The National Zoo’s grey seals started out to be rather aggressive, but soon became trusted colleagues. We were able to routinely go in with the otters, bush dogs, beavers, cheetahs, wolves and sea lions. We worked five kinds of bears at the holding area fenceline, and were able to teach the animals to accept injections, go into travel crates and have casual examinations, in a safe and efficient way.
An aggressive animal can be dangerous to the humans working with him (it is often a male animal), but also to the other animals who live in the same area with him. If an aggressive animal is not engaged in cooperating with humans, he is free to charge people and animals, intimidating or injuring innocent animals trying to cooperate and get a job done. The aggressing animal often seems to take pleasure just in making the other animals run and show fear.
How to unravel this dilemma?
Something that has worked repeatedly for me in the past is to pay the aggressive animal, first to just sit where I ask him to, when no one else is around, and later, to sit where I ask him to, and get paid to watch other animals work. Very quickly, the aggressive animal often seems to take new pleasure in being fed and praised for the work some other animal is doing. The other animals get to learn and perform without interference, they get wonderful attention and appreciation from the audience, everyone stays safe, the audience can see the intelligence and ability of the animals in action… it is good all around!
Here is a way to start:
First, it is good to use a barrier of some type, including fences, gates, push boards and/or steel buckets. Working behind a barrier means the focus is on teaching, learning and performing, rather on that rivetting sport, ‘surviving’! It means that the animal can come close without us having to move away. He cannot injure any human, he cannot push anyone around, or try to go through their tools or pockets… it keeps the focus where it needs to be.
Secondly, one can start conditioned relaxation immediately. Since this is a no-contact situation, that means plenty of ‘Name & Explain’ (where the trainer narrates what is going on, and what WILL go on, for the animal, during the work – this relieves uncertainty and fear, and not only teaches the animal new vocabulary and new procedures, but also smooths things out!). We can name the mental state we see the animal displaying, with all its details (like, tension in the muscles and face, ear position, tail position and tail action, how the animal is looking at others – and more). We can bridge what we like. What we don’t like, we can name and ask for what is preferred (that is ‘tense’, can I have ‘easy?’). The first priority is to get the animal to be able to visibly relax on cue, which is the meaning of the cue, ‘easy’. By teaching two opposing concepts at once, the animal quickly sees how he can progress on a spectrum from one mental state, like ‘arousal’ (called ‘tense’ or ‘alert’), to a different, opposing, state (called ‘easy’). With animals that are safe to touch, massage is usually the main reinforcer for this exercise. However, with untouchable animals, food, games, and other things can be used to reward the animal’s efforts to master relaxation (easy).
It may be very effective to stop all training of all animals except the dominant aggressive animal, initially. Until he is cooperative, the dominant animal is likely to charge and threaten all subordinate animals, causing them distress, or even injury, and teaching them not to get involved in training, or even coming near trainers.
Once the animal is making progress in changing his mental state, on request, we can start on target training. In particular, it is useful to teach an animal to stay at a target station, for expanding lengths of time. This helps the animal to progress in relaxation, and it teaches him patience.
When the animal shows a willingness to relax on request, AND will target for extended durations on his target station, as asked, then he is ready to learn to maintain his calm station, even when other animals come into the exhibit. The first animal to add could be a confident, favored female – like a favorite mate. Regardless of how well the first animal likes the second, he is not encouraged to go anywhere near the new animal. He is paid to act as if they are not there. So, I may start by helping the aggressive animal to keep his focus away from the new animal, but soon, I will encourage him to watch the other animal calmly, while staying on his target station. If he breaks that request, the second animal can be instantly released from training, and the trainer can retreat. This takes away all the chance for confrontation, control and TREATS. This process usually gets things going in the right direction quickly. One can use ‘Cycles’ to introduce the second animal. That is to say, the animal does not just get added to the common area with the aggressive animal. Instead, he is brought in for an instant, brought back out again, and then, with no other animal to distract him, the aggressive animal is helped to relax again. In the next Cycle, the second animal comes in longer, or further, the retreats again, and then we work on relaxation again. And so it goes, until the first animal can calmly watch the second animal work and get treats and applause, without getting aroused, violent, or even moving from his seat.
The same process can be repeated with a different, single, animal. Once objectives are met, the cycles start with a third animal, and so on, until all the animals have been introduced singly.
We can repeat the process, working pairs of animals, to the same end result.
Then threesomes.
Then quartets.

Dogs studying ‘Conditioned Relaxation’. They are doing quite well!
Etc, till all the animals can work at once.
Then it can be good to increase the span of time the animals can work together, starting with a very short time, but approximately doubling the time of each trial, until time is no object.
If there are other important variables to teach the animals to cope with, this is the time to identify each of those, and systematically introduce each, till the animals master their ability to cope with each challenge.
If at any time, the aggressive animal breaks target/place, all training stops and stations become ‘inactive’ (no one gets reinforced for being on target). This robs the animal of getting to attack the others, human or animal.
During the learning phase where the aggressive animal is to stay on station while the other animal are brought onto station and then removed, there are a number of ways to manage this, including posting a trainer by each animal station with a means of protecting themselves and the animal – like a push board. However, I don’t do this if I am not confident that the aggressive animal can be easily, safely stopped. If we are behind a barrier, it is easy to just end the training until the animal returns to his station and stays there for a bit, then we can will try again.
The topography of the exhibit is important. For example, at National Zoo, we had from 7-9 sea lions together. I put Norman, the dominant male, at one end of the pool, on an island. The other animals, all females, were either 100 feet away on other islands/bluffs, or right next to us on the beach. Norman’s trainer (me) was well away from the other females, and the other trainers. So, if Norman ‘broke station,’ the females and other trainers had plenty of time to retreat before Norman arrived to raise havoc. And, I was always ready to toss fish to reward him for staying on station, at the instant he noticed the females arrival.
In this case, the male would aggress against the females, but was unlikely to attack the humans. However, it was as important to protect the females as to protect the humans.
One can would use similar tactics with an animal which is aggressive toward humans, but should first ask, do I really need to be in direct contact?
If not, train, and work, from behind a barrier. If there really is a need to be in direct contact, find an equalizer. An ‘equalizer’ is some tool that allows the trainer to be safe when in the proximity of the aggressive animal. It can be as simple as vinegar in a spray bottle, pepper spray, a fire extinguisher, or a horse whip. I show the animal what these tools are, and how they are used, and then I use them defensively, In other words, I don’t chase a male around the exhibit with a vinegar spray bottle to show him who is boss (maybe him!), but I will use the bottle to protect my perimeter. Of course, the defensive measure must be appropriate for that animal and that situation, and it is best to work with another trainer, in case of mishap..
For example, when it is necessary to take a horse from a paddock filled with multiple horses, it can be difficult, initially, to quickly and safely remove just one horse, without the other horses storming the gate. To solve this problem, one can first show the animals that a whip establishes a 10 foot ‘clear zone’ around the trainer. So when the trainer approaches, before the horses even move toward the gate, he can call out ‘clear!’. When I have done this protocol, I start 10 ft away from the gate and call ‘clear!’, walking forward slowly toward the gate, twirling the whip overhead like the blades of a helicopter. As the animals stop and back away, I instantly stop, praise them and back away also. I want them to see that they have the power to control me. The more they move away from me, the more I move away from them. Then I ask for ‘clear’ again, and start to walk forward. The other animals usually back away much more readily the second time. By the third or fourth trial, they usually just stay 10 feet away and leave the gate alone when I call out ‘clear’. I then like to systematically teach each animal how to approach, and walk with me, as the whip twirls overhead. I usually start with the animal right next to me, and start the whip twirling perpendicular to the ground, on the far side of me, away from the animal. I start with very short twirls, but quickly work up to the animal standing calmly with me, as the whip twirls overhead. Then we start to move together. Finally, I teach the animal to come in under the whip, and leave under the whip. Now, the animal has learned that (s)he is safe, as long as their name has been called to approach. I have not had to touch a horse with the whip. I just show them that I could. Each animal is confident in knowing that he is to stay in, or come along with me. Whichever it is, he knows how to stay safe and comfortable and correct (with all the praise and rewards that come with being correct!
If the animal is aggressive toward the trainers, it is possible to introduce the trainers exactly as the animals were introduced. To increase safety, we can arm the trainers with equalizers/deterrents, and even give them safe zones to work from and retreat to. I have put trainers in holding cages, adjoining the main yard, with whips/spray bottles, so they can work from these ‘safe zones’ toward the unprotected zone. As with the animals, if the aggressive animal breaks station, the trainers all retreat, and there is no drama.
It is very strategic to prevent drama. Boring is good. Very good.
This training process has been put to the test with many groups of animals of many different species, including all my animals at the National Zoo, and various primates, herd animals, ducks, pigs, horses and more. We can see a big difference in group interactions, even in a single day. In fact, we can really change the confidence levels of the animals involved. When subordinate animals get a chance to shine without fear, they become more confident and more successful.
The aggressive animal gets paid for staying on station, particularly when the other animals or people, come to their stations, or otherwise enter the area. He gets paid for the work the other animals do. He usually quickly starts to take a proprietary perspective on the other animals working, and seems to bask in the fact that when they work, he gets paid for nothing!
Most animals quickly learn to appreciate being paid for nothing. Life is good!