In zoology, a crepuscular animal is one that is active primarily during the twilight period, [1] being matutinal, vespertine/vespertinal, or both. This is distinguished from diurnal and nocturnal behavior, where an animal is active during the hours of daytime and of night, respectively. Some crepuscular animals may also be active by moonlight or during an overcast day. Matutinal animals are active only after dawn, and vespertine only before dusk.
A number of factors affect the time of day an animal is active. Predators hunt when their prey is available, and prey try to avoid the times when their principal predators are at large. The temperature may be too high at midday or too low at night. [2] Some creatures may adjust their activities depending on local competition.
The word crepuscular derives from the Latin crepusculum ("twilight"). [3] Its sense accordingly differs from diurnal and nocturnal behavior, which respectively peak during hours of daytime and night. 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. Those active during both times are said to have a bimodal activity pattern.
The various patterns of activity are thought to be mainly antipredator adaptations, though some could equally well be predatory adaptations. [4] Many predators forage most intensively at night, whereas others are active at midday and see best in full sun. The crepuscular habit may both reduce predation pressure, increasing the crepuscular populations, and offer better foraging opportunities to predators that increasingly focus their attention on crepuscular prey until a new balance is struck. Such shifting states of balance are often found in ecology.
Some predatory species adjust their habits in response to competition from other predators. For example, the subspecies of short-eared owl that lives on the Galápagos Islands is normally active during the day, but on islands like Santa Cruz that are home to the Galapagos hawk, the owl is crepuscular. [5] [6]
Apart from the relevance to predation, crepuscular activity in hot regions also may be the most effective way of avoiding heat stress while capitalizing on available light.
Crepuscular flight activity is preferred by some animals, such as the walnut twig beetle, due to warmer temperatures, moderate wind speeds, and low barometric pressure. [7]
Crepuscular activity can be influenced by the lunar cycle due to the change in nocturnal light. This creates changes in animal sleep, reproduction, and foraging behaviours, often becoming less active during periods of low light. [8]
Animal patterns of activity sometimes change during migration due to changes in environmental conditions. Mule deer are crepuscular, but they are only active at dusk before and during migration. In the spring they are only active at dawn because the snow is at its hardest, so it is easier for the deer to move without sinking in the snow. [9]
During migration, some types of swallow are active primarily during daytime hours with some activity during twilight hours. [10]
Crepuscular animal activity is affected by human activity, because humans are diurnal. Crepuscular animals are less likely to participate in typical foraging or reproductive behaviors and deal with increased stress and mortality rates when humans are present. [11] Animals may change their usual activity patterns in response to the presence of humans. For example, Asian black bears may avoid areas with high human activity during the day, but go to these locations during twilight or nighttime hours. [12]
Light pollution impacts crepuscular behaviour because it mimics natural light conditions, leading crepuscular animals to behave as they would on nights with more moonlight. [8]
Many familiar mammal species are crepuscular, including the endangered Amazon river dolphin, some species of bats, [2] hamsters, housecats, stray dogs, [13] rabbits, [2] ferrets, [14] rats, [15] jaguars, ocelots, bobcats, servals, strepsirrhines, red pandas, bears, [16] deer, [2] [17] moose, sitatunga, capybaras, chinchillas, the common mouse, skunks, squirrels, foxes, wombats, wallabies, quolls, possums [2] and marsupial gliders, tenrecs, and spotted hyenas.
Snakes, lizards, and frogs, [18] especially those in desert environments, may be crepuscular. [2]
Crepuscular birds include the common nighthawk, barn owl, [19] owlet-nightjar, chimney swift, American woodcock, spotted crake, white-breasted waterhen, [20] European nightjars, [8] and common buzzards. [21]
Many moths, beetles, flies, and other insects are crepuscular and vespertine.[ citation needed ] For example, Coprophanaeus ensifer, a South American necrophagous beetle, is most active during at dusk and dawn. [22]
Night monkeys, also known as owl monkeys or douroucoulis, are nocturnal New World monkeys of the genus Aotus, the only member of the family Aotidae. The genus comprises eleven species which are found across Panama and much of South America in primary and secondary forests, tropical rainforests and cloud forests up to 2,400 metres (7,900 ft). Night monkeys have large eyes which improve their vision at night, while their ears are mostly hidden, giving them their name Aotus, meaning "earless".
Nocturnality is a behavior in some non-human animals characterized by being active during the night and sleeping during the day. The common adjective is "nocturnal", versus diurnal meaning the opposite.
The common degu, or, historically, the degu, is a small hystricomorpha rodent endemic to the Chilean matorral ecoregion of central Chile. The name degu on its own indicates either the entire genus Octodon or, more commonly, just the common degu. Common degus belong to the parvorder Caviomorpha of the infraorder Hystricognathi, along with the chinchilla and guinea pig. The word degu comes from the indigenous language of Chile, Mapudungun, and the word dewü, meaning 'mouse' or 'rat'.
An endotherm is an organism that maintains its body at a metabolically favorable temperature, largely by the use of heat released by its internal bodily functions instead of relying almost purely on ambient heat. Such internally generated heat is mainly an incidental product of the animal's routine metabolism, but under conditions of excessive cold or low activity an endotherm might apply special mechanisms adapted specifically to heat production. Examples include special-function muscular exertion such as shivering, and uncoupled oxidative metabolism, such as within brown adipose tissue.
Biological rhythms are repetitive biological processes. Some types of biological rhythms have been described as biological clocks. They can range in frequency from microseconds to less than one repetitive event per decade. Biological rhythms are studied by chronobiology. In the biochemical context biological rhythms are called biochemical oscillations.
Vespertine is a term used in the life sciences to indicate something of, relating to, or occurring in the evening. In botany, a vespertine flower is one that opens or blooms in the evening. In zoology, the term is used for a creature that becomes active at dusk, such as bats and owls. Strictly speaking, however, the term means that activity ceases during the hours of full darkness and does not resume until the next evening. Activity that continues throughout the night should be described as nocturnal.
Deilephila elpenor, the elephant hawk moth or large elephant hawk moth, is a moth in the family Sphingidae. Its common name is derived from the caterpillar's resemblance to an elephant's trunk. It is most common in central Europe and is distributed throughout the Palearctic region. It has also been introduced in British Columbia, Canada. Its distinct olive and pink colouring makes it one of the most recognisable moths in its range. However, it is quite easy to confuse the elephant hawk moth with the small elephant hawk moth, a closely related species that also shares the characteristic colours.
Cathemerality, sometimes called "metaturnality", is an organismal activity pattern of irregular intervals during the day or night in which food is acquired, socializing with other organisms occurs, and any other activities necessary for livelihood are undertaken. This activity differs from the generally monophasic pattern of nocturnal and diurnal species as it is polyphasic and is approximately evenly distributed throughout the 24-hour cycle.
Diurnality is a form of plant and animal behavior characterized by activity during daytime, with a period of sleeping or other inactivity at night. The common adjective used for daytime activity is "diurnal". The timing of activity by an animal depends on a variety of environmental factors such as the temperature, the ability to gather food by sight, the risk of predation, and the time of year. Diurnality is a cycle of activity within a 24-hour period; cyclic activities called circadian rhythms are endogenous cycles not dependent on external cues or environmental factors except for a zeitgeber. Animals active during twilight are crepuscular, those active during the night are nocturnal and animals active at sporadic times during both night and day are cathemeral.
Diel vertical migration (DVM), also known as diurnal vertical migration, is a pattern of movement used by some organisms, such as copepods, living in the ocean and in lakes. The adjective "diel" comes from Latin: diēs, lit. 'day', and refers to a 24-hour period. The migration occurs when organisms move up to the uppermost layer of the water at night and return to the bottom of the daylight zone of the oceans or to the dense, bottom layer of lakes during the day. DVM is important to the functioning of deep-sea food webs and the biologically-driven sequestration of carbon.
In the study of chronobiology, entrainment refers to the synchronization of a biological clock to an environmental cycle. An example is the interaction between circadian rhythms and environmental cues, such as light and temperature. Entrainment helps organisms adapt their bodily processes with the timing of a changing environment. For example, entrainment is manifested during travel between time zones, hence why humans experience jet lag.
The Southern African vlei rat is a species of rodent in the vlei rat genus, Otomys, of the family Muridae in the order Rodentia. This is the type species of the genus. It is native to the grasslands and swamps of southern Africa where it is a common species.
The Java mouse-deer is a species of even-toed ungulate in the family Tragulidae. When it reaches maturity it is about the size of a rabbit, making it the smallest living ungulate. It is found in forests in Java and perhaps Bali, although sightings there have not been verified.
Matutinal, matinal, and matutine are terms used in the life sciences to indicate something of, relating to, or occurring in the early morning. The term may describe the morning activities of crepuscular animals that are significantly active during the predawn or early hours and which may or may not then be active again at dusk, in which case the animal is also said to be vespertinal/vespertine. During the morning twilight period and shortly thereafter, these animals partake in important tasks, such as scanning for mates, mating, and foraging.
Vision is the most important sense for birds, since good eyesight is essential for safe flight. Birds have a number of adaptations which give visual acuity superior to that of other vertebrate groups; a pigeon has been described as "two eyes with wings". Birds are theropods, and the avian eye resembles that of other sauropsids, with ciliary muscles that can change the shape of the lens rapidly and to a greater extent than in the mammals. Birds have the largest eyes relative to their size in the animal kingdom, and movement is consequently limited within the eye's bony socket. In addition to the two eyelids usually found in vertebrates, bird's eyes are protected by a third transparent movable membrane. The eye's internal anatomy is similar to that of other vertebrates, but has a structure, the pecten oculi, unique to birds.
Chapman's zebra, named after explorer James Chapman, is a subspecies of the plains zebra from southern Africa.
Diplodactylus vittatus, commonly known as the eastern stone gecko, stone gecko, and wood gecko, is a species of diplodactylid lizards that occurs in forest, shrubland and arid regions across Australia. It is widespread across the states of Queensland, Victoria and New South Wales, commonly found in dry peripheral bushlands. This gecko can be kept as a pet or seen within zoo enclosures.
Whether fish sleep or not is an open question, to the point of having inspired the title of several popular science books. In birds and mammals, sleep is defined by eye closure and the presence of typical patterns of electrical activity in the brain, including the neocortex, but fish lack eyelids and a neocortex. Some species that always live in shoals or that swim continuously are suspected never to sleep. There is also doubt about certain blind species that live in caves.