Question

why do some of the animals like pigs toil in the mud during hot summer?

Answer 1

To make their body cool.

Answer 2

Pigs lack functional sweat glands and are almost incapable of panting. ... While many have suggested that pigs wallow in mud because of a lack of sweat glands, pigs and other wallowing animals may have not evolved functional sweat glands because wallowing was a part of their behavioural repertoire.