Lesulas ( (Hart, et al., 2012)) inhabit a limited interfluvial range of about 17,000 km2 in the eastern central basin of the Democratic Republic of the Congo. Lesulas occupy lowland rain forests between the Tshuapa and Lomami rivers; the biogeographic barriers of these two rivers may have contributed to the original isolation and speciation of lesulas. Latitudinally, lesulas populate forests between 3° 30′ S and 1° S.
Lesulas dwell in lowland evergreen tropical forests, preferring humid climates and areas with lush abeum trees (Gilbertiodendron dewevrei). Sightings of lesulas occur more frequently in mature forests than in regenerating forests close to human activity; the species has never been observed in seasonally flooded forests or in southern savanna regions. Moving through the forest canopy and on the ground, populations of lesulas travel between 400 and 715 m in elevation. (Hart, et al., 2012)
Slim, medium-sized lesulas exhibit high color contrast in their coat patterning, with blond fur along their upper chest, throat and chin. Black fur covers their lower ventrum and abdominal region, fading into silver-grey tones on the proximal half of their thighs. Amber fur grows on the proximal end of their long, slender tails, gradually darkening to black towards the tip. The fur on their shoulders and long forelimbs is black. Their face, ears and eyelids are naked and range from pink-grey to tan. Large orbits and golden-brown eyes contribute to a focused gaze that the popular media has christened "human-like". Lesulas and their sister species owl-faced guenons (Cercopithecus hamlyni) can be distinguished from all other species of genus Cercopithecus by their vertical nose stripe, facial mane and skull shape. Mature adult males exhibit vibrant blue patches of bare skin on their perineum, buttocks and scrotum. Lesulas and owl-faced guenons display different dental patterns; lesulas possess larger incisors and molars. (Hart, et al., 2012)
Lesulas are sexually dimorphic: females have shorter, lighter bodies and paler gray perineal coloring. Juveniles also exhibit substantially different pelt and perineal patterns, the young lack the distinctive vertical nose stripe and have pale blond coats. By three months of age, young develop an reddish area at the base of their tail. In addition, juvenile males do not display the blue genital pigmentation of adult males. Since the discovery of lesulas in 2012, only a few individual members of the species have been captured, photographed or observed. Hence, indicated ranges of mass and length are tentative and subject to change upon the future study of larger populations. Notably, no mature females of the species have yet been catalogued, making the precise range of body sizes difficult to determine. (Hart, et al., 2012)
At present, the mating practices of lesulas are largely undocumented. Given their many anatomical and behavioral similarities, the reproduction of owl-faced guenons may provide preliminary insights. Sexually dimorphic owl-faced guenons display polygynous mating patterns; multiple females live and reproduce with a single male while rearing their young. No observational data currently suggests the adoption of monogamous mating patterns within the species. Early data on lesulas suggests that, like owl-faced guenons, the brightness of the bare skin on the male's perineum, buttocks and scrotum may serve as an indicator of sexual maturity and readiness to mate. (Fuentes, 1998)
Due to the lack of data, preliminary hypotheses about lesulas' reproduction are based upon the practices of its sister species. Owl-faced guenons have a breeding season that stretches from May to late October and November, fluctuating slightly based on yearly regional rainfall. Like all guenons, lesulas and owl-faced guenons are viviparous, and after sexual fertilization and a gestation period of 5 to 6 months, a female delivers one offspring, or in rare cases, twins. Mature females of most guenon species will bear offspring, on average, once ever two years. Juvenile lesulas and owl-faced guenons appear strikingly different from mature individuals. The juvenile coat is pale and monochromatic, and depending on age, the characteristic nose stripe on the skin of their face may be indistinct or entirely absent. Though little data are available on the maturation process of young lesulas or the age of first mating, one young female observed from about 3 months of age achieved adult body size and fur coloration at about 15 months. (Gevaerts, 1992; Hart, et al., 2012; Tacutu, et al., 2013)
While there are no specific accounts of parenting for lesulas or owl-faced guenons, these species may conceivably display investment patterns common among other guenons. Among members of genus Cercopithecus, females bear well-developed offspring, and then care for their young over a period of approximately six months. (Tacutu, et al., 2013; Tacutu, et al., 2013)
Accurate data on the lifespan of lesulas in the wild or in captivity have not yet been obtained. For owl-faced guenons, their sister species, the oldest individual on record lived 28.6 years in captivity, with the average lifetime in captivity approaching 27 years. (Hakeem, et al., 1996; Tacutu, et al., 2013)
Lesulas are shy and semi-arboreal, traveling and resting on the ground and in the tree canopy. During the limited observations of this species in the wild, 35% of individuals were observed on the forest floor when they were first sighted. Upon contact with humans, individuals frequently fled. They travel either alone, in groups of conspecifics (usually of 5 or fewer members) or in small multi-species assemblages with other primates, such as Wolf's guenons (Cercopithecus mona wolfi), red-tailed guenons (Cercopithecus ascanius katangae) or red colobuses (Procolobus badius tholloni). (Hart, et al., 2012)
The home range of lesulas is, as yet, undocumented.
Lesulas communicate vocally, with vocalization frequency spiking substantially in the period immediately around dawn, from 05:45 to 06:30 in the morning. This “dawn boom chorus” stands in sharp contrast to their relative silence during the rest of the day. In some cases, a substantially smaller increase in vocalization rates has been recorded during the period following sundown. Though the exact function of vocal communication remains unknown, callers are likely male. Among other species of Cercopithecus that produce calls of similar tone and frequency, their vocal boom is produced using a laryngeal air sac, which is much larger in males than in females. Sonically, the booms are of descending frequency, moving to a lower tone over the course of the call and average 0.35 seconds in duration. Though booms may be used for more generalized communication, early studies suggest most concretely that some vocalizations function as warning cries to other conspecifics when danger is near; this pattern is also observed in owl-faced guenons. (Hart, et al., 2012)
Lesulas subsist on a wide range of fruits and vegetation, consuming mostly leaves, fruits and flowers of arrowroot plants (Family Marantaceae). In addition to foraging for fruits and leaves in the forest canopy, lesulas also search for food on the ground, occasionally gathering pieces of food dropped from above by other primates. (Hart, et al., 2012)
In the wild, crowned eagles (Stephanoaetus coronatus) and leopards (Panthera pardus) are documented predators of lesulas. Human hunters also pose a major threat to lesulas, frequently capturing and killing juveniles and adults. (Hart, et al., 2012)
As a frugivore in a tropical forest region, lesulas presumably contribute to the distribution of seeds and the continual regeneration of fruit-producing flora. Additionally, the survival of Near Threatened native predators like crowned eagles and leopards is partially linked to their ability to hunt and feed upon lesulas and other guenons. (Hart, et al., 2012)
Hunters sell lesulas' meat in urban bushmeat markets within the Democratic Republic of Congo. (Hart, et al., 2012)
There are no known adverse effects of lesulas on humans.
The interfluvial TL2 region of the Congo, the sole range of lesulas, does not currently face major threats of destruction from mining, logging or human deforestation. Nevertheless, bushmeat overhunting threatens to trigger a rapid population decline among rare Congolese primates, including lesulas. In the wake of lesulas' official designation as a new species in 2012, wide scale media coverage of the region has encouraged the Congolese government and numerous global wildlife organizations to support the creation of a protected wildlife preserve in the TL2 region. If approved and monitored to prevent poaching, the majority of lesulas ranges will be protected in the Lomami National Park and the Réserve Naturelle de Sankuru. The creation of this park would also contribute to the survival of other endemic species in the Lomami Basin, such as the Lomami River red colobus (Piliocolobus rufomitratus), Lomami River blue monkey (Cercopithecus mitis), and Kasuku River Wolf’s monkey (Cercopithecus wolfi elegans). (Hart, et al., 2012)
Though lesulas have not yet been placed on the IUCN Red List, early assessments by researchers in the field indicate a provisional assessment of Vulnerable. This assessment is related to the reduction of the population size due to uncontrolled hunting for bushmeat. (Hart, et al., 2012)
The extremely recent discovery of lesulas by the broader scientific community means that research is still limited and preliminary. So far, sample groups of individual lesulas have been small, great potential exists for continued research and advancement of knowledge about the species.
Bonnie Antosh (author), Yale University, Eric Sargis (editor), Yale University, Leila Siciliano Martina (editor), Animal Diversity Web Staff.
living in sub-Saharan Africa (south of 30 degrees north) and Madagascar.
uses sound to communicate
Referring to an animal that lives in trees; tree-climbing.
having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.
uses smells or other chemicals to communicate
to jointly display, usually with sounds, at the same time as two or more other individuals of the same or different species
animals that use metabolically generated heat to regulate body temperature independently of ambient temperature. Endothermy is a synapomorphy of the Mammalia, although it may have arisen in a (now extinct) synapsid ancestor; the fossil record does not distinguish these possibilities. Convergent in birds.
parental care is carried out by females
an animal that mainly eats leaves.
A substance that provides both nutrients and energy to a living thing.
an animal that mainly eats fruit
An animal that eats mainly plants or parts of plants.
offspring are produced in more than one group (litters, clutches, etc.) and across multiple seasons (or other periods hospitable to reproduction). Iteroparous animals must, by definition, survive over multiple seasons (or periodic condition changes).
having the capacity to move from one place to another.
the area in which the animal is naturally found, the region in which it is endemic.
having more than one female as a mate at one time
rainforests, both temperate and tropical, are dominated by trees often forming a closed canopy with little light reaching the ground. Epiphytes and climbing plants are also abundant. Precipitation is typically not limiting, but may be somewhat seasonal.
breeding is confined to a particular season
remains in the same area
reproduction that includes combining the genetic contribution of two individuals, a male and a female
associates with others of its species; forms social groups.
uses touch to communicate
the region of the earth that surrounds the equator, from 23.5 degrees north to 23.5 degrees south.
uses sight to communicate
reproduction in which fertilization and development take place within the female body and the developing embryo derives nourishment from the female.
young are relatively well-developed when born
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