Cathemerality, sometimes called metaturnality, is the behaviour in which an organism has sporadic and irregular intervals of activity during the day or night in which food is acquired, socializing with other organisms occurs, and any other activities necessary for livelihood are performed. It has been defined as follows: "The activity of an organism may be regarded as cathemeral when it is distributed approximately evenly throughout the 24 h of the daily cycle, or when significant amounts of activity, particularly feeding and/or traveling, occur within both the light and dark portions of that cycle."
Many animals do not fit the traditional definitions of being strictly nocturnal, diurnal, or crepuscular, often by factors that include the availability of food, predation pressure, and variable ambient temperature. As a result, many species, particularly among primates, may be classified as cathemeral.
Alternative patterns of cathemeral activity have been observed in specific lemurs. Seasonal cathemerality has been described for the mongoose lemur (Eulemur mongoz) as activity that shifts from being predominantly diurnal to being predominantly nocturnal over a yearly cycle. The Common brown lemurs (E. fulvus fulvus) have been observed as seasonally shifting from diurnal activity to cathemerality.
In the original manuscript for his paper, "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. Though the term "cathemeral" was proposed, "a reviewer took exception to the introduction of what he regarded as unnecessary new jargon. The result was that the term 'diel' was substituted for 'cathemeral' in the published version." In 1987 Tattersall gave a formal definition of "cathemeral", turning to its Ancient Greek roots.
The word is a compound of two Greek terms: kata (κατα), meaning "through," and hemera (ήμέρα), meaning "day." Transliteration leads to "cathemeral," meaning "through the day, with 'day' meaning the full 24-hour day from midnight to midnight. Tattersall credits his father, Mr. Arthur Tattersall, and Dr. Robert Ireland, two classicists, for considering this lexical problem and proposing its solution.
The collared brown lemur (Eulemur collaris), also known as the red-collared brown lemur or red-collared lemur, is a medium-sized strepsirrhine primate and one of twelve species of brown lemur in the family Lemuridae. It is only found in south-eastern Madagascar. Like most species of lemur, it is arboreal, moving quadrupedally and occasionally leaping from tree to tree. Like other brown lemurs, this species is cathemeral (active during the day and the night; for more information please refer to Cathemerality), lives in social groups, primarily eats fruit, exhibits sexual dichromatism, and does not demonstrate female dominance. The species is listed as Endangered by the International Union for Conservation of Nature (IUCN) and is threatened primarily by habitat loss.Cryptoprocta spelea
Cryptoprocta spelea, also known as the giant fossa, is an extinct species of carnivore from Madagascar in the family Eupleridae, which is most closely related to the mongooses and includes all Malagasy carnivorans. It was first described in 1902, and in 1935 was recognized as a separate species from its closest relative, the living fossa (Cryptoprocta ferox). C. spelea is larger than the fossa, but otherwise similar. The two have not always been accepted as distinct species. When and how the larger form became extinct is unknown; there is some anecdotal evidence, including reports of very large fossas, that there is more than one surviving species.
The species is known from subfossil bones found in a variety of caves in northern, western, southern, and central Madagascar. In some sites, it occurs with remains of C. ferox, but there is no evidence that the two lived in the same places at the same time. Living species of comparably sized, related carnivores in other regions manage to coexist, suggesting that the same may have happened with both C. spelea and C. ferox. C. spelea would have been able to prey on larger animals than its smaller relative could have, including the recently extinct giant lemurs.Evolution of lemurs
Lemurs, primates belonging to the suborder Strepsirrhini which branched off from other primates less than 63 mya (million years ago), evolved on the island of Madagascar, for at least 40 million years. They share some traits with the most basal primates, and thus are often confused as being ancestral to modern monkeys, apes, and humans. Instead, they merely resemble ancestral primates.
Lemurs are thought to have evolved during the Eocene or earlier, sharing a closest common ancestor with lorises, pottos, and galagos (lorisoids). Fossils from Africa and some tests of nuclear DNA suggest that lemurs made their way to Madagascar between 40 and 52 mya. Other mitochondrial and nuclear DNA sequence comparisons offer an alternative date range of 62 to 65 mya. An ancestral lemur population is thought to have inadvertently rafted to the island on a floating mat of vegetation, although hypotheses for land bridges and island hopping have also been proposed. The timing and number of hypothesized colonizations has traditionally hinged on the phylogenetic affinities of the aye-aye, the most basal member of the lemur clade.
Having undergone their own independent evolution on Madagascar, lemurs have diversified to fill many niches normally filled by other types of mammals. They include the smallest primates in the world, and once included some of the largest. Since the arrival of humans approximately 2,000 years ago, lemurs are now restricted to 10% of the island, or approximately 60,000 square kilometers (23,000 square miles), with many facing extinction.Lemur
Lemurs ( (listen) LEE-mər) (from Latin lemures – ghosts or spirits) are mammals of the order Primates, divided into 8 families and consisting of 15 genera and around 100 existing species. They are native only to the island of Madagascar. Most existing lemurs are small, have a pointed snout, large eyes, and a long tail. They chiefly live in trees (arboreal), and are active at night (nocturnal).
Lemurs share resemblance with other primates, but evolved independently from monkeys and apes. Due to Madagascar's highly seasonal climate, lemur evolution has produced a level of species diversity rivaling that of any other primate group. Until shortly after humans arrived on the island around 2,000 years ago, there were lemurs as large as a male gorilla. Most species have been discovered or promoted to full species status since the 1990s; however, lemur taxonomic classification is controversial and depends on which species concept is used.
Lemurs range in weight from the 30-gram (1.1 oz) mouse lemur to the 9-kilogram (20 lb) indri. Lemurs share many common basal primate traits, such as divergent digits on their hands and feet, and nails instead of claws (in most species). However, their brain-to-body size ratio is smaller than that of anthropoid primates. As with all strepsirrhine primates, they have a "wet nose" (rhinarium). Lemurs are generally the most social of the strepsirrhine primates, and communicate more with scents and vocalizations than with visual signals. Lemurs have a relatively low basal metabolic rate, and as a result may exhibit dormancy such as hibernation or torpor. They also have seasonal breeding and female social dominance. Most eat a wide variety of fruits and leaves, while some are specialists. Two species of lemurs may coexist the same forest due to different diets.
Lemur research during the 18th and 19th centuries focused on taxonomy and specimen collection. Modern studies of lemur ecology and behavior did not begin in earnest until the 1950s and 1960s. Initially hindered by political issues on Madagascar during the mid-1970s, field studies resumed in the 1980s. Lemurs are important for research because their mix of ancestral characteristics and traits shared with anthropoid primates can yield insights on primate and human evolution. Many lemur species are threatened with extinction due to habitat loss and hunting. Although local traditions generally help protect lemurs and their forests, illegal logging, widespread poverty, and political instability hinder and undermine conservation efforts. Because of these threats and their declining numbers, the International Union for Conservation of Nature (IUCN) considers lemurs to be the world's most endangered mammals, noting that as of 2013 up to 90% of all lemur species face extinction within the next 20 to 25 years.Lemuridae
Lemuridae is a family of strepsirrhine primates native to Madagascar, and the Comoros Islands. They are represented by the Lemuriformes in Madagascar with one of the highest concentration of the lemurs. One of five families commonly known as lemurs. These animals were once thought to be the evolutionary predecessors of monkeys and apes, but this is no longer considered correct.Subfossil lemur
Subfossil lemurs are lemurs from Madagascar that are represented by recent (subfossil) remains dating from nearly 26,000 years ago to approximately 560 years ago (from the late Pleistocene until the Holocene). They include both living and extinct species, although the term more frequently refers to the extinct giant lemurs. The diversity of subfossil lemur communities was greater than that of present-day lemur communities, ranging from as high as 20 or more species per location, compared with 10 to 12 species today. Extinct species are estimated to have ranged in size from slightly over 10 kg (22 lb) to roughly 160 kg (350 lb). Even the subfossil remains of living species are larger and more robust than the skeletal remains of modern specimens. The subfossil sites found around most of the island demonstrate that most giant lemurs had wide distributions and that ranges of living species have contracted significantly since the arrival of humans.
Despite their size, the giant lemurs shared many features with living lemurs, including rapid development, poor day vision, relatively small brains, and female-dominated hierarchies. They also had many distinct traits among lemurs, including a tendency to rely on terrestrial locomotion, slow climbing, and suspension instead of leaping, as well as a greater dependence on leaf-eating and seed predation. The giant lemurs likely filled ecological niches now left vacant, particularly seed dispersal for plants with large seeds. There were three distinct families of giant lemur, including the Palaeopropithecidae (sloth lemurs), Megaladapidae (koala lemurs), and Archaeolemuridae (monkey lemurs). Two other types were more closely related and similar in appearance to living lemurs: the giant aye-aye and Pachylemur, a genus of "giant ruffed lemurs".
Subfossil remains were first discovered on Madagascar in the 1860s, but giant lemur species were not formally described until the 1890s. The paleontological interest sparked by the initial discoveries resulted in an overabundance of new species names, the allocation of bones to the wrong species, and inaccurate reconstructions during the early 20th century. Discoveries waned during the mid-20th century; paleontological work resumed in the 1980s and resulted in the discovery of new species and a new genus. Research has recently focused on diets, lifestyle, social behavior, and other aspects of biology. The remains of the subfossil lemurs are relatively recent, with all or most species dating within the last 2,000 years. Humans first arrived on Madagascar around that time and hunting likely played a role in the rapid decline of the lemurs and the other megafauna that once existed on the large island. Additional factors are thought to have contributed to their ultimate disappearance. Oral traditions and recent reports of sightings by Malagasy villagers have been interpreted by some as suggesting either lingering populations or very recent extinctions.