View source for Nocturnal

{{about|the animal behavior of nocturnality|other uses|Nocturnal (disambiguation)}}
{{wiktionary|nocturnal}}
[[File:Northern Spotted Owl.USFWS-thumb.jpg|thumb|right|[[Owl]]s are well known for being nocturnal, although some owls are active during the day.]]
'''Nocturnality''' is an [[ethology|animal behavior]] characterized by activity during the night and sleeping during the day. The common adjective is "'''nocturnal'''".

Nocturnal creatures generally have highly developed senses of [[hearing (sense)|hearing]] and [[olfaction|smell]], and specially adapted [[eyesight]]. Some animals, such as [[cat]]s and [[ferret]]s, have eyes that can adapt to both low-level and bright day levels of illumination (see [[metaturnal]]). Others, e.g. [[bushbaby|bushbabies]] and (some) [[bat]]s, can function ''only'' at night. Many nocturnal creatures including [[tarsiers]] and some [[owls]] have large eyes in comparison to their body size in order to compensate for the lower light levels during the night. 

[[Diurnality|Diurnal]] animals, e.g. [[squirrel]]s, songbirds, etc., are active during the daytime. [[Crepuscular]] species, i.e. [[rabbit]]s, [[skunk]]s, and [[hyena]], are often erroneously referred to as nocturnal. [[Cathemeral]] species, such as [[Eupleridae|fossa]]s and [[lion]]s, are active both day and night.

==Survival adaptations==
===Resource competition===
Being active at night is a form of [[niche differentiation]], where a species' niche is partitioned not by the amount of resources but by the amount of time (i.e. temporal division of the [[ecological niche]]). [[Hawk]]s and [[owl]]s can hunt the same field or meadow for the same rodents without conflict because hawks are diurnal and owls are nocturnal. This means they are not in-competition for each other's prey.

===Predation===
Nocturnality is a form of [[crypsis]], an adaptation to avoid or enhance [[predation]]. One of the reasons that (cathemeral) [[lion]]s prefer to hunt at night is that many of their prey species ([[zebra]], [[antelope]], impala, [[wildebeest]], etc.) have poor night vision. Many species of small rodents are active at night because most of the dozen or so [[birds of prey]] that hunt them are diurnal. There are many diurnal species that exhibit some nocturnal behaviors. For example, many [[seabird]]s and [[sea turtle]]s only gather at breeding sites or colonies at night to reduce the risk of predation to themselves and/or their offspring.

===Water conservation===
Another reason for nocturnality is avoiding the heat of the day. This is especially true in [[arid]] [[biome]]s like [[desert]]s, where nocturnal behavior prevents creatures from losing precious water during the hot, dry daytime. This is an [[adaptation]] that enhances [[osmoregulation]].<ref>N.A.Campbell (1996) ''Biology'' (4th edition) Benjamin Cummings NY. ISBN 0-8053-1957-3</ref> One of the reasons that ([[cathemeral]]) lions prefer to hunt at night to conserve water.

====Plants====
{{See also|Category:Night-blooming plants}}
Many plant species native to arid biomes have adapted so that their flowers only open at night when the sun's intense heat can't wither and destroy their delicate, moist blossoms. These flowers are [[pollinate]]d by bats, another creature of the night.

==In captivity==
===Zoos===
In [[zoo]]s, nocturnal animals are usually kept in special night-illumination enclosures to invert their normal [[sleep-wake cycle]] and to keep them active during the hours when visitors will be there to see them.

===Pets===
[[Image:European hedgehog (Erinaceus europaeus).jpg|thumb|Hedgehogs are mostly nocturnal.]]
[[Hedgehog]]s and [[sugar glider]]s are just two of the many nocturnal species kept as ([[exotic pets|exotic]]) pets. Cats have adapted to domestication so that each individual, whether stray alley cat or pampered housecat, can change their activity level at will, becoming nocturnal or diurnal, to suit their environment and/or the routines of their owners.

==See also==
{{Light Ethology}}
* [[Niche (ecology)]]
* [[Niche differentiation]]
* [[Competitive exclusion principle]]
* [[Adaption]]
* [[Antipredator adaptation]]
* [[Crypsis]]
* [[List of nocturnal birds]]
* [[List of nocturnal animals]]
* [[Diurnality]]
* [[Crepuscular]]

==References==
{{reflist}}

{{commons category|Nocturnality}}

{{modelling ecosystems}}

{{Evo ecol}}

[[Category:Ethology]]