cathemerality

In the original manuscript for his article "Patterns of activity in the Mayotte lemur, Lemur fulvus mayottensis," Ian Tattersall introduced the term cathemerality to describe a pattern of observed activity that was neither diurnal nor nocturnal.{{Sfn|Tattersall|1979}} 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 roots.

The word is a compound of two Greek terms: {{Lang|grc|κᾰτᾰ́}} ({{Lang|grc-Latn|katá}}) 'through' and {{Lang|grc|ἡμέρᾱ}} ({{Lang|grc-Latn|hēmérā}}) '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.{{Sfn|Tattersall|1987}}

File:Common brown lemur (Eulemur fulvus) male.jpg

Photoperiodism 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 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.{{Cite journal|last=Mutschler|first=Thomas|date=2003-01-07|title=Alaotran gentle lemur: Some aspects of its behavioral ecology|url=http://dx.doi.org/10.1002/evan.10068|journal=Evolutionary Anthropology: Issues, News, and Reviews|volume=11|issue=S1|pages=101–104|doi=10.1002/evan.10068|s2cid=85213958|issn=1060-1538}} 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.{{Cite journal|last1=Clarke|first1=JL|last2=Jones|first2=ME|last3=Jarman|first3=PJ|date=1995|title=Diurnal and Nocturnal Grouping and Foraging Behaviors of Free-Ranging Eastern Grey Kangaroos|url=http://dx.doi.org/10.1071/zo9950519|journal=Australian Journal of Zoology|volume=43|issue=5|pages=519|doi=10.1071/zo9950519|issn=0004-959X}}

File:Siganus lineatus.jpg

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 an attempt to minimize the risk of predation, lemurs limit their amount of diurnal activity. Predation masking effects have also been exhibited by the golden-lined spinefoot (Siganus lineatus), a tropical reef fish, which shifts its activity based on specific predation pressures in specific environments.{{Cite journal|last1=Fox|first1=Rebecca J.|last2=Bellwood|first2=David R.|date=2011-06-06|title=Unconstrained by the clock? Plasticity of diel activity rhythm in a tropical reef fish, Siganus lineatus|journal=Functional Ecology|volume=25|issue=5|pages=1096–1105|doi=10.1111/j.1365-2435.2011.01874.x|issn=0269-8463|doi-access=free|bibcode=2011FuEco..25.1096F }} 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.

It has been reported that body size is correlated with cathemeral behaviour.{{Cite journal|last1=van Schaik|first1=Carel P.|last2=Griffiths|first2=Michael|date=1996|title=Activity Periods of Indonesian Rain Forest Mammals|url=http://dx.doi.org/10.2307/2388775|journal=Biotropica|volume=28|issue=1|pages=105|doi=10.2307/2388775|jstor=2388775|bibcode=1996Biotr..28..105V |issn=0006-3606}} 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.{{Citation|last=Halle|first=Stefan|title=Ecological Relevance of Daily Activity Patterns|date=2000|url=http://dx.doi.org/10.1007/978-3-642-18264-8_5|work=Activity Patterns in Small Mammals|series=Ecological Studies|volume=141|pages=67–90|place=Berlin, Heidelberg|publisher=Springer Berlin Heidelberg|doi=10.1007/978-3-642-18264-8_5|isbn=978-3-642-62128-4|access-date=2021-11-10}}

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.{{Cite journal|last=Kirk|first=E. Christopher|date=2006|title=Eye Morphology in Cathemeral Lemurids and Other Mammals|url=http://dx.doi.org/10.1159/000089694|journal=Folia Primatologica|volume=77|issue=1–2|pages=27–49|doi=10.1159/000089694|pmid=16415576|s2cid=13081411|issn=0015-5713}} 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.{{Cite journal|last=Tattersall|first=Ian|date=2008|title=Avoiding commitment: cathemerality among primates|url=http://dx.doi.org/10.1080/09291010701683292|journal=Biological Rhythm Research|volume=39|issue=3|pages=213–228|doi=10.1080/09291010701683292|bibcode=2008BioRR..39..213T |s2cid=84317327|issn=0929-1016}}

{{Wiktionary|cathemeral}}

• Diurnality
• Nocturnality
• Crepuscular
• Crypsis

{{reflist|3}}

• {{cite journal |last1=Tattersall |first1=I. |title=Patterns of Activity in the Mayotte Lemur, Lemur fulvus mayottensis |journal=Journal of Mammalogy |date=29 May 1979 |volume=60 |issue=2 |pages=314–323 |doi=10.2307/1379802|jstor=1379802 }}
• {{cite journal |last1=Tattersall |first1=Ian |title=Cathemeral Activity in Primates: A Definition |journal=Folia Primatologica |date=14 February 1987 |volume=49 |issue=3–4 |pages=200–202 |doi=10.1159/000156323}}

{{Ethology}}

{{Light Ethology}}

Category:Ethology