So I wondered if some animals need to spend time and energy on voluntary exercise so that they are fit enough to out-run predators, win over mates or hunt down prey," he explains.

The trend of breeding animals to make them more attractive even when it damages their health has spread to horses, vets are warning, after a stable released images showing a ‘cartoon-like’ colt.

For some animals, maintaining fitness comes at little to no effort. Polar bears and penguins burn different tissues while fasting, the researcher points out, not from doing voluntary exercise.

The cartoon European rabbit is certainly a little more rounded out and humanized then her real-life counterpart. However, Judy does have the rabbit's characteristic long ears and short, fluffy tail.

In humans, these changes are induced by exercise. In animals such as bears and migratory birds, they appear to be triggered by seasonal changes that alert their bodies to a coming challenge.

Exercise makes it easier to bounce back from too much stress, according to a fascinating new study with mice. It finds that regular exercise increases the levels of a chemical in the animals ...