Sclater’s Guenon

Name and Classification

Reginald Innes Pocock named this monkey in 1904.^[3] He described a young male from the London Zoo. It arrived in July 1902 and died that August. Pocock named it for Dr. P. L. Sclater. Sclater had asked that guenons dying at the Zoo be skinned.

It belongs to the cephus group of guenons.^[4] Its group includes the red-bellied monkey and the red-eared guenon. The moustached guenon belongs to the group too. So does the lesser spotted-nosed monkey. No subspecies are recognized.

Some authors once treated it as a red-eared guenon subspecies.^[5] Its type locality is given as Benin City. Pocock gave the locality only as "W. Africa: Benin". That record may be doubtful. In 1982, every known wild specimen came from east of the Niger. Benin City lies in the former Bendel State, west of the river.

Physical Description

A band of gold-flecked black and yellow hair crowns its forehead. A black band runs from each eye to the ear. It then circles the back of the crown.

Its cheeks carry tufts of lemon-yellow hair. Its ears end in prominent tufts of white hair. The skin of its muzzle and nose tip is pale pink. Some show a reddish edge on the nose. Pocock's type had a large white patch of hair on its nose.

Its throat is white. Unlike the red-bellied monkey, it has no full white ruff.

The back, flanks and outer limbs are speckled gray and olive-brown. That agouti coat places it among the gray monkeys. Its olive-brown tones also make it one of the brown monkeys. Its underside and forearms are grayish.

Its tail is red underneath near the base. It turns white in the middle, then darkens toward the tip. This pattern varies a lot between animals. Near the Cross River, some show red tints on nose and ears.

Size and Weight

The handbook gives these ranges. It does not give sample sizes.

Male head-body length is 45 to 55 cm (18 to 22 in). Female head-body length is 40 to 45 cm (16 to 18 in). The male tail runs 60 to 75 cm (24 to 30 in). The female tail runs 45 to 60 cm (18 to 24 in).

Males weigh 3 to 4.5 kg (6.6 to 9.9 lb). Females weigh 2.5 to 3.5 kg (5.5 to 7.7 lb). It ranks among the smallest daytime primates in its range.

Similar Species Compared

The red-bellied monkey is its neighbor to the west.^[6] It has a full white throat ruff. Its belly is rusty red or gray. Its nose patch may be white, black or dark brown. East of the Orashi River, the two meet in a narrow zone.^[7] There they overlap and hybridize. The IUCN lists the red-bellied monkey as Endangered.

The red-eared guenon lives farther east, beyond the Cross River.^[8] It has a rusty-red tail and red ear fringes. Its nose spot is reddish. Pocock judged Sclater's guenon nearer to it than to the moustached guenon. The IUCN lists it as Vulnerable.^[9]

Range and Distribution

Sclater's guenon is endemic to Nigeria.^[10] It lives in the south, between the lower Niger and Cross rivers. Its range covers about 28,500 km² (11,000 sq mi). The region is crowded with people and produces oil.

Its range starts in the eastern Niger Delta, in Bayelsa State. It reaches north into Enugu and Ebonyi States. All known sites lie below 130 m (430 ft).

A 2004 regional survey confirmed it at 27 sites unknown before. The team used forest surveys and hunter interviews. By 2013, the handbook counted more than 30 known sites. Even so, most of its populations are small and isolated.

Habitat Needs

Its original home was moist tropical lowland forest. Most of that forest is gone. Today it lives in remnant secondary forest. It also uses riverine and freshwater swamp forest. These forests make it one of the rainforest monkeys of West Africa.

It also survives in farmbush and small village groves. In some villages, scattered trees are all that remain.

A 2011 occupancy study looked at where it lives.^[11] Occupancy peaked where farmland and secondary forest made up 20 to 40%. Human disturbance did not change occupancy.

The 2004 regional survey met it more often in heavily hunted forests. Those authors suggest hunters had removed larger competing monkeys.

Diet and Feeding

No one has studied its diet in detail. The handbook expects mainly fruit, plus leaves and animal prey. The Red List suggests insects and young leaves too. That fruit-heavy diet places it among the frugivorous monkeys. Its mixed diet also makes it one of the omnivorous monkeys.

In sacred villages, it eats crops such as oil palm nuts. It also steals food from houses. In 2005 and 2006 interviews, most residents called crop raiding a drawback.^[12] The share was 92% in Lagwa and 94% in Akpugoeze.

Behavior and Groups

It is active by day. It uses every level of the forest canopy. Where it is hunted, it keeps to thick, low growth.

Short-term observations found groups of 3 to 30 animals. Each group probably has one adult male, plus females and young. Its home range has never been studied. Nothing is known about its breeding.

A 2006 survey near Edumanom also recorded the mona monkey. The greater spot-nosed monkey was recorded there too.

Sacred Village Groves

In a few Igbo and Ibibio villages, people treat it as sacred. Most residents still will not kill these monkeys, despite crop damage.^[13]

Surveys from 2004 to 2006 estimated 124 monkeys in 15 Lagwa groups. Akpugoeze had an estimated 193 monkeys in 20 groups.

Later counts rose. Lagwa's estimate rose from 124 to 206 in 4.5 years.^[14] Akpugoeze's estimate rose from 193 to 249 in four years. A revised count method may explain part of the rise.

A May 2016 census estimated 339 monkeys in Akpugoeze's core area.^[15] Groups there averaged about 14 animals, ranging from 5 to 32. Residents consider the monkeys the property of two local deities. Taboos forbid harming or eating them.

A third sacred population lives at Ikot Uso Akpan, Akwa Ibom State. A 2011 report estimated 178 monkeys there. All three sacred populations must adapt to urbanizing land.

Population and Status

No total population estimate exists. The IUCN assessed it as Endangered in January 2019. It estimates a decline of more than 50% over about 27 years. That span equals three generations of nine years.

Encounter rates in one regional survey were low. Surveyors made 0.18 detections per km walked. In Edumanom Forest Reserve, it was the most common daytime primate seen. One study estimated 3.1 groups per km² there.

Earlier listings varied. It was Endangered in 2000 and Vulnerable in 2008. In 1994, John Oates wrote it may be Africa's most at-risk primate.^[16]

Seven captive Sclater's guenons were tested for Ebola antibodies.^[17] One tested positive, and one was unclear. The positive animal had been confiscated from poachers. No confirmatory test could be run.

Major Threats

Its range has one of Africa's densest human populations. Most forest there has become farmland. Logging and oil production add to the damage. Nigeria lost 98.7% of its primary forest from 1990 to 2015.

Fragmentation is severe. Isolated groups lose contact and genetic diversity.

Hunting for bushmeat is widespread. Hunters prefer larger monkeys, which spares it somewhat. Some hunters skip it because it is small and hard to kill.

In sacred villages, groves are cleared for houses and farms. Informants also report deaths by electrocution.

Conservation Efforts

It is listed on CITES Appendix II. It is in Class B of the African Convention.

Nigeria's 1985 endangered species law covers all monkeys.^[18] Most, including this one, sit in its Second Schedule. That schedule bans hunting or trade without a license.

It does not occur in any officially gazetted wildlife conservation area. Researchers urge moving it to the First Schedule. They also urge protecting three forest reserves. These are Edumanom, Upper Orashi and Stubbs Creek.

School programs and workshops have run in Lagwa and Akpugoeze. Forest restoration has begun at Ikot Uso Akpan. The Red List suggests exploring small-scale ecotourism in these villages.

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