Watch the video above and you will see that the following dictionary definitions may need revising.

  • Swine: A person regarded as contemptible or disgusting.
  • Pig: A greedy, dirty or unpleasant person.
  • Pigsty: A very dirty or untidy house or room

In light of recent research these insults are a bit unfair. European wild boars have been observed washing dirty food before eating it.

Rather than gobbling down an apple, beetroot or piece of chicken covered with sand, the boars preferred it clean.

They carried it using their snout to the water creek that ran through their enclosure. They then swirled it around in the water before eating it.

It is a discovery that came about by chance.

Zoo keepers in Basel Zoo in Switzerland noticed that the animals had been washing their food.

Researchers followed this observation with some simple experiments. The crucial test was witnessing whether the boars transported the food in order to wash it as this requires a sophisticated level of premeditation.

To ensure they really were washing it, the researchers also gave them clean food, which the boars ate straight away.

The boars were also deprived of food in the morning. This made it even more difficult to resist eating the food immediately.

Even then, they held off the temptation to eat the food before it was clean.

One of the male boars even used his own spit to wash sand off his apples.

"This was hilarious, he was too lazy to go to the water," says Adriana Lowe from University College London, one of the co-authors of the study in the journal Animal Cognition.

They may be doing so because sandy food doesn't taste as good, she says. It ruins the texture and can even damage their teeth.

"If it is damaging teeth, it is damaging the animal's ability to process food properly," she says.

It might sound like a minor thing, she says, but if you eat lots of food with grit, an animal is taking in less calories and is going to be at an evolutionary disadvantage in the long term. 

The team don't know if this behaviour was learnt from other members of the species, or if it is widespread in other groups too.

Either way, they clearly have the cognitive ability needed to delay gratification and wait until food is more palatable, something many other animals find difficult.