After some time I photographed meerkat I saw one of the unique behavior of these animals that makes me wonder. Meerkat always sunbathe in the standing position and facing toward the sun. Looks like they need sunlight to warm their bodies.
Based on information from Wikipedia I got the information that can answer my question.
The underside of the meerkat has no markings, but the belly has a patch which is only sparsely covered with hair and shows the black skin underneath. The meerkat uses this area to absorb heat while standing on its rear legs, usually early in the morning after cold desert nights