No way out

Effect of caging on animals

source: Andrea Lord
New Scientist January 26 2002
starts p34, 5 pages long

Stereotypies are repetitive rituals performed by caged animals, and some humans also carry out repetitive actions. Stereotypies are often symptoms of mental disorders, when performed by humans. Both animals and humans which have been given amphetamines can exhibit stereotypies. Tests on animals have shown that those exhibiting stereotypies in captivity tend to persist in inappropriate behaviour outside their cages. Parrots, blue tits and voles were given food rewards for looking in a certain place. When the food was removed and put elsewhere, those with stereotypies did not learn to look somewhere new, but instead carried on looking where the food used to be.

Caged animals suffer stress because they are unable to respond to their instincts, like stalking, or burrowing. Stress resulting from a caged environment may affect brain chemistry and neurotransmitters in the brain, according to University of California’s Joe Garner, who carried out the tests, with University of Oxford’s Georgia Mason. These changes in the brain may prevent caged animals from reacting to environmental changes. Younger animals are less affected, and their stereotypies may cease after an improvement in the environment. Durham University’s Michelle Turner is a specialist in autism, and also sees parallels between some types of human and animal repetitive behaviour.

Brain damage is not, however, always the cause of stereotypies. University of Lincoln’s Daniel Mills has found that horses can be cured of long-term stereotypies that have lasted 12 years, by putting a mirror in their stables, so he doubts that brain pathology is involved. Brain damage may result from extreme conditions, which are counter to those that an animals has evolved to deal with, or when the animal’s development has been affected at a critical time, Mills argues. Mason likewise sees some severe animal stereotypies as linked to brain damage, but only those which are irreversible.

There is a case for enriching the environment that animals are kept in. Stereotyping animals often hurt themselves. Tests to study the behaviour of laboratory animals are also likely to be invalid if the animals have been driven mad by their environment.