Lemur
Lemurs are wet-nosed primates of the superfamily Lemuroidea, divided into eight families and consisting of 15 genera and around 100 extant species. They are endemic to the island of Madagascar. Most existing lemurs are small, with a pointed snout, large eyes, and a long tail. They usually live in trees and are active at night.
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.
Living lemurs range in weight from the mouse lemur to the indri. Since the arrival of humans on the island around 2,000 years ago, over a dozen species of "giant lemurs" larger than living lemur species have become extinct, including the gorilla-sized Archaeoindris. Lemurs share many common basal primate traits, such as divergent digits on their hands and feet, and nails instead of claws. However, their brain-to-body size ratio is smaller than that of anthropoid primates. As with all strepsirrhine primates, they have a "wet nose".
Lemurs are generally the most social of the strepsirrhine primates, living in groups known as troops. They 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 in 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. 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.
Many lemur species remain endangered due to habitat loss and hunting. Although local traditions, such as Fady, generally help protect lemurs and their forests, illegal logging, economic privation and political instability conspire to thwart conservation efforts. Because of these threats and their declining numbers, the International Union for Conservation of Nature considers lemurs to be the world's most endangered mammals, noting that as of 2013 up to 90% of all lemur species confront the threat of extinction in the wild within the next 20 to 25 years. Ring-tailed lemurs are an iconic flagship species. Collectively, lemurs exemplify the biodiverse fauna of Madagascar and have facilitated the emergence of eco-tourism. In addition, conservation organizations increasingly seek to implement community-based approaches to save lemur species and promote sustainability.
Etymology
, the founder of modern binomial nomenclature, gave lemurs their name as early as 1758. With his declaration of the genus Lemur in the 10th edition of Systema Naturae, he included three species: Lemur tardigradus, Lemur catta, and Lemur volans. Although the term lemur was first intended for slender lorises, it was soon limited to the endemic Malagasy primates, which have been known as collectively "lemurs" ever since.The name lemur is derived from the Latin term lemures, which refers to specters or ghosts that were exorcised during the Lemuria festival of ancient Rome. Linnaeus was familiar with the works of Virgil and Ovid, both of whom mentioned lemures. Seeing an analogy that fit with his naming scheme, he adapted the term "lemur" for these nocturnal primates.
It was noted in 2012 that many sources had commonly and falsely assumed that Linnaeus was referring to the ghost-like appearance, reflective eyes, and ghostly cries of Madagascar's lemurs when he selected the name. Up until then, it had also been speculated that Linnaeus may also have known that some Malagasy people believed that lemurs were the souls of their ancestors. However, both claims were discredited since according to Linnaeus' own explanation, the term lemur was selected because of the nocturnal activity and slow movements of the red slender loris:
Evolutionary history
Lemurs are primates belonging to the suborder Strepsirrhini. Like other strepsirrhine primates, such as lorises, pottos, and galagos, they share ancestral traits with early primates. In this regard, lemurs are popularly confused with ancestral primates; however, lemurs did not give rise to monkeys and apes. Instead, they evolved independently in isolation on Madagascar. All modern strepsirrhines including lemurs are traditionally thought to have evolved from early primates known as adapiforms during the Eocene or Paleocene. Adapiforms, however, lack a specialized arrangement of teeth, known as a toothcomb, which nearly all living strepsirrhines possess. A more recent hypothesis is that lemurs descended from lorisoids primates. This is supported by comparative studies of the cytochrome b gene and the presence of the strepsirrhine toothcomb in both groups. Instead of being the direct ancestors of lemurs, the adapiforms may have given rise to both the lemurs and lorisoids, a split that would be supported by molecular phylogenetic studies. The later split between lemurs and lorises is thought to have occurred approximately 62 to 65 mya according to molecular studies, although other genetic tests and the fossil record in Africa suggest more conservative estimates of 50 to 55 mya for this divergence. However, the oldest lemur fossils on Madagascar are actually subfossils dating to the Late Pleistocene.Once part of the supercontinent Gondwana, the island of Madagascar has been isolated since it broke away from eastern Africa, Antarctica, and India. Since ancestral lemurs are thought to have originated in Africa around 62 to 65 mya, they must have crossed the Mozambique Channel, a deep channel between Africa and Madagascar with a minimum width of about 560 km. In 1915, paleontologist William Diller Matthew noted that the mammalian biodiversity on Madagascar can only be accounted for by random rafting events, where very small populations rafted from nearby Africa on tangled mats of vegetation, which get flushed out to sea from major rivers. This form of biological dispersal can occur randomly over millions of years. In the 1940s, American paleontologist George Gaylord Simpson coined the term "sweepstakes hypothesis" for such random events. Rafting has since been the most accepted explanation for the lemur colonization of Madagascar, but until recently, this trip was thought to be very unlikely because strong ocean currents flow away from the island. In, a report demonstrated that around 60 mya both Madagascar and Africa were 1,650 km south of their present-day positions, placing them in a different ocean gyre, producing currents that ran counter to what they are today. The ocean currents were shown to be even stronger than today, which would have pushed a raft along faster, shortening the trip to 30 days or less—short enough for a small mammal to survive easily. As the continental plates drifted northward, the currents gradually changed, and by 20 mya the window for oceanic dispersal had closed, effectively isolating the lemurs and the rest of the terrestrial Malagasy fauna from mainland Africa. Isolated on Madagascar with only a limited number of mammalian competitors, the lemurs did not have to compete with other evolving arboreal mammalian groups, such as squirrels. They were also spared from having to compete with monkeys, which evolved later. The intelligence, aggression, and deceptiveness of monkeys gave them an advantage over other primates in exploiting the environment.
Distribution and diversity
Lemurs have adapted to fill many open ecological niches since making their way to Madagascar. Their diversity in both behavior and morphology rivals that of the monkeys and apes found elsewhere in the world. Ranging in size from the 30 g Madame Berthe's mouse lemur, the world's smallest primate, to the recently extinct 160–200 kg Archaeoindris fontoynonti, lemurs evolved diverse forms of locomotion, varying levels of social complexity, and unique adaptations to the local climate.Lemurs lack any shared traits that make them stand out from all other primates. Different types of lemurs have evolved unique combinations of unusual traits to cope with Madagascar's harsh, seasonal climate. These traits can include seasonal fat storage, hypometabolism, small group sizes, low encephalization, cathemerality, and strict breeding seasons. Extreme resource limitations and seasonal breeding are also thought to have given rise to three other relatively common lemur traits: female social dominance, sexual monomorphism, and male–male competition for mates involving low levels of agonism, such as sperm competition.
Before the arrival of humans roughly 1500 to 2000 years ago, lemurs were found all across the island. However, early settlers quickly converted the forests to rice paddies and grassland through slash-and-burn agriculture, restricting lemurs to approximately 10% of the island's area, ~60,000 km2. Today, the diversity and complexity of lemur communities increases with floral diversity and precipitation and is highest in the rainforests of the east coast. Despite their adaptations for weathering extreme adversity, habitat destruction and hunting have resulted in lemur populations declining sharply, and their diversity has diminished, with the recent extinction of at least 17 species in eight genera, known collectively as the subfossil lemurs. Most of the approximately 100 species and subspecies of lemur are either threatened or endangered. Unless trends change, extinctions are likely to continue.
Until recently, giant lemurs existed on Madagascar. Now represented only by recent or subfossil remains, they were modern forms that were once part of the rich lemur diversity that has evolved in isolation. Some of their adaptations were unlike those seen in their living relatives. All 17 extinct lemurs were larger than the extant forms, some weighing as much as 200 kg, and are thought to have been active during the day. Not only were they unlike the living lemurs in both size and appearance, they also filled ecological niches that either no longer exist or are now left unoccupied. Large parts of Madagascar, which are now devoid of forests and lemurs, once hosted diverse primate communities that included more than 20 lemur species covering the full range of lemur sizes.