True lemur

12 species comprise the genus Eulemur, of which seven are members of the fulvus species group.^{[6]: 515–516}

• Family Lemuridae
  • Genus Hapalemur: bamboo lemurs
  • Genus Lemur: the ring-tailed lemur
  • Genus Prolemur: the greater bamboo lemur
  • Genus Varecia: ruffed lemurs
  • Genus Eulemur: true lemurs
    • fulvus group
      • White-headed lemur, E. albifrons
      • Gray-headed lemur, E. cinereiceps
      • Collared brown lemur, E. collaris
      • Common brown lemur, E. fulvus
      • Red-fronted lemur, E. rufifrons
      • Red lemur, E. rufus
      • Sanford's brown lemur, E. sanfordi
    • other true lemurs
      • Crowned lemur, E. coronatus
      • Blue-eyed black lemur, E. flavifrons
      • Black lemur, E. macaco
      • Mongoose lemur, E. mongoz
      • Red-bellied lemur, E. rubriventer

The species that are now considered to be true lemurs were previously members of the genus Lemur, alongside the ring-tailed lemur (Lemur catta).^[5] This was derived from Carl Linnaeus' taxonomy, published in the 1758 10th edition of the Systema Naturae, wherein the red slender loris (Lemur (recte Loris) tardigradus), the ring-tailed lemur, and the Philippine colugo (Lemur (recte Cynocephalus) volans) comprised the genus Lemur. The term "lemur" later came to refer exclusively to Malagasy animals, and the genus Lemur grew to include the modern true lemurs.^[7] Elwyn LaVerne Simons and Yves Rumpler removed every species except for L. catta from Lemur in 1988, instead placing them in a new genus, Eulemur.^[5]

The first author to describe the mongoose lemur was Mathurin Jacques Brisson in 1762, however his binomial name for the species, Prosimia fusca was written adjectivally. As such, taxonomic priority belongs to the subsequent Linnaean name mongoz.^[7] Henry Ogg Forbes assigned the seven members of the fulvus species group as variants of the mongoose lemur in 1894, although this taxonomy resulted from confusion between the mongoose and common brown lemurs.^[8] The Comorian population of mongoose lemur was previously considered to be a separate taxon named albimanus.^[9]

The gray-headed lemur was at first considered to be a variant of the mongoose lemur, with a type locality in Farafangana.^[5] The species' trivial name was coined by Alfred Grandidier and Alphonse Milne-Edwards in 1875 as Lemur (recte Eulemur) cinereiceps. However, their account was not accompanied by a formal description.^[7] Furthermore, their illustrations of their L. cinereiceps were of a female specimen, whereas subsequent specimens were of sexual dichromatic males, obfuscating subsequent descriptions of the species. The gray-headed lemur was obscure in scientific literature until Colin Groves published a description in 1974. Unaware of Groves' description, Rumpler described a male specimen as Lemur albocollaris the following year. The name albocollaris continued to be used for over three decades, until a 2008 survey by Steig E. Johnson et al. found that Grandidier and Milne-Edwards' and Rumpler's descriptions referred to different sexes of the same species, thereby assigning taxonomic priority to E. cinereiceps.^[6]: 546

In his revision of lemur taxonomy, Ernst Schwarz considered the black lemur (Lemur (recte Eulemur) macaco) to be synonymous with the fulvus species group, which was at the time recognized as a single species, Lemur fulvus, with many subspecies.^[7] Schwarz's arrangement, which did not take into account the cranial differences between E. fulvus and E. macaco,^[8] was later found to be incorrect, as the black lemur exists in discrete, sympatric populations alongside members of the fulvus species complex.^[7][8]

Edward Turner Bennett identified a lemur specimen as Lemur (recte Eulemur) rufifrons in the 1833 Proceedings of the Zoological Society of London.^[7] This was considered by many subsequent authors to be a taxonomic synonym of what is now regarded as E. rufus, until morphological and genetic differences between then-recognized populations of E. rufus north and south of the Tsiribihina River were identified by Pastorini et al. in 2003.^[5][10] The taxonomic name rufifrons was resurrected to identify the population north of the Tsiribihina.^[5]

The final extant true lemur taxon to have its subspecies elevated to specific statuses was the black lemur, from which the blue-eyed black lemur (E. flavifrons) was elevated by Mittermeier et al. in 2008.^[5] The name flavifrons had been coined by John Edward Gray in 1867, and was sometimes used to refer to macaco individuals that lacked ear tufts prior to the recognition of the E. flavifrons species.^[7] The term flavifrons initially referred to a female specimen. This resulted in Philip Sclater naming a male specimen Lemur nigerrimus, which he believed to be a separate species from E. flavifrons. Another early theory about the relationship between blue-eyed black lemurs and other true lemurs posited that the male was a melanistic variant of a fulvus group member, such as the white-headed lemur. Schwarz likewise believed that females were variants of the collared brown lemur.^[8]

True lemurs exhibit little variation in morphology between species,^[11]: 65 although species found in the west tend to be smaller and of lighter colorations than those in endemic to the east of the island.^[6]: 495 With the exception of the common brown lemur,^[5] the true lemurs exhibit sexual dichromatism, whereby males and females have different pelage colorations.^[6]: 495 Pelage differences between species are greater among males than in females.^[4]

The white-headed lemur has a head-body length of 39–42 centimeters (15–17 in), a tail length of 50–54 cm (20–21 in), and an average body weight of 1 kilogram (2.2 lb). Males are identifiable by their dark brown dorsal coats and tails, pale gray ventral pelages, and black muzzle with a white beard, crown, and cheeks.^[6]: 534 The ears are almost covered by white fur.^[11]: 67 Males exhibit two different morphs, one with a white forehead and one without.^[5] In lieu of a white framing to the face, females have gray fur on the face and muzzle.^[6]: 534 Female white-headed lemurs closely resemble female Sanford's brown lemurs.^[11]: 67 The white-headed lemur has a somatic number of 2n = 60, with four submetacentric autosomal chromosomes, and 54 acrocentric autosomal and two acrocentric sex chromosomes.^[7]

The gray-headed lemur has a head-body length of 39–40 cm (15–16 in), a tail length of 50–55 cm (20–22 in), and a body weight ranging between 1.9 and 2.0 kg (4.2 and 4.4 lb). Males are endowed with a white or cream-colored bushy beard, while females possess a shorter, red-brown beard that matches the color of the coat. The crown and muzzle of the female is slate gray, whereas the male possesses a dark gray crown with a black muzzle.^[6]: 546 The somatic number of the gray-headed lemur is 2n = 48, with six metacentric chromosomes, ten submetacentric chromosomes, 30 acrocentric autosomal chromosomes, and two acrocentric sex chromosomes.^[7]

The collared brown lemur is 39–40 cm (15–16 in) long, notwithstanding a 50–55 cm (20–22 in) tail, and weighs 2.1 kg (4.6 lb) on average.^[6]: 554 It resembles the gray-headed lemur,^[11]: 67 albeit the face is generally darker and the male beard is a creamy red-brown, rather than white.^[6]: 554 The amount of dark coloring on the head varies between individuals. This resulted in Gray erroneously describing specimens with the darkest head colorations as Lemur melanocephalus in 1863.^[8] The collared brown lemur exhibits genetic polymorphism, whereby three karyotypes are known: 2n = 50, 51, and 52. 2n = 52 consists of six or eight metacentric autosomal chromosomes, four submetacentric autosomal chromosomes, and 40 or 38 acrocentric autosomal chromosomes, alongside two acrocentric sex chromosomes. 2n = 50 also has four submetacentric autosomal chromosomes and two acrocentric sex chromosomes, although it differs from 2n = 52 in that it has ten metacentric and 34 acrocentric autosomal chromosomes. 2n = 50 may have arisen from 2n = 52 as a result of centric fusion. 2n = 51 may be the result of hybridization between 2n = 50 and 52.^[7]

The crowned lemur is among the smallest Eulemur species,^[11]: 68 being 34–36 cm (13–14 in) long with a 41–49 cm (16–19 in) tail, and weighing between 1.1 and 1.3 kg (2.4 and 2.9 lb). Males have gray-brown backs with chestnut-brown flanks and limbs. Ventrally, they are creamy-gray. Among males, an orange V-shaped "crown" mark connects the ears to the eyebrows, and descends either side of the cheeks. Females are generally grayer, and have less prominent "crown" patterns that do not descend to the cheeks.^[6]: 572 The somatic number of E. coronatus is 2n = 46. It exhibits six metacentric chromosomes, 12 submetacentric chromosomes, 26 acrocentric autosomal chromosomes, and two acrocentric sex chromosomes.^[7]

The blue-eyed black lemur has a head-body length of 39–45 cm (15–18 in), a tail length of 51–65 cm (20–26 in), and a weight of 1.8–1.9 kg (4.0–4.2 lb). Males are wholly dark, though the hairs are sometimes tinged with brown shades, and a ridge crest of hair is present atop the forehead. Females have red-tan or red-gray backs, with a creamy-white or gray ventrum, and a slate-gray muzzle.^[6]: 566 Females can be differentiated from the closely related black lemur females by being generally lighter-colored. The blue-eyed black lemur is the only primate species that consistently exhibits blue eyes.^[11]: 68

Some common brown lemurs (Eulemur fulvus) have white patches above their eyes; others do not.

The common brown lemur has a head-body length of 40–18 cm (15.7–7.1 in), a tail length of 45–55 cm (18–22 in), and weighs about 1 kilogram (2.2 lb).^[6]: 518 Though females are slightly lighter than males,^[11]: 66 the species exhibits generally similar pelage colorations between males and females, and is the only Eulemur species to do so.^[5] Females appear to have slightly sharper faces than males, due to differences in fur arrangement.^[7] Its coat is gray-brown on the back. Above a light-colored beard, the head is dark.^[5] The tail darkens towards the tip.^[11]: 66 Individuals from the north of the species' range possess pale patches above the eyes, while those found elsewhere do not.^[6]: 518 The common brown lemur has a somatic number of 2n = 60, featuring four submetacentric chromosomes and 54 acrocentric autosomal chromosomes, as well as two acrocentric sex chromosomes.^[7]

The black lemur is medium-sized, being 39–45 cm (15–18 in) long with a 51–65 cm (20–26 in) tail, and weighing about 1.9 kg (4.2 lb). Like the blue-eyed black lemur, males of this species are darkly colored, ranging from chocolate-brown to black. Among females, the dorsal coat can be golden-brown or chestnut-brown, with a white or gray abdomen, beard, and ear tufts. The face is black.^[6]: 560 Both sexes have prominent ear tufts that descend to the neck, framing the face.^[11]: 67 The somatic number of the black lemur is 2n = 44, wherein 12 autosomal chromosomes are metacentric, eight are submetacentric, and 22 autosomal chromosomes and the sex chromosomes are acrocentric.^[7]

The mongoose lemur is one of the smaller true lemurs, as it is 30–35 cm (12–14 in) long with a 45–48 cm (18–19 in) tail, and can weigh between 1.1 and 1.3 kg (2.4 and 2.9 lb). Males have a gray-brown back with a dark patch on the rump and rusty-brown neck and shoulders. They are distinguished by a rufous beard. Females are lighter than males, and have a cream-colored abdomen. Females also have darker faces with white beards that connect the ears to the throat and forelimbs.^[6]: 584 Two pairs of mammae are present, although only one is functional.^[7] Males sometimes have bald spots on the tops of their heads from rubbing during scent-marking behaviors.^[6]: 584 The fur is dense, especially so among higher-altitude populations such as those on the island of Anjouan.^[7] Mongoose lemurs of the Comoros sometimes exhibit pelage variations that differentiate them from Malagasy mongoose lemurs, although these differences are not consistent among all individuals in the Comorian population.^[5] The mongoose lemur has a somatic number of 2n = 60, wherein four autosomal chromosomes are submetacentric, and 54 autosomal chromosomes and the sex chromosomes are acrocentric.^[7]

The red-bellied lemur is a medium-sized true lemur, with a head-body length of 35–40 cm (14–16 in), a tail length of 43–53 cm (17–21 in), and a weight of 1.9–2.1 kg (4.2–4.6 lb). Both sexes possess a dorsal coat of long, chestnut-brown fur. Males have a reddish ventral coat, whereas females' are creamy-white. The face exhibits white teardrop-shaped marks on the skin below the eyes, which are larger in males and smaller in females. The red-bellied lemur does not exhibit a beard or ear tufts such as those seen in other true lemurs. Instead, the males have patches of dense fur around the ears and cheeks that make the face appear robust.^[6]: 578 Like the mongoose lemur, males sometimes exhibit bald spots on their heads as a result of repeated rubbing while scent-marking.^[11]: 69 The red-bellied lemur has a somatic number of 2n = 50. It exhibits two metacentric chromosomes, 12 submetacentric chromosomes, and 34 acrocentric autosomal chromosomes. The sex chromosomes are acrocentric.^[7]

The red-fronted lemur is one of the larger species of Eulemur, being 40–48 cm (16–19 in) long with a 45–55 cm (18–22 in) tail, and weighing about 2.1 kg (4.6 lb) on average. Males have iron-gray backs with paler gray ventral coats, whereas females are olive-gray on the back with pale red undersides. Infants of both sexes are born with pelages resembling those of adult males, with females adopting their sex-specific colorations at 7–17 weeks of age.^[6]: 526 Despite its resemblance to the red lemur, the red-fronted lemur is more closely related to the white-headed lemur, common brown lemur, and Sanford's brown lemur.^[5]

The red lemur has a head-body length of 40–48 cm (16–19 in), a tail length of 45–55 cm (18–22 in), and an average body weight of about 1.6 kg (3.5 lb). Males are generally olive-gray with a brick-red crown and a golden-red cheek beard. A vertical black stripe connects the crown to the nose. Females are reddish with orange undersides and golden-red beards.^[6]: 524 Both sexes have white markings above the eyes, which are themselves below red markings exhibited by males.^[11]: 66 The red lemur has a somatic number of 2n = 60, with four submetacentric autosomal chromosomes, 54 acrocentric autosomal chromosomes, and two acrocentric sex chromosomes.^[7]

Sanford's brown lemur is medium-sized, with a head-body length of 38–40 cm (15–16 in), a tail length of 50–55 cm (20–22 in), and a body weight ranging between 1.8 and 1.9 kg (4.0 and 4.2 lb). The backs of males are brown, connecting to darkly-colored tails. Ventrally, a male is pale brownish-gray. Males are notable for their ear tufts, which can be off-white to rusty in coloration, as is the case with the large male beard beneath the face.^[6]: 540 Together, the beard and ear tufts appear as a mane wreathing the male Sanford brown lemur's face,^[5] which is itself is black. Females are gray-brown on the back and on the tail, while they are pale gray on the front. They have light patches above the eyes, and lack the beard and mane of the males.^[6]: 540 Female Sanford's brown lemurs closely resemble the females of E. albifrons.^[5] The somatic number of Sanford's brown lemur is 2n = 60, featuring four submetacentric chromosomes, 54 acrocentric autosomal chromosomes, and two acrocentric sex chromosomes.^[7]

True lemurs can be pair-bonded or exist in multimale-multifemale groups of up to 20 members.^[6]: 496

True lemurs are typically frugivorous, maintaining diets that prioritize the consumption of fruit food items. The quantity of fruit consumed relative to other food items varies between seasons. True lemurs that live in dry forests typically consume a smaller amount of food species as opposed to the dietary diversity exhibited by rainforest species.^[6]: 495 In captivity, meat is more readily consumed if it has been cooked.^[8]

Female true lemurs are seasonal breeders, being receptive to copulation only during a yearly mating season that lasts from two to six weeks. The gestation period is about 120 days in length.^[6]: 496 Infants are born with blue irises,^[8] and are carried on their mothers' abdomens. Weaning occurs at six or seven months of age.^[6]: 496 Females engage in alloparental care, as they will exchange infants between each other for nursing.^[8]

The seven members of the fulvus group have an allopatric distribution, whereas they may live in sympatry with non-fulvus members of Eulemur.^[4]

Eulemur distribution

Range of the fulvus group: red = E. fulvus, green = E. collaris,

purple = E. rufus, orange = E. cinereiceps,

blue = E. rufifrons, yellow = E. albifrons,

brown = E. sanfordi

Range of the other Eulemur: red = E. rubriventer, green = E. mongoz,

purple = E. coronatus, orange = E. flavifrons,

blue = E. macaco

Populations of red-fronted lemurs and collared brown lemurs have been introduced to Berenty Reserve in the extreme south of the island, and have hybridized there.^[5]

True lemurs are especially vulnerable to predation by the fossa (Cryptoprocta ferox) and birds of prey.^[6]: 496