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 (sleeping once per day) of
nocturnal
Nocturnality is an animal behavior characterized by being active during the night and sleeping during the day. The common adjective is "nocturnal", versus diurnal meaning the opposite.
Nocturnal creatures generally have highly developed sens ...
and
diurnal species as it is polyphasic (sleeping 4-6 times per day) and is approximately evenly distributed throughout the 24-hour cycle.
![Lion waiting in Namibia](https://upload.wikimedia.org/wikipedia/commons/7/73/Lion_waiting_in_Namibia.jpg)
Many animals do not fit the traditional definitions of being strictly
nocturnal
Nocturnality is an animal behavior characterized by being active during the night and sleeping during the day. The common adjective is "nocturnal", versus diurnal meaning the opposite.
Nocturnal creatures generally have highly developed sens ...
,
diurnal, or
crepuscular
In zoology, a crepuscular animal is one that is active primarily during the twilight period, being matutinal, vespertine, or both. This is distinguished from diurnal and nocturnal behavior, where an animal is active during the hours of daylig ...
, often driven by factors that include the availability of food, predation pressure, and variable ambient temperature. Although cathemerality is not as widely observed in individual species as diurnality or nocturnality, this activity pattern is seen across the mammal taxa, such as in lions, coyotes, and lemurs.
Cathemeral behaviour can also vary on a seasonal basis over an annual period by exhibiting periods of predominantly nocturnal behaviour and exhibiting periods of predominantly diurnal behaviour. For example, seasonal cathemerality has been described for the
mongoose lemur
The mongoose lemur (''Eulemur mongoz'') is a small primate in the family Lemuridae, native to Madagascar and introduced to the Comoros Islands. These arboreal animals have pointed faces, long, bushy tails, dark-brown upper parts, pale bellies, a ...
(''Eulemur mongoz'') as activity that shifts from being predominantly diurnal to being predominantly nocturnal over a yearly cycle, but the
common brown lemur
The common brown lemur (''Eulemur fulvus'') is a species of lemur in the family Lemuridae. It is found in Madagascar and has been introduced to Mayotte.
Taxonomy
Five additional currently recognized species of lemur were until 2001 considered ...
s (''Eulemur fulvus'') have been observed as seasonally shifting from diurnal activity to cathemerality.
As research on cathemerality continues, many factors that have been identified as influencing whether or why an animal behaves cathemerally. Such factors include resource variation, food quality, photoperiodism, nocturnal luminosity, temperature, predator avoidance, and energetic constraints.
Etymology
In the original manuscript for his article "Patterns of activity in the
Mayotte lemur, ''Lemur fulvus mayottensis'',"
Ian Tattersall
Ian Tattersall (born 1945) is a British-born American paleoanthropologist and a curator emeritus with the American Museum of Natural History in New York City, New York. In addition to human evolution, Tattersall has worked extensively with lemur ...
introduced the term ''cathemerality'' to describe a pattern of observed activity that was neither diurnal nor nocturnal. Although the term ''cathemeral'' was proposed, it was initially deemed as unnecessary new jargon and thus the term ''diel'' was used in the published version instead. In 1987, Tattersall gave a formal definition of ''cathemeral'', turning to its
Ancient Greek
Ancient Greek includes the forms of the Greek language used in ancient Greece and the ancient world from around 1500 BC to 300 BC. It is often roughly divided into the following periods: Mycenaean Greek (), Dark Ages (), the Archaic peri ...
roots.
The word is a compound of two Greek terms: () 'through' and () 'day'. The term ''cathemeral'', then, means 'through the day', where "day" refers to the full day from midnight to midnight. Tattersall credits his father, Arthur Tattersall, and Robert Ireland, two classicists, for considering this lexical problem and proposing its solution.
Influences on cathemerality
![Common brown lemur (Eulemur fulvus) male](https://upload.wikimedia.org/wikipedia/commons/a/a3/Common_brown_lemur_%28Eulemur_fulvus%29_male.jpg)
Environmental factors
Photoperiodism
Photoperiodism is the physiological reaction of organisms to the length of night or a dark period. It occurs in plants and animals. Plant photoperiodism can also be defined as the developmental responses of plants to the relative lengths of light a ...
has been determined to heavily influence the distribution of activity throughout the day.
When there are increased daylight hours and increased sunset delay, afternoon activity begins earlier which, in turn, increases the amount of diurnal activity. In contrast, when there is a decrease in daylight hours and decreased sunset delay, afternoon activity begins later which, in turn, increases the amount of nocturnal activity.
Nocturnal luminosity influences the annual pattern of activity rhythms and affects both diurnal and nocturnal behaviour.
Nocturnal luminosity has been found to positively correlate with the amount of nocturnal activity and negatively correlate with diurnal activity. In other words, an animal's activity distribution may be somewhat dependent on the presence of the lunar disc and the fraction of illuminated moon in relation to sunset and sunrise times.
Thermoregulation
Thermoregulation
Thermoregulation is the ability of an organism to keep its body temperature within certain boundaries, even when the surrounding temperature is very different. A thermoconforming organism, by contrast, simply adopts the surrounding temperature ...
has been said to be an adaptive response that enables cathemeral animals to minimize thermoregulatory stress and costs associated with maintaining temperature homeostasis.
A comparison between diurnal activity and ambient temperatures showed that cathemeral individuals demonstrate the least activity during the hottest part of the day and exhibit an increase in nocturnal activity, therefore exhibit a decrease in diurnal activity during the hot wet seasons. For example, to reduce heat stress,
eastern grey kangaroos (''Macropus giganteus'') will spend hot daylight hours in the shade and as a result, they increase their nocturnal activity.
Predator avoidance
It has been hypothesized that cathemeral animals alter their activity patterns over a 24-hour period as a mechanism to avoid predation.
For example, lemurs are subject to a large amount of predation, such as from diurnal raptors or fossa, when active during the day. In attempt to minimize the risk of predation, lemurs limit their amount of diurnal activity.
Predation masking effects have also been exhibited by a tropical reef fish,
Golden-lined spinefoot
The golden-lined spinefoot (''Siganus lineatus''), also known as the goldlined rabbitfish or lined rabbitfish, is a species of marine ray-finned fish, a rabbitfish belonging to the family Siganidae. It is found in the tropical Western Pacific and ...
(''Siganus lineatus)'', which shifts its activity based on specific predation pressures in specific environments. Other hypotheses suggest that cathemerality provides less predictable activity patterns to predators, making the cathemeral individual "temporally cryptic." This provides an advantage to cathemeral animals as their predators are unable to anticipate the activity pattern of their prey due to their irregular, flexible schedule.
Energetic constraints
It has been reported that body size is correlated with cathemeral behaviour.
Cathemerality allows animals to forage for food at any point during the 24-hour day to maximize energy and nutrient intake. This implies that they have the opportunity to eat up to twice as much as nocturnal or diurnal species. Since larger animals possess larger energy requirements, they tend to spend more time foraging than smaller animals, and behave cathemerally as a result.
In contrast, small body size causes increased metabolic rate which may also result in cathemeral activity as an attempt to improve foraging efficacy, as seen in shrews and voles.
Evolution of cathemerality
The evolutionary disequilibrium hypothesis suggests that cathemerality is a result of the diversification of more specialized activity patterns, and somewhat viewed as a transition state between nocturnality and diurnality.
For example, the ancestral primate is said to be nocturnal, but may have displayed flexibility in activity patterns which facilitated the evolution of cathemerality. This hypothesis is supported by the comparative approach of vision morphology in primates.
Nocturnal primates possess visual systems that were primarily dependent on sensitivity to light as opposed to quality of acuity. Nocturnal primates also exhibit larger cornea size, high rod:cone ratio, and greater photoreceptors relative to ganglion cells when compared to diurnal primate vision systems.
Cathemeral primates exhibit a vision system that is intermediate of diurnal and nocturnal primates, which suggests an evolutionary accommodation that provided nocturnal species with the opportunity of diurnal activity when advantageous.
See also
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Diurnality
Diurnality is a form of plant and ethology, 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 a ...
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Nocturnality
Nocturnality is an animal behavior characterized by being active during the night and sleeping during the day. The common adjective is "nocturnal", versus diurnal meaning the opposite.
Nocturnal creatures generally have highly developed sens ...
*
Crepuscular
In zoology, a crepuscular animal is one that is active primarily during the twilight period, being matutinal, vespertine, or both. This is distinguished from diurnal and nocturnal behavior, where an animal is active during the hours of daylig ...
*
Crypsis
In ecology, crypsis is the ability of an animal or a plant to avoid observation or detection by other animals. It may be a predation strategy or an antipredator adaptation. Methods include camouflage, nocturnality, subterranean lifestyle and ...
References
Bibliography
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{{Light Ethology
Ethology