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Lesula monkey
Scientific classification Edit this classification
Kingdom: Animalia
Phylum: Chordata
Class: Mammalia
Order: Primates
Family: Cercopithecidae
Genus: Cercopithecus
Species:
C. lomamiensis
Binomial name
Cercopithecus lomamiensis
Hart et al., 2012

The lesula (Cercopithecus lomamiensis) is a species of Old World monkey in the guenon genus Cercopithecus, found in the Lomami Basin of the Congo. Though known to locals, it was unknown to the international scientific community until it was discovered in 2007 and confirmed in a 2012 publication. The lesula is the second new species of African monkey to be discovered since 1984.[2] This monkey is described to have human looking eyes and a blue bottom[3][4] "...and adult males have a huge bare patch of skin in the buttocks, testicles and perianal area," said John A. Hart, the researcher who described the monkey. "It's a brilliant blue, really pretty spectacular."[5]

The species was listed among the Top 10 New Species 2013 discovered in 2012 as selected by the International Institute for Species Exploration at Arizona State University out of more than 140 nominated species. Its distinctiveness is its human-like eyes, genital area and booming dawn chorus. The selection was declared on 22 May 2013.[6][7]

Distribution

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Lesula booms

The lesula lives in rainforests in the Democratic Republic of Congo, with the 2007 specimen found in captivity in the village of Opala. Since that sighting, it has also been seen in the wild. Its range is between the Lomami and Tshuapa rivers in the central part of the country.[8]

Status

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The lesula is vulnerable to hunting for bushmeat.[9] Protecting the species could be challenging, as species with such a small range can go from vulnerable to seriously endangered in a few years. The lesula's range is within the Tshuapa–Lomami–Lualaba Conservation Landscape, and the Lomami National Park has been proposed to protect this and other species in the region.

Behavior

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The lesula are generally described by researchers as quiet and shy.[10] They also tend to usually live in small family groups of around five members or less. The Lesula's days consist of leisurely activities such as foraging for fruits and vegetation, grooming, and resting.

References

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Bibliography

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Lesula

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from Grokipedia
The lesula (Cercopithecus lomamiensis) is a medium-sized species of in the , endemic to the lowland rainforests of the (DRC), characterized by its distinctive blond mane, naked pinkish face, and, in males, a striking blue perineal patch. First scientifically described in 2012 after sightings dating back to 2007 in the remote Lomami Basin, the lesula represents one of the largest discoveries in in the 21st century, previously known only to local communities as "lesula." It inhabits mature evergreen terra firma forests between the Lomami and Tshuapa rivers, spanning approximately 17,000 km² at elevations of 400–715 meters, where it prefers humid areas with abundant Gilbertiodendron dewevrei trees. Physically, lesulas are slender and long-limbed, with adult males measuring 47–65 cm in head-body length and weighing 4.0–7.1 kg, while females are slightly smaller at 40–42 cm and 3.5–4.0 kg; their is grizzled gray dorsally with an patch on the back, limbs and , and a diet primarily consisting of fruits, leaves, and flowers from . Behaviorally, they are shy and semi-terrestrial, often traveling in groups averaging about 7 individuals (ranging from 1 to over 30), foraging on the ground more than related guenons (with 98.8% of detections terrestrial), and communicating with low-frequency dawn calls; is likely polygynous, with a 5–6 month period yielding typically one offspring. A 2023 camera-trap study in the Lomami and captured 598 events over 5,960 trap nights, confirming their elusive and cryptic , high terrestriality, diurnal activity, and movements within the Tshuapa-Lomami-Lualaba . Classified as Vulnerable on the as of 2019 due to intense hunting and habitat degradation, the lesula's range overlaps with human settlements, exacerbating threats despite partial protection within the Lomami established in 2012; ongoing emphasizes the need for expanded conservation efforts in this .

Taxonomy and Discovery

Discovery History

The Lesula monkey was first encountered by scientists in June 2007 during surveys in the middle Lomami Basin of central (DRC), when John A. Hart and Terese B. Hart observed a juvenile female held captive in the town of Opala. This initial sighting was followed by the first wild observation in December 2007 near the Obenge River (coordinates: S 1.38461°, E 25.03749°), where field teams documented the monkey in its natural forest habitat. Prior to scientific recognition, local Congolese communities, including hunters in the region, had long known the as "lesula" and reported it as a common in the area, though it had evaded formal Western scientific description due to the remote and poorly surveyed terrain. Between 2007 and 2012, confirmation of the relied heavily on targeted field observations and the deployment of camera traps by the Hart-led teams, which captured photographic evidence of both adults and juveniles in the TL2 landscape—a vast, roadless area encompassing the Lomami Basin. These methods, combined with specimen collection for morphological and genetic analysis, allowed researchers to distinguish the Lesula from similar species and build a robust on its presence and in . The surveys highlighted the monkey's endemicity to this isolated region, underscoring the value of the central forests. In 2012, the Lesula was formally described as a new species, Cercopithecus lomamiensis, in a peer-reviewed article published in PLOS ONE, representing the second discovery of an African monkey species since 1984. This description, based on the accumulated evidence from the 2007–2012 fieldwork, emphasized the species' unique characteristics and the need for further study in its remote habitat.

Classification

The lesula (Cercopithecus lomamiensis) is classified within the Cercopithecus, which comprises the guenons, and belongs to the family Cercopithecidae of monkeys. The Polish vernacular name for the species is "koczkodan sowiolicy". This placement reflects its membership in the diverse tribe , characterized by arboreal and frugivorous adaptations typical of African forest monkeys. The species epithet lomamiensis derives from the Lomami River, which delineates the eastern boundary of its range in the central . Phylogenetic analyses position C. lomamiensis as sister to C. hamlyni (the owl-faced ), with molecular divergence estimated at approximately 1.7 million years ago based on Y-chromosome TSPY gene sequences and 2.8 million years ago using X-chromosome homologs, separating it from other guenons such as C. ascanius (). These genetic data, combined with reciprocal in mitochondrial and nuclear markers, confirm its status as a distinct rather than a or variant of congeners. Confirmation of C. lomamiensis as a unique relies on integrated evidence from morphology and . Cranial features, including larger orbits, an elongated occipital region, and a narrower interorbital breadth compared to C. hamlyni, distinguish it osteologically. Pelage traits, such as a grizzled mane, golden chest, and dorsal patch contrasting with darker limbs, further differentiate it from related like C. hamlyni and C. ascanius. This evidence underscores its endemicity to a restricted area of approximately 17,000 km² within the of Congo's TL2 landscape, isolated by major river barriers that have driven its evolutionary divergence.

Physical Characteristics

External Appearance

The Lesula (Cercopithecus lomamiensis) is a medium-sized characterized by a slender body build with long limbs adapted for an arboreal lifestyle. Adult males measure 47–65 cm in head and body length and weigh 4.0–7.1 kg, while subadult females are smaller, with head and body lengths of 40–42 cm and weights of 3.5–4.0 kg. These measurements are based on a small number of specimens (two adult males and two subadult females). The tail is long and slender, approximately equal in length to the head and body, featuring an amber base that darkens to black toward the tip without a terminal tuft. The fur of the Lesula presents a grizzled appearance overall, with the dorsum covered in black hairs accented by 3–4 bands of buff or coloration, creating a mottled grayish-brown effect. The upper ventrum, including the chest, displays a distinctive golden-yellowish buff hue, while the lower is black; upper arms and shoulders are predominantly black, contrasting with the silvery-gray proximal thighs. A prominent feature is the large framed by a mane of long, grizzled hairs that extend around the face. Facial characteristics include a naked surface ranging from pale pinkish gray to tannish brown on the short, rounded , eyelids, and pinnae, often accented by a variably distinct cream-colored vertical stripe. The eyes are large and golden-brown, set in prominent orbits that contribute to a focused, expressive often described as human-like in popular accounts. This combination of features gives the Lesula a distinctive among guenons, with strong limbs supporting its primarily arboreal habits. Males also exhibit a unique blue perineal coloration, though this is more prominently discussed as a sexually selected trait.

Distinctive Features

The Lesula (Cercopithecus lomamiensis) is distinguished from other guenons by pronounced in coloration, with adult males exhibiting a vibrant and that fades to creamy post-mortem, in stark contrast to the paler gray of females. This bright patch on males serves as a key diagnostic trait, highlighting the species' unique pigmentation patterns among Central African primates. While in body size is present, with males measuring 47–65 cm in head-body length and weighing 4.0–7.1 kg compared to females at 40–42 cm and 3.5–4.0 kg, the differences are most evident in coloration and canine size rather than extreme size disparity seen in some congeners. These measurements are based on a small number of specimens (two males and two subadult females). Facial morphology further sets the Lesula apart, featuring a pale, naked face with a protruding muzzle, large orbits enclosing golden-brown eyes, and a distinctive cream-colored vertical nasal stripe; the presence of white around the eyes contributes to an unusually human-like gaze uncommon in other guenons.

Habitat and Distribution

Geographic Range

The Lesula (Cercopithecus lomamiensis) is endemic to the central (DRC), occupying a restricted distribution in the lowland rainforests of the Lomami Basin. This range is bounded to the east by the Lomami River (approximately 25°E) in and Provinces and to the west by the upper Tshuapa River (approximately 24°E) in Province, encompassing an area of about 17,000 km². Confirmed sightings of the Lesula in the wild began in following its initial discovery, with subsequent observations verifying its presence across the defined basin. Camera trap surveys from 2013 to 2015 in the and adjacent buffer zones recorded 598 independent events over 5,960 trap days, capturing the at multiple sites including Okulu, Losekola, and E15, thus affirming its distribution within the interfluvial landscape. A 2023 analysis of these surveys continues to document the Lesula's presence without evidence of major distributional shifts. The Lomami and Tshuapa Rivers, along with the broader Congo (Lualaba) River system to the south, act as formidable natural barriers limiting the Lesula's expansion and maintaining its isolation from related species, such as the owl-faced monkey (Cercopithecus hamlyni). Prior to , the species' range was undocumented due to the region's inaccessibility and limited scientific exploration, with no substantiated evidence of pre-discovery contraction; however, undocumented local extirpations remain possible given historical anthropogenic pressures in the central basin.

Preferred Habitats

The Lesula (Cercopithecus lomamiensis) primarily inhabits mature lowland evergreen rainforests in the , characterized by high humidity levels and annual rainfall typically between 1500 and 2000 mm, with dense, closed canopies that maintain shaded, moist understories. These forests often feature monodominant stands of Gilbertiodendron dewevrei trees, alongside mixed-species assemblages typical of terra firma environments, which provide the structural complexity essential for the species' persistence. The Lesula avoids seasonally inundated forests, gallery forests adjacent to savannas, and regenerating secondary forests, particularly those near human settlements where disturbance is prevalent. In terms of elevation, the Lesula occupies altitudes ranging from approximately 400 to 715 meters above , within tropical zone of the equatorial region. Microhabitat preferences center on the mid-to-upper canopy layers (3–20 meters and above), where individuals spend significant time foraging and resting, though they exhibit semi-terrestrial tendencies with occasional use of the and for movement along trails. This vertical stratification allows exploitation of diverse resources while minimizing exposure in the humid, dimly lit interior. The equatorial climate of the Lesula's range features a bimodal rainfall pattern, with wet seasons from March to May and September to November, during which the species relies on the increased availability of fruiting trees within the dense canopy to support its ecological needs. In contrast, the drier periods from June to August and December to February see reduced activity, particularly in southern portions of the habitat where ecotones introduce seasonal , underscoring the Lesula's preference for consistently humid, northern blocks.

Behavior and Ecology

Social Organization

Lesula (Cercopithecus lomamiensis) exhibit a social structure typical of many species, forming small to medium-sized multimale-multifemale groups composed of one to two adult males, multiple adult females, and their dependent juveniles and infants. These groups are often led by a dominant adult male who maintains primary mating access in a polygynous system, with females showing while males disperse upon reaching maturity. Field observations indicate an average group size of about 7 individuals, ranging from solitary males or small bachelor groups of up to three males to larger units of up to 32 members, though early encounters suggested smaller units of no more than 5 individuals. Social interactions among lesula are characterized by a quiet and shy demeanor, with daytime communication relying on limited, low-intensity vocalizations such as soft grunts and whines to coordinate group movements or maintain contact. Grooming serves as the primary affiliative behavior, fostering bonds particularly between females and between mothers and , and occurs as part of daily resting periods. Physical displays, such as the vibrant perineal coloration in males, contribute to social signaling within groups. Lesula demonstrate mild territoriality, defending core foraging areas through acoustic displays like pre-dawn "boom" choruses—low-frequency, descending calls produced by multiple group members to advertise presence and boundaries—but they exhibit high tolerance for neighboring groups without frequent boundary disputes. Intergroup encounters are infrequent and typically non-aggressive, involving avoidance rather than confrontation; lesula often form loose multi-species associations with other , such as the wolf's (Cercopithecus wolfi), for , while confirmed hybridization with other guenon species remains unverified despite the genus's propensity for interspecific . Lesula face predation from leopards (Panthera pardus) and crowned eagles (Stephanoaetus coronatus), with field observations documenting attacks on individuals in the wild.

Diet and Foraging

The Lesula maintains an omnivorous diet dominated by ripe fruits, which form the primary component and provide essential energy through high sugar content, supplemented by leaves, flowers, seeds, and such as . Observations confirm consumption of terrestrial herbaceous vegetation, leaf petioles, ripe and unripe fruit parts, flower buds, and meristems from Marantaceae species, aligning with the folivorous-frugivorous patterns seen in related guenons of the l'Hoesti subgroup. Foraging occurs mainly in the understory and on the forest floor, where the Lesula selectively targets available plant resources and manipulates them using its hands for processing and consumption. Individuals often exploit multi-species associations by feeding on items dropped from the canopy by arboreal primates, enhancing foraging efficiency in its semi-terrestrial niche. This specialized low-level minimizes dietary overlap and competition with sympatric arboreal species, allowing the Lesula to occupy a distinct ecological role within its . Group members may coordinate efforts, though detailed roles remain under study.

Locomotion and Activity Patterns

The Lesula (Cercopithecus lomamiensis) exhibits a semi-terrestrial locomotor repertoire, combining arboreal in the canopy with frequent ground travel in the . Observations indicate that it employs brachiation and leaping among branches for navigating upper strata, while on the ground, it primarily uses quadrupedal walking and running. Recent studies confirm a high degree of terrestriality, with 98.8% of recorded events showing all four limbs in contact with the ground, and capture rates 67–500 times higher than those for related arboreal guenons. This pattern aligns with skeletal analyses classifying the lesula as semiterrestrial to terrestrial, spending nearly 50% of its time on the ground—substantially more than most Cercopithecus species, which are predominantly arboreal. The lesula maintains a strictly diurnal , remaining active from approximately 06:00 to 19:00, with rest periods at night spent in trees. Activity peaks occur mid-morning and in the late afternoon, while dawn and dusk show minimal engagement, as evidenced by only 12 crepuscular events across extensive deployments. This schedule differs from the more extended activity of some canopy-dwelling guenons and reflects adaptations to understory foraging pressures. Physical adaptations support this mixed locomotor strategy, including a slender, long-limbed build that facilitates both arboreal suspension and terrestrial progression. Notably, the lesula's postcranial shows a generalized semiterrestrial configuration, with proportions enabling efficient ground travel in dense vegetation—contrasting with the more specialized arboreal forms of congeners like C. cephus. These traits likely evolved to exploit less contested floors, reducing in the canopy.

Reproduction and Life Cycle

Mating and Reproduction

The lesula (Cercopithecus lomamiensis) likely exhibits a , in which a dominant typically monopolizes opportunities with multiple females within the group. This structure is supported by observations of groups consisting of one or occasionally two alongside several females and . Male competition for breeding access is evident from the presence of groups of young , which may challenge resident or form temporary multimale influxes during peak reproductive periods, akin to patterns in other species. Mating displays in male lesulas likely involve visual signaling through the perineum, which is bright blue in adults. Accompanying these displays are vocalizations, including low-frequency "boom" calls that resonate over long distances and are most frequent at dawn, possibly functioning in mate attraction or territorial advertisement during breeding. Breeding in lesulas shows seasonality influenced by rainfall patterns in the Lomami Basin, with mating likely occurring from May to late October or November, aligning with periods of higher resource availability. Births peak from August to October, corresponding to the onset of the second wet season. Females have a gestation period of 5–6 months, after which they typically give birth to a single offspring. Pregnant females often become more reclusive and cryptic to avoid detection during this vulnerable phase.

Development and Lifespan

Following birth, female lesulas provide intensive maternal care to their single , similar to other guenons. Allomothering by non-maternal females may occur, supporting social bonding in multi-female groups. Key growth milestones include around 6 months, when infants begin supplementing milk with solid foods and gradually increase independence. is reached at approximately 3–6 years for females and 4.5–7 years for males, marked by changes in pelage, body size, and secondary such as perineal coloration in males. Juveniles achieve adult body size and full pelage coloration by about 15 months, though reliance on maternal or group care persists for up to two years. In the wild, lesula lifespan is estimated at 15–20 years, influenced by environmental factors and predation risks, while captive individuals of related species have lived up to 25 years. Juvenile mortality is likely high due to predation and , underscoring the precarious stages.

Conservation

Status and Threats

The Lesula (Cercopithecus lomamiensis) is classified as Vulnerable on the of Threatened Species, a status first provisionally assigned in shortly after its formal description. The species' range is fragmented across approximately 20,000 km² (IUCN 2019) in the central Congo Basin, with population size remaining unknown despite survey efforts indicating it is not rare within suitable habitats. The Lesula population is suspected to be decreasing, with ongoing threats exacerbating declines in this remote but increasingly accessible region. Primary risks stem from hunting by local communities, who employ snares and firearms to supply urban markets in nearby towns like and , leading to uncontrolled offtake since the species' discovery heightened awareness and access. further compounds these pressures through selective and expanding agriculture, which degrade the primary lowland forests essential to the Lesula's survival. The ' vulnerability is heightened by its restricted distribution and low resilience to anthropogenic disturbances, including small average group sizes of about 7 individuals (ranging up to 32) that limit social buffering against losses. Slow reproductive dynamics, characterized by seasonal births peaking from to October and typical guenon interbirth intervals of around 2 years, further impede population recovery from and habitat loss. No viable population exists, leaving protection as the sole safeguard against potential rapid escalation to higher threat levels.

Protection Measures

The lesula (Cercopithecus lomamiensis) benefits from as a member of the PRIMATES spp. covered under Appendix II of the , which controls commercial trade to prevent overexploitation that could threaten its survival. In the , protection is provided primarily through the establishment of Lomami National Park in 2016, which encompasses a significant portion of the ' range in the Tshuapa-Lomami-Lualaba (TL2) landscape and prohibits , , and within its boundaries. Additionally, provincial-level safeguards exist in Tshopo Province, where the lesula occurs, though national-level legislation specifically naming the remains pending. A core component of lesula conservation involves efforts within and around Lomami National Park, where regular patrols by eco-guards and TL2 project staff monitor threats and enforce regulations following the park's creation. These patrols, intensified since 2016, collect data on wildlife encounters and human activities while deterring illegal hunting, which targets the lesula for and the pet trade. The park's 8,820 km² area overlaps with key lesula habitats in the central , providing a fortified zone amid broader regional pressures. Ongoing research and monitoring initiatives enhance understanding and protection of lesula populations, including systematic surveys conducted by in collaboration with the TL2 project, which documented over 598 independent lesula events across 5,960 camera days in from 2017 to 2021, with continued efforts into 2023 to assess and distribution. A 2025 study on pressure around the park highlights persistent threats from commercial , emphasizing the need for stronger and . Additionally, a June 2025 genomic study of the lesula revealed high genetic diversity and a divergence from related guenons 3–4 million years ago, providing valuable data for population management and conservation planning. Complementing this, the TL2 Landscape Project implements programs that engage local villages through workshops, brochures, and to raise awareness of lesula conservation, promote sustainable resource use, and reduce reliance on . These efforts foster local in the TL2 region, where communities co-manage buffer zones adjacent to the park. Future conservation strategies for the lesula emphasize expanding protected areas within the TL2 to cover more of its estimated 20,000 km² range, including proposals to strengthen buffer zones and integrate additional interfluvial forests into the system. Initiatives also focus on developing sustainable hunting alternatives for indigenous communities, such as and alternative protein sources, to mitigate human-wildlife conflict while ensuring long-term integrity. Collaborative monitoring and enforcement will remain essential to adapt these measures amid ongoing threats like .

References

  1. https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0044271
  2. https://animaldiversity.org/accounts/Cercopithecus_lomamiensis/
  3. https://pmc.ncbi.nlm.nih.gov/articles/PMC10252051/
  4. https://news.mongabay.com/2024/06/camera-trap-study-brings-the-lesula-congos-cryptic-monkey-into-focus/
  5. https://www.iucnredlist.org/species/92401376/92401776
  6. https://species.wikimedia.org/wiki/Cercopithecus_lomamiensis
  7. https://neprimateconservancy.org/lesula/
  8. https://doi.org/10.1371/journal.pone.0044271
  9. https://doi.org/10.3390/ani13111819
  10. https://pmc.ncbi.nlm.nih.gov/articles/PMC3440422/
  11. https://doi.org/10.1002/ajpa.24025
  12. https://link.springer.com/article/10.1007/BF02389045
  13. https://cites.org/sites/default/files/eng/app/2023/E-Appendices-2023-05-21.pdf
  14. https://news.mongabay.com/2016/07/drc-declares-first-new-national-park-in-20-years/
  15. https://fzs.org/en/programs/democratic-republic-of-the-congo/lomami-national-park/
  16. https://www.bonoboincongo.com/2016/07/13/lomami-national-park-a-new-protected-area-in-d-r-congo/
  17. https://cg.chm-cbd.net/en/protected-areas/lomami-national-park
  18. https://www.fau.edu/newsdesk/articles/lesula-monkey-camera-traps.php
  19. https://www.preprints.org/manuscript/202506.0893/v1
  20. https://www.biorxiv.org/content/10.1101/2025.06.05.657981v1
  21. https://www.esri.com/about/newsroom/arcnews/creating-a-national-park-from-the-bottom-up
  22. https://www.bonoboincongo.com/the-project/
  23. https://news.mongabay.com/2012/09/remarkable-new-monkey-discovered-in-remote-congo-rainforest/
  24. https://onlinelibrary.wiley.com/doi/10.1111/ddi.13677
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