Only recently has there been enough data on the longevity of wild animals to establish whether animals live longer in captivity or in the wild.
A study of more than 50 mammal species found that, in over 80 per cent of cases, zoo animals live longer than their wild counterparts.
In terms of lifespan, at least, it seems that the protection afforded by zoos against predators, disease and the elements outweighs any social and behavioural problems arising from life in captivity.
The effect was most pronounced in smaller species with a faster pace of life. Larger, slower species with few predators, such as elephants, live longer in the wild.
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