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Sleep can follow a physiological or behavioral definition. In the physiological sense, sleep is a state characterized by reversible unconsciousness, special brainwave patterns, sporadic eye movement, loss of muscle tone (possibly with some exceptions; see below regarding the sleep of birds and of aquatic mammals), and a compensatory increase following deprivation of the state, this last known ...
Crepuscular, a classification of animals that are active primarily during twilight, making them similar to nocturnal animals. Diurnality, plant or animal behavior characterized by activity during the day and sleeping at night. Cathemeral, a classification of organisms with sporadic and random intervals of activity during the day or night.
Unique type of brown adipose tissue, allowing mammals to generate heat quickly. [10] Mitochondria with respiration rates five to seven times higher than those of reptiles of similar size. [11] Fur to assist in thermo-regulation in a cold (night) environment. Lack of an ocular shielding mechanism against (diurnal) ultraviolet light. [12]
The hippopotamus sleeps with both hemispheres of the brain resting, as in all land mammals, and usually sleeps on land or in water with the nostrils exposed. Despite this, it may be capable of sleeping while submerged, intermittently surfacing to breathe without waking.
The American pygmy shrew is the smallest mammal native to North America and is one of the smallest mammals in the world, just slightly larger than the Etruscan shrew of Eurasia. Its body is about 5 cm (2 in) long including a 2-cm-long tail, and it weighs about 2.0 to 4.5 g (0.07 to 0.16 oz). [ 9 ]
The kiwi is a family of nocturnal birds endemic to New Zealand.. While it is difficult to say which came first, nocturnality or diurnality, a hypothesis in evolutionary biology, the nocturnal bottleneck theory, postulates that in the Mesozoic, many ancestors of modern-day mammals evolved nocturnal characteristics in order to avoid contact with the numerous diurnal predators. [3]
Holtze, who specializes in assisted reproduction in animals, said that the information they uncovered during the study would help with her work to come up with a way to artificially inseminate bats.
The distinction is not absolute, because crepuscular animals may also be active on a bright moonlit night or on a dull day. Some animals casually described as nocturnal are in fact crepuscular. [2] Special classes of crepuscular behaviour include matutinal, or "matinal", animals active only in the dawn, and vespertine, only in the dusk.