Pigs' love of mud linked to their evolution: Study

It is well known that pigs wallow in mud to keep cool because they do not have normal sweat glands to regulate their body temperature.

But a scientist in the Netherlands has revealed that the animals' love of mud is more than just a way to cool them.

Marc Bracke from Wageningen University and Research Centre suggested that the behaviour could have evolved in pigs' most ancient relatives.

"We all evolved from fish, so it could be that this motivation to be in water could be something that was preserved in animals that are able to do so," BBC quoted Bracke as saying.

For his study, Bracke looked at wallowing behaviour in pigs' wild relatives to find out more about what motivates the animals to luxuriate in sludge.

He examined closely related "wallowers", including hippos, which spend their time in water to keep cool.

He thinks that pigs did not evolve functional sweat glands like other ungulates because they liked wallowing so much.

Bracke also proposed that mud wallowing, like rolling, could play a role in reproduction in pigs.

The study was published in the journal Applied Animal Behaviour Science.