of the male in the female. Integration is reported to take 5 weeks (Goltenboth et al., 2001), but a full, stable integration might take much longer. Male rhinos are often tolerated but not really accepted.

When you read this information you can directly say that conditioning animals to each other with active training is not considered. Many introduction guidelines show that the animal will be habituated to the environment and in some cases directly being added to the group.

I’m wondering if anybody has ever thought about a different way? Or is it one of those things where we say for each species “we’ve always done it this way, so why change it, it works”.

Introduction of 2 European Bisons:

At Kolmårdens Wildlife Park we used to have 5 European bison. A nice group with a beautiful male named Bork. The exhibit doesn’t allow the keepers to easily gate the animals from area to area. The keepers came up with a solution to teach the group of bison to be called over on a signal wherever the keepers would be. This allowed them to efficiently move the animals around at any given time in the day.

The beautiful thing about this type of strategy is that we are now able to apply an enrichment programme. It also means the vet doesn’t have to go into the exhibit anymore to look at the animals and when we have to dart an animal, we can ask all other animals off exhibit, directly after the one animal is darted. Another pro with training this behaviour is the time we get back from shifting animals.

Recently Kolmårdens Wildlife Park received 2 new European bison. We put the new bison almost directly into the herd. At the start, there were some complications but that settled very quickly. One of the key ingredients of the introduction was the call over that was trained to the herd, previous to the arrival of the new bison. We had some sort of behavioural control that allowed us to reinforce the animals to be calm. On top of that, one of the criteria is “let everybody come over and receive reinforcement”.

The video above shows a proper call over at the start and one later in the video. The animals ignore each other to come over to the trainer. This way the trainers help conditioning the group being calm together. As you can see the animals are called when they are calm.

The big bull knew a bit of this criteria already. Because of the young animals in the herd, he had to accept to receive more reinforcement i.e. cooperative feeding. This was quickly established with the others as well, even though they didn’t come very close to the keepers. This was not necessarily because of the bull keeping them away but more about a new way of managing these animals. The animals were hesitant to come over.

After a while the new male came as well and joined the group. The young female still wasn’t 100% comfortable with coming to a keeper. But the group itself was very calm all together. I asked one of the keepers if the call over had an effect on the introduction and he responded right away with “YES”. One of the main reasons it worked so well was the use of cooperative feeding where the animals are learned to accept each other by the reinforcement value that is given to him when they accept one another. This has helped a lot into the introduction period.

In the marine mammal field, we use behavioural control a lot more to introduce animals to each other. When we have a new animal in a group of dolphins for example, we start by having the animals on each side of the gate. We then pick which animal in the group will be the first to come in the same area as the new animal. Most of the time this is a confident animal. We ask the confident animal to come into and come close to the new animal all in control. Then we separate them again.

These introductions are extended slowly, to a point where we get the two animals together and give them their “free time”, time without control of the trainer. This way, they can discover each other in a different way. When the animals swim calmly together, as reinforcement we call them towards us and reinforce directly. Then we add an additional animal that is closely connected to the confident animal that has just been introduced.

This helps the confidence of the new animal as well. Start off slowly, then gradually increase on a higher rate once the new animal is comfortable enough. The most important thing to remember is to be able to recognise the behaviour you want to see and use a recall to tell them ‘that was exactly what I wanted you to do’. Classical conditioning helps a lot in this case. Through this strategy an introduction of individuals goes a lot smoother and in the long run it’s a lot calmer for the group.

Introducing animals to each other is a tricky business. It’s up to us to make this as successful and stress free as possible. We can progress very far with behavioural control if we focus on what we would like to see and catch them doing it right with the timing of the reinforcer. Remember that adding reinforcers increases behaviour. Would it work all the time? Maybe. Should we look at how we can improve? Yes. Is it easier for one species compared to the other? Yes.

I believe we should always look into improving our methods and this is one of them. If we pay attention to the behaviour the animals show us are our introduction plans actually successful?

Something to think about.


Peter is a passionate Animal Consultant that beside teaching you about Operant Conditioning makes sure you will go home motivated and inspired. Make sure you read his Bio!

1 Comment

Chris Dean · December 11, 2022 at 12:58

For Peter Giljam,
Hi Peter,
The expertise and experience that you demonstrate in this article might be needed in UK if a new project comes about.
As an extension to the idea of re-wilding the Wildlife Trusts are looking at the feasibility of introducing large herbivores to UK environments. You may already be aware of this initiative.
From what I have already seen (an advert for a support officer) they are already making assumptions which won’t necessarily be true. E.g. that re-introducing a species to an environment it will naturally behave as it used to do previously thousands of years ago. That can’t be guaranteed.
Perhaps you could take an interest in their initiative and make useful comments and contributions before they make any un-resolvable mistakes.
Best wishes,
Christopher Dean

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