The welfare of exotic animals in captive environments has been the focus of many applied ethology studies that have explored the relationship between physiological stress, abnormal behaviours and sub-optimal environments. This has led to a healthy cross-fertilization between ethologists working with farm animal and those working with exotic animals.
There are a number of ways of improving a sub-optimal environment. These include:
Behavioural enrichment. The overarching aim of this method of enrichment is to create an environment that mimics the animal’s wild habitat and allows it to express all its natural behaviours. For example, we might enhance the environment of large cats in a zoo by providing them with masses of vegetation typical of their environmental niche, a pool, or a hunting area. In the strictest sense behavioural enrichment requires an extremely diverse environment and consequently a large amount of space, but this is prohibitively expensive. Equally, we have to acknowledge that allowing an animal to ‘express all its natural behaviours’ is not the full story. If it were, it would mean that we would have to allow predatory species to kill their prey. Equally for prey species, we would have to let them express their natural fear. So, there must be limits on the extent to which full ethograms (behavioural repertoires) can be accommodated.
Conspecifics. All the domesticated species and many zoo species require companions. However, many farm, lab and zoo animals are housed individually, effectively preventing almost any social behaviour. Just think of sows in farrowing crates, calves in veal crates, horses confined to loose boxes, and solitary elephants in zoos. This social isolation is likely to lead to frustration and suffering for the animals. Placing animals in groups is one of the most easily achieved forms of environmental enrichment but this is often not implemented.
Why not? Well, there are disadvantageous consequences of placing animals in groups. For example, they may become difficult to handle or they may injure one another. Reduced productivity is another reason for this being considered unattractive by some farmers. For example, in veal calves that were kept in crates for this reason. In the case of lab animals, experimental protocol can get in the way of this sort of enrichment.
Artificial devices. Various devices have been designed for animals to ‘play’ with. Although these may have little similarity to anything that animals are likely to encounter in their natural environment, they can provide suitable enrichment if they are thought about carefully enough, e.g. see-saw arrangements for dogs in rescue shelters. Other examples of artificial appliances include radios to provide auditory stimulation or suspended chains and tyres that pigs like to destroy. The danger with these avenues of enrichment is that these appliances can become the focus of redirected behaviour patterns and precipitate the emergence of stereotypic behaviour patterns. Sometimes we also see possessiveness and defence of such resources against conspecifics. On the other hand, resources that, at first, are highly prized can lose their appeal completely as the animals becomes habituated to them.
Food-gathering activities. For visitors at zoos, feeding behaviour is often one of the most interesting and readily observed behaviours. It is not surprising, therefore, that a lot of research has been put into ways of making animals feed more naturally. The situation for farm and lab animals is different. Most of these animals are fed concentrated feeds because these maximise performance and are easier to handle when feeding large numbers of stock. This means that they consume their daily ration very rapidly. Free-ranging pigs can spend eight hours of their day foraging, but when they are fed concentrates they eat their daily allowance in 30 minutes. This leaves a large part of their day with nothing for them to do, so it is not surprising that the behaviours that arise in these circumstances are related to food. One method of reducing the tendency for these behaviours to develop is to feed concentrates in a way that makes the animal worked for them, e.g. using the Edinburgh food-ball.
Control of the environment. Lack of control of the environment is often pinpointed as a cause of frustration and stress in confined animals. When the animal cannot control things, such as the feeding time or the lighting program, and when it cannot escape from things it finds unpleasant, it often behaves in a manner that indicates frustration. If you think about a rat in a shuttle box in which the animal has learned that rewards and punishments are continually swapped around in a random fashion, you tend to find that the rat elects to stop responding. It becomes withdrawn from its environment and exhibits what is termed learned helplessness. It has lost control of its environment.
Similar syndromes can arise in pigs especially those lowest in the hierarchy of an intensively housed group. If animals are given control of some aspect of their environment, they show increased learning ability and are less aroused emotionally. Many species have been trained to control various aspects of their environment. For example, pigs have been trained to operate cold showers when the ambient temperature increases, hens will turn infrared lights on and off according to their thermal preferences, mice will turn lights on and off according to when they want to sleep. Almost all farm and laboratory species and many zoo species have been trained to perform some task to operate feeders so that they can control the timing of their meals. Giving animals control of their own environment can be a very successful way of enriching that environment. One commercial application that is gaining favour in pig farming is the electronic sow feeder.
For more information about environmental enrichment, we suggest you visit the leading web resource in this area: The Shape of Enrichment.