May 2, 2011
Mud Is More Than Cooling For Pigs
To find out what motivates pigs to frolic around in the mud, a scientist in the Netherlands looked at the wallowing behavior of its wild relatives.
Marc Bracke from Wageningen University and Research Centre carried out the study that suggests a pig's love of mud is not just a way to keep cool, but is vital for the animals' well-being.
Pigs are known to wallow in order to keep cool because they do not have normal sweat glands to regulate their body temperature.
Bracke searched through scientific literature for any evidence of what might motivate other animals to carry out the similar behavior.
He looked at animals such as the hippo, a pig's close relative, who spend much of their time in the water in order to keep cool; and the deer because they roll around on the ground, not to keep cool, but to "scent mark" in order to attract a mate.
From these analyses, Bracke proposed that mud wallowing, similar to rolling, may be hardwired in pigs and could play a role in their reproduction.
"If so, wallowing could be an important element of a good life in pigs," says Bracke.
Bracke also suggests that the rolling behavior of pigs was possibly evolved from its ancient relatives.
"Pigs are genetically related to particularly water-loving animals such as hippos and whales," Bracke says.
"It seems to me that this preference to be in shallow water could have been a turning point in the evolution of whales from land-dwelling mammals," he adds.
Watering holes are ideal places for predators to ambush their prey, and for many animals wallowing would be dangerous.
"But pigs, like many carnivores, are relatively large animals with enlarged canine teeth, so they would be better able to fend off an attack," says Bracke.
In conclusion, Bracke thinks that pigs "did not evolve functional sweat glands like other ungulates because they liked wallowing so much," and not because they need the mud to cool down because pigs do not have [functional] sweat glands.
The study is published in the journal Applied Animal Behaviour Science.
On the Net: