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Are pigs tethered in stalls or rats kept in laboratory cages bored?
In Britain today, as many as half of the pregnant sows are tethered or housed
in stalls. Here they frequently show abnormal ‘stereotypic behaviour’ such
as biting the bars of their stalls and chewing their chains. Such behaviours
have no apparent function and are repeated over and over again in the same
form, sometimes for hours at a time. Are they signs of boredom?

Physiological studies, particularly at the University of Wageningen
in the Netherlands and at the National Institute for Agricultural Research
in Bordeaux in France, have confirmed the intuitive impression that this
strange behaviour shows that something is wrong: stereotypic behaviour is
associated with stressful conditions. But stressful in what way? Until recently,
the most common explanation was boredom. The environment is barren and it
was said that the pigs did not have enough stimulation. One theory about
stereotypies, in fact, is that they are performed to increase general stimulation:
in other words, to dispel boredom.

Studying the behaviour of sows in Edinburgh, Alistair Lawrence and I
felt that this theory was unsatisfactory. We wondered what sort of stimulation
was important to these animals. Sows varied considerably in how much stereotypic
behaviour they showed. What caused this variation?

We found that a major cause of stereotypies in tethered sows is food
restriction. Sows allowed to eat as much as they like become fatter than
the farmer wants, so their food is restricted to prevent this. On high food
allowances, none of the pigs showed many stereotypies. On low allowances,
behaviour was variable, but many of the animals carried out a considerable
amount of this behaviour.

Pigs in the wild do not get unlimited food, yet they do not show stereotypic
behaviour. The same applies to more familiar animals, such as pet dogs.
The difference is that free-ranging animals can search for food, even if
they find little or none. In both confined and unconfined conditions animals
have similar expectations, of foraging and eating. But in confinement this
expectation is frustrated; they have no control over their environment.
Here, though, a specific motivation is involved, namely hunger. Our results
do not disprove the involvement of boredom, but they do suggest that a major
factor in the stereotypies of tethered sows is frustration of foraging.
It is not the only factor, and Lawrence is continuing to investigate other
causes of differences between individuals in the amount of abnormal behaviour
they show, but this sort of frustration is very important.

Our conclusion was that animals given small amounts of food should not
be confined in barren conditions and that animals in such conditions should
not be deprived of food. This conclusion has been widely quoted in the pig
farming press, and it may have contributed to recent moves in Parliament
to ban this sort of housing for sows altogether.

It is not only pigs that suffer frustration of foraging. Horses in
stalls on concentrated diets also show stereotypic behaviour, such as crib
biting, as do sheep kept in similar conditions for experimental purposes.
Similarly, other behaviour may be frustrated by confinement, including sexual
behaviour. Hens pace back and forward in battery cages, and the most important
reason turns out to be frustration of nesting behaviour. These stereotypies,
then, are not ‘bored games’ but symptoms of particular problems which can
be alleviated by carefully designed housing. Barry Hughes, of the Agricultural
and Food Research Council, and I are experimenting on modified cages which
allow hens to make nests and perform other specific activities. Similar
work is also being done at Bristol, as described recently by Christine Nicol
and Marian Dawkins (‘Better homes for hens’, New ÐÓ°ÉÔ­´´, 17 March 1990).
The same sort of principles are now also being applied to the design of
housing for pigs.

Stereoptypic behaviour is, of course, seen in many zoo and laboratory
animals too: polar bears pace round their enclosures, rats run endlessly
in activity wheels and voles show bizarre, repetitive leaping. There is
increasing evi-dence that these are symptoms of similar problems, and several
researchers are studying ways to improve the housing of zoo and laboratory
animals through ‘environ-mental enrichment’ (‘A wild time at the zoo’, New
ÐÓ°ÉÔ­´´, 5 January 1991; ‘Better homes for laboratory animals’, New ÐÓ°ÉÔ­´´,
3 December 1988).

But will there be residual problems, caused by boredom as such, which
mean that modified housing is still incompatible with welfare? And does
boredom occur in current housing systems, over and above the frustration
mentioned above? Can a pig or a hen be bored?

Ian Duncan, who works on animal welfare at the University of Guelph
in Canada, has suggested that boredom can be thought of as the frustration
of general exploration. We know from our own experience that this happens
in humans. There are two main approaches to deciding whether it occurs in
other animals too. One approach involves asking whether they will carry
out general exploration, given the opportunity. The second considers the
possible consequences of the absence of general stimulation.

The first approach, identifying general exploration, demands that we
consider situations where specific motivations such as hunger and sex are
already satisfied. Two studies of free-ranging pigs have given us considerable
knowledge of their natural behaviour: one at the University of Edinburgh
by Alex Stolba and David Wood-Gush and the other at the University of Skara
in Sweden by Per Jensen and Bo Algers. These studies suggest that, as with
so many other sorts of behaviour, the amount of general exploration varies
with age: piglets spend much more time exploring their surroundings than
adult pigs. Well-fed sows usually lie for long periods, apparently soporifically.
It is not certain whether they are bored, but I think boredom is much more
of a problem in piglets. It is logical that young animals should explore
more than adults, because they have more need to learn about their environment,
over and above looking for food or other specific stimuli.

The tendency of animals to explore their environment, and therefore
their capacity to suffer boredom if this is frustrated, probably also varies
between species. Exploration seems to be more important in primates, for
example, than in ungulates: a chimpanzee does more exploring than a grazing
antelope. Again, this makes sense, because the food of most primates is
variable and widely dispersed, as opposed to the more evenly spread diet
of grazers. Natural selection may be expected to have favoured primates
that monitored the environment extensively. On the other hand, chickens
are another species that do not apparently carry out much general exploration.

These considerations lead us to suggest that boredom as such is not
likely to be a major problem in most species of farm animals, at least in
the short term. However, it might be that in the long term frustration of
even a slight exploratory tendency could result in boredom and suffering.
This is consistent with the ideas of Francoise Wemelsfelder, a Dutch philosopher
at Leiden University who works on animal boredom. Wemelsfelder has taken
the second approach, considering the behaviour of animals kept in barren
conditions (without general stimulation) for long periods. She suggests
that a continuum exists in the feelings of confined animals, from frustration
through boredom to a further state usually called helplessness, and that
they tend to progress through this continuum over time. She points out,
for example, that when stereoptypies occur over long periods, they tend
to come progressively more fixed, more difficult to ‘cure’. Polar bears
that have established a pattern of pacing in one enclosure often continue
to follow it even if they are moved to a bigger enclosure, and horses may
carry on crib biting even when moved from a stall to a field. This suggests
that although the behaviour may originally have been caused by frustration,
the cause has changed with time. Furthermore, she suggests that this can
be tested. Where animals are frustrated, a change in their surroundings
will alter their behaviour. Where they are bored or in a state of helplessness,
any such alteration will be temporary or absent. More experimental work
in this area is obviously needed.

There is, however, an alternative explanation for the fixation of stereotypies
over time, which is that long-term frustration causes permanent neurophysiological
change. Robert Dantzer, a neurophysiologist working the National Institute
for Agricultural Research in Bordeaux, believes that higher nervous functions
are completely cut off during stereotypic behaviour, and that the behaviour
is associated with what he calls a ‘functional pathology’ of the brain.
If this is true, it would not be surprising if actual pathological changes
occur over a long period-resulting, for instance, in the regression or abnormal
sensitisation of certain processes. The 3 months that a sow is tethered
in each pregnancy and the 12 months that a hen is kept in a battery cage
are doubtless long enough for such changes to happen.

We still do not know whether nonhuman animals can be bored in the same
sense that humans experience boredom. This question may become clearer from
further work on the behaviour and physiology of farm animals. But it is
already clear that frustration can and does cause suffering in captive animals,
on the farm, in the zoo, in the laboratory or in the home. As a result of
studies on frustration, progress is possible now on important issues such
as the housing of farm animals.

Michael Appleby is a lecturer on farm animal behaviour in the University
of Edinburgh’s Institute of Ecology and Resource Management.