Geographic Distribution and Habitat
The Sclater’s guenon, also known as the Sclater’s monkey and the Nigerian monkey, is endemic to southern Nigeria, from the eastern Niger Delta to the Cross River State. The furthest north its range extends is Anambra-Enugu State and central Ebonyi State. Eleven small populations have been confirmed to exist in the states of Akwa Ibom, Enugu, Imo, Abia, and Cross River State. The localities where this species is found are Utuma, Stubbs creek, Akpugoeze, Osomari, Lagwa, Blue river, and Enyong creek/Ikpa river.
The Sclater’s guenon inhabits floodplain forests (picture a swampy forest with a couple inches of water and some leafy green plants floating on top) at low elevations in Nigeria. Unfortunately, most of the Sclater’s guenon’s natural habitat has become severely degraded, but it persists in remnant secondary forests, marginal forests, and farm-bush in local communities and villages. One such location is the Igbo villages and their sacred tree groves, which sit in the middle of non-native tree plantations and agricultural areas. The Sclater’s guenon is so adaptable that in one area where deforestation has given them no other option, they actually inhabit spaces in the village instead.
It should be noted that the Sclater’s guenon was discovered by researchers in 1904 and was shortly thereafter believed to be extinct until it was sighted again in 1988. More and more populations were recorded between the mid-1990s and 2004, but the Sclater’s guenons is still a very little-studied and endangered primate.
It should be further noted that there has been some speculation in the past that the Sclater’s guenon is actually a hybrid between the red eared guenon (Cercopithecus erythrotis) and the red-bellied monkey (Cercopithecus erythrogaster), but the most recent data still presents the Sclater’s guenon as its own species. Likely the cause for the confusion about its taxonomy is the dearth of information about the Sclater’s guenon coupled with the long-standing belief that it had gone extinct.
Size, Weight, and Lifespan
The Sclater’s guenon is a sexually dimorphic, smaller guenon species. Females weigh approximately 5.5 lbs (2.5 kg) and males weigh approximately 8.8 lbs (4 kg).
There is no recorded lifespan for Sclater’s guenons, but other closely related guenons can live to around 20 years of age.
Occurring or living in the same area; overlapping in distribution.
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Like all guenons, Sclater’s guenons are very colorful monkeys with a striking and complicated facial pattern. Their small faces are fringed by multi-colored tufts of tan and black hair, white tufty ear patches, and a white throat patch. Black bars stretch from their close-set eyes to the back of their head and their nose is a soft, pinkish-white. Overall, their body has a speckled gray pelage with slight variations closer to their hands and feet.
Sclater’s guenons are perhaps best known for their tail coloration: about half of the underside of their long tail is bright rust-red. Their tail also makes up almost one-half of their total body length.
Sclater’s guenons are omnivorous, consuming both plant and animal matter, but they are primarily frugivorous (preferring fruits). Their diet may also include insects, flowers, and leaves, but very little has been recorded about their dietary habits. Researchers do know, however, that in areas where Sclater’s guenons’ habitat has become fragmented, they are forced to raid gardens and farms for food instead.
Behavior and Lifestyle
Sclater’s guenons are arboreal (live in trees), diurnal (active during daytime), and quadrupedal (travel on all fours). They leap about ten percent of the time and use their long tails for balance. They usually sleep in trees at night.
Their home range can be anywhere from 37 to 321 acres (15–130 ha) and they are sympatric with several other species of primates, such as West African pottos (Perodicticus potto), golden pottos (Arctocebus calabarensis), red-capped mangabeys (Cercocebus torquatus), mona monkeys (Cercopithecus mona), and putty-nosed monkeys (Cercopithecus nictitans).
The Sclater’s guenon is an Old World monkey that was first described by Reginald Innes Pocock in 1940 and named after the zoologist and ornithologist Philip Sclater.
Not necessarily a “fun” fact, but the Sclater’s guenon was listed in the IUCN’s 2008–2010 publication of the World’s 25 Most Endangered Primate Species.
Sclater’s guenons have a rather loose group structure, similar to other members of their genus, and therefore can have multi-male groups, multiple family members in a group, or all-female groups. Hopefully, as more research is conducted on the species, we will be able to determine a more well-defined group dynamic for the Sclater’s guenon.
We do know, however, that females seem to make up the core group and will often travel together without a male present. In fact, female independence seems to be very important to the Sclater’s guenon, and the females are the ones that defend their territory from other groups.
In terms of visual communication, the Sclater’s guenon utilizes complex head weaving in conjunction with their striking facial patterns in order to send a message and maintain relationships with other members of a group.
For vocalizations, twenty-two different calls have been described within the described genus Cercopithecus, including calls for group cohesion, warning signals, and other loud calls emitted by males.
As with almost all primates, tactile communication is also very important. For the Sclater’s guenon, grooming behavior indicates a close relationship, as does touching between mothers and their young or between mates. Rival males can be physically aggressive toward one another.
Due to the fact that biologists and researchers did not begin observing the Sclater’s guenon until 1988, and even then could only gather cursory details, there is not much information available about their reproductive habits. However, other members of their genus are polygynous (males mate with multiple females), so it is reasonable to assume the Sclater’s guenon is as well. Males are opportunistic in regard to copulation with females and they engage in head weaving as an important courtship ritual. Females are able to produce their first young at about 5 to 6 years of age.
Generally, the mating season for Sclater’s guenons corresponds with the period of the most food availability, which is July through September, give or take a couple weeks. Gestation lasts for about 6 months and birth occurs anywhere from December until February. Infants weigh 14 oz (400 g) at birth and they cling to their mother’s underbelly for quite some time. They finished nursing by about 9 months of age.
There is little known about the parental investment for Sclater’s guenons, but it is likely that parental care is provided primarily by the mother, as is the case with most other Cercopithecinea. The mother will nurse, carry, and groom her offspring until it is time to wean.
Sclater’s guenons act as seed dispersers due to their diet, which in turn helps the growth of their habitat.
The International Union for Conservation of Nature’s Red List of Threatened Species categorizes the Sclater’s guenon as Endangered with a decreasing population trend (IUCN, 2019). The Sclater’s guenon is estimated to have undergone a population decline of over 50 percent over the past 30 years due to a decline in habitat quality and high levels of exploitation. The rate of population decline is unlikely to accelerate due to continuing habitat loss and degradation.
Sclater’s guenons are able to survive due to their small size, enigmatic behavior, and adaptability. They are generally not favored by local hunters because of their small size and difficulty to hunt relative to other monkeys, but that does not mean Sclater’s guenons are “out of the woods” (well, in a sense, they are, considering most of their forested habitat is severely degraded). The rapidly growing population in Nigeria has caused widespread environmental degradation; during 1976 and 1995, more than half of Nigeria’s lowland forest was lost to agriculture and plantations, a trend that continued at a rate of 3.5 percent annually. This trend of habitat loss is higher than any other African nation. Additionally, the southern region of Nigeria, where Sclater’s guenons live, has one of the highest human populations in the country. So, the combination of a very small remaining habitat and a high human population has resulted in a bleak outlook for the Sclater’s guenon and they remain one of the most endangered primates in Africa.
Sclater’s guenons do not occur in any official wildlife conservation areas and their habitat has been reduced to practically nothing, but there have been recent surveys that have made discoveries of more populations of Sclater’s guenons—though they still occur in small, fragmented patches of forest. There is reason to hope that Sclater’s guenons will survive, however, because they are protected in some villages due to the taboos associated with killing or eating them. In some cases, they are even thought of as protectors of the sacred sites in those villages, which consist of places like Ikot Uso Akpan and other communities in the Itam region (Akwa Ibom State), Lagwa (Imo State), and the Akpugoeze community complex (Enugu State).
There is also reason to hope that Sclater’s guenons’ habitat will soon be protected, because the Cross River State where they occur is recognized as one of the richest forests of the African continent and is therefore being emphasized as a biodiversity hotspot due to the work by the Centre for Education, Research and Conservation of Primates and Nature (CERCOPAN).
Important conservation measures that need to happen include elevating the species to Schedule I of the Nigerian Endangered Species Act, raising awareness about the Sclater’s guenon through publicity and education. It is important to note that this work has already begun in Lagwa and Akpugoeze, where conservation measures include school-based awareness programs, stakeholder workshops, documentation, published folklore and oral histories of primates, and population and forest monitoring. Additional conservation measures that are needed include improving the protection of their forest habitat, including the Edumanom Forest Reserve in Bayelsa State, Upper Orashi Forest Reserve in Rivers State, and the Stubbs Creek Forest Reserve in Akwa Ibom State, analyzing the potential effects of small-scale ecotourism, and enhancing protection in the Niger floodplain, the Ososmari Forest Reserve, the Blue River, and Enyong Creek/Ikpa River.
Written by Rachel Heim, October 2020