Animals sleep to

Animals that are capable of sleeping are in a behavioural and physiological state known as sleep, which is characterised by altered consciousness, decreased receptivity to outside stimuli, and homeostatic regulation. Mammals, birds, reptiles, amphibians, some fish, insects, and even more primitive creatures like nematodes have all been observed to sleep. For diurnal organisms (like humans), the internal circadian clock encourages sleep at night, while for nocturnal organisms, it does so during the day (such as rodents). Species have a wide range of sleep habits. All mammals and the majority of other species seem to need it.