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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.
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