Male sloths are solitary, shy animals. Female sloths sometimes congregate together. Sloths are nocturnal, they are most active at night and sleep all day. They sleep about 15 to 18 hours each day, hanging upside down. Sloths move only when necessary and even then very slowly. The sloth’s nature allows it to conserve energy, moving slower than any other mammal on the planet. This modest pace means that sloths generally travel no more than 125 feet (38 meters) in a single day, and on the rare occasion that they find themselves at ground level, they crawl only 1 foot (30 cm) per minute. The facial structure of a sloth gives the appearance that it is constantly smiling – even if it is experiencing pain, stress, or anxiety. When sloths are used as a photo prop for wildlife selfies, tourists may accidentally confuse this feature for happiness or contentment.