Dendrohyrax interfluvialis, Oates & Woodman & Gaubert & Sargis & Wiafe & Lecompte & Dowsett-Lemaire & Dowsett & Gonedelé Bi & Ikemeh & Djagoun & Tomsett & Bearder, 2022

Oates, John F, Woodman, Neal, Gaubert, Philippe, Sargis, Eric J, Wiafe, Edward D, Lecompte, Emilie, Dowsett-Lemaire, Françoise, Dowsett, Robert J, Gonedelé Bi, Sery, Ikemeh, Rachel A, Djagoun, Chabi A M S, Tomsett, Louise & Bearder, Simon K, 2022, A new species of tree hyrax (Procaviidae: Dendrohyrax) from West Africa and the significance of the Niger-Volta interfluvium in mammalian biogeography, Zoological Journal of the Linnean Society 194 (2), pp. 527-552 : 541-544

DENDROHYRAX INTERFLUVIALIS SP. NOV.

BENIN TREE HYRAX

( FIG. 6 )

ZooBank registration LSID: D45FC680-1A5F-4D9D-8A24-19E58ABAE24C.

Holotype: Skin and skull of an adult of unknown sex, NHMUK 46.360 .

Type locality: Ilaro Forest Reserve (6°47′N, 3°04′E), Ogun State, Nigeria .

Distribution: Known only from the region between the Niger and Volta Rivers in West Africa, in moist and dry forest zones; this area encompasses portions of south-eastern Ghana, southern Togo, southern Benin and south-western Nigeria ( Fig. 1 ).

Paratypes: NHMUK 50.337 : Nikrowa , Okomu Forest Reserve, Edo State, Nigeria ; NHMUK 50.338 : Ohosu Forest Reserve , Edo State, Nigeria ; NHMUK 61.461 : Ibadan , Oyo State, Nigeria ; NHMUK 1998.300 : Western Niger River Delta, Delta State, Nigeria ; USNM 377548 : Sapoba Forest Reserve , Edo State, Nigeria ; University of Ghana , Legon, Zoology Museum ZD /L/S3/001: Tafi-Atome , Volta Region, Ghana .

Representative DNA sequences: Sequences of mitochondrial DNA from D. interfluvialis were deposited in GenBank with the following accession numbers: MW 147258 and MW 147260 – MW 147263 (Cytb, five representatives); MW 147240 , MW 147242 – MW 147244 and MW 147258 ( COX 1, six representatives); MW 592436 – MW 592438 (full mitogenomes, three representatives). Details are given in the Supporting Information ( Tables S2 and S 3 ).

Etymology: The specific name acknowledges the geographical range of D. interfluvialis between two of the largest rivers in West Africa: the Niger and the Volta. The English name ‘ Benin tree hyrax’ (used by Bearder et al., 2015) refers to the occurrence of this species in the south of the Republic of Benin (formerly Dahomey) and in proximity to Benin City in Nigeria. Benin City was once the capital of the Benin Empire, whose influence at its height extended from the Niger to present-day Ghana; these lands are adjacent to the Bight of Benin in the Gulf of Guinea. Dowsett-Lemaire & Dowsett (2019) used the name ‘ Dahomey tree hyrax’ for the population of this species living in the Dahomey Gap.

Diagnosis: Dendrohyrax interfluvialis has a distinctive ‘rattle–bark’ loud call, different in structure from the ‘klaxon’ call of D. dorsalis . The D. arboreus loud call varies regionally and resembles that of D. interfluvialis in exhibiting a series of rattles, but differs by ending in a number of raucous screams ( Milner & Gaylard, 2013). Dendrohyrax validus loud calls sound different and have been divided into three regionally distinct types (variously described as ‘knocks’, ‘hacs’, ‘thwacks’ and ‘wheezes’) ( Roberts et al., 2013).

The pelage of the flanks and outer limb surfaces of D. interfluvialis is brindled dark brown and lighter yellow–brown, in contrast to the predominantly dark brown to blackish dorsal colour seen in populations of D. d. dorsalis , D. d. nigricans and D. d. sylvestris in other parts of West Africa. Individuals of D. d. emini and D. d. latrator from the Congo Basin and of D. d. marmota from the western shore of Lake Victoria are generally much paler in colour than the West African tree hyraxes; they typically have brindled light grey–brown dorsal coats, tinged with yellow on the flanks and rump. However, some D. d. emini individuals are dark brown ( Hatt, 1936). The dorsal pelage of D. arboreus is grey or brown ( Milner & Gaylard, 2013) and that of D. validus varies in colour from cinnamon brown to black; the long hairs around the dorsal gland of D. validus are yellow or cinnamon in colour, compared with white or creamy white in other Dendrohyrax taxa ( Roberts et al., 2013). The considerable variation in coat colour both between and within Dendrohyrax populations has probably contributed to the confused state of current taxonomy.

The skull of D. interfluvialis differs from that of most populations of D. dorsalis in having a short upper diastema (shorter LUD than D. d. dorsalis , D. d. emini, D. d. latrator and D. d. sylvestris) and a mandible with a higher and broader mandibular condyle (higher MCH and broader MCW than D. d. dorsalis , D. d. emini, D. d. latrator and D. d. sylvestris). The skull of D. interfluvialis differs from that of populations of D. dorsalis found to its east in being relatively short, with a shorter, narrower rostrum, narrow nasal choanae, a short palate and a short lower toothrow (shorter average CPL, shorter LTPL and PBPL, narrower GWR and PWC, shorter PPL and shorter LTL than D. d. dorsalis , D. d. emini, D. d. latrator and D. d. nigricans). The skull of D. interfluvialis differs from that of populations to its west in being moderately broad, with a moderately broad interorbital region, broader nasal choanae and a moderately high lambdoidal crest (wider ZB, broader LIB and GIB, broader PWC and higher LCH than D. d. sylvestris). The width across the incisive foramina ( MWIF) in D. interfluvialis is broader than in D. d. latrator, D. d. dorsalis and D. d. sylvestris.

Description: A medium-sized (head and body length 50–55 cm), robust, short-legged mammal, with no external tail. Like other members of the Hyracoidea , the forefeet have four blunt toes (although the fourth digit is vestigial) and the hind feet have three. Most toes have short nails, but those on the first digits of the hind feet are longer and more claw like. The ears are relatively small (25 mm), rounded and black, bearing a few short hairs. The coat is thick and coarse. The dorsal surfaces, including the flanks and outer surfaces of the limbs, are predominantly brindled tawny brown in colour ( Fig. 6A ), an appearance resulting from the light brown tips of otherwise dark grey hairs. The midline of the back has predominantly blackish grey hairs with few light tips, except for a conspicuous middorsal patch of long (70 mm) creamy white erectile hairs associated with an apocrine skin gland. The ventral coat is light buffy brown. There are long black vibrissae on the eyebrows (35–60 mm in length, mean 47 mm) and slightly longer, stouter vibrissae on the snout (35–70 mm, mean 51 mm) posterior to an area of naked black skin surrounding the nostrils. There is also a scattering of white vibrissae beneath the chin, and the dorsal neck has a scattering of long, light guard hairs. The dorsal surfaces of the feet are covered with short dark grey hairs, and the soles of the feet have padded pinkish grey–brown skin. The perineal skin is pink, with scattered grey and white hairs.

Compared with D. dorsalis , D. interfluvialis has a relatively small, narrow skull with a short, narrow rostrum; a short upper toothrow; a short upper diastema; narrow nasal choanae; and a low lambdoidal crest. The mandible has a high, broad mandibular condyle and short lower toothrow. From its neighbour to the east, D. d. nigricans, D. interfluvialis differs in having a shorter, narrower skull with a shorter, narrower rostrum; shorter palate; shorter maxillary and mandibular toothrows; shorter upper diastema; much narrower nasal choanae; and broader width across the incisive foramina. From its neighbour to the west, the eastern population of D. d. sylvestris, D. interfluvialis differs in averaging a slightly longer, broader skull, with a shorter, broader rostrum; broader interorbital region; shorter upper diastema; broader nasal choanae; higher lambdoidal crest; broader width across the incisive foramina; and higher, broader mandibular condyle.

Ecology and natural history: Direct field observations of the feeding behaviour of D. interfluvialis or analyses of its stomach contents have not been made. In the literature, D. dorsalis is described as typically foraging alone on leaves, fruits, bark and twigs ( Shultz & Roberts, 2013), but we have not found reliable data from the field to support this statement.

Bloomer (2013) described all Dendrohyrax species as arboreal and nocturnal. However, our camera trapping in Ghana’s Volta Region shows D. interfluvialis moving in and out of rock crevices on steep hill slopes, both in daylight and at night (see Fig. 6 ); of 22 separate camera sequences of hyraxes moving on the ground near these rocks, nine were recorded during the night and 13 by day. Local people report that the hyraxes sleep among these rocks. In the same area, tree hyrax remains have been observed in snares set for ground-living farm pests, such as cane rats (S.K.B. and J.F.O., personal observations, 2016). Terrestrial locomotion (and possibly feeding) is probably a particularly significant component of the behaviour of D. interfluvialis , at least within the dry forests and wooded savannas of the Dahomey Gap in south-eastern Ghana, southern Togo and southern Benin, where trees are often widely spaced. Although there is little ecological information associated with most museum specimens of D. interfluvialis , the tag attached to NHMUK 50.338, collected by P. F. Mason in 1939 in the Ohosu Forest Reserve (in what was then the north of Benin Province, western Nigeria), notes that the animal was ‘shot on ground in high forest containing some secondary regrowth’.

Behaviour such as terrestrial movement, hiding amongrocksanddiurnalactivitymightbemorecommon among tree hyraxes generally than has been assumed. In the Nouabalé-Ndoki National Park ( Congo) in 1996, F.D.-L. observed a D. d. nigricans walking slowly along a sloping mossy trunk close to the ground in swamp forest during daytime, and in his original description of Hyrax stampflii (= D. d. sylvestris), Jentink (1886: 212) wrote that the specimen collected by Stampfli in Liberia was ‘captured in a cavern of a very high rock’. In montane forest at 3100 m a.s.l. in the Virunga Volcanoes in Rwanda, a radio-tracking study found D. arboreus active throughout the 24 h cycle, with adult females being equally active by day and by night ( Milner & Harris, 1999), and at 4000 m a.s.l. in the Afroalpine zone of the Ruwenzori Mountains in Uganda, D. arboreus is often observed among rocks on the ground in daylight ( Kingdon, 1971; Mason & Oates, 1977). In the mountains of Tanzania, D. validus has been reported to den among large boulders ( Roberts et al., 2013).

Conservation: Probably as a result of its cryptic habits, the fact that it is at least partly nocturnal and arboreal, its apparently solitary foraging activities and the lack of obvious nocturnal ‘eyeshine’ owing to the absence of a tapetum lucidum, D. interfluvialis is not readily located by human hunters and does not appear to be a major target of hunting for meat; the species is not commonly encountered in bushmeat markets. Nor is it hunted as a crop pest, although it is occasionally snared in traps set for rodent pests. Skins and heads of hyraxes, including from the new species, have been observed in fetish markets in southern Benin (‘marchés de dépouilles’; C.A.M.S.D. and P.G., personal observations), indicating that this hyrax is one of a range of species hunted for traditional practices. A greater threat to the survival of D. interfluvialis populations is likely to be the loss of habitat resulting from conversion of forest to cropland (including tree plantations) and from dryseason burning to promote the growth of grassland for consumption by domestic stock. Such habitat loss is exacerbated by the continuing growth of human populations in the range of this species and the spread of settlements and roads. According to an assessment by the FAO (2015), the average annual rate of loss of forest and woodland in the 1990–2015 period was 1.2% in Benin, 3.5% in Nigeria and 5.0% in Togo. The same FAO document reports an average annual increase of 0.3% in forest and woodland in Ghana in the same period, but this is not consistent with the estimate by Dowsett-Lemaire & Dowsett (2014) of a 1–2% annual rate of deforestation in 41 forest reserves in south-west Ghana, based on a comparison of observations from their field surveys in 2008–2010 with assessments made in 1990–1992 by Hawthorne & Abu-Juam (1995). In the absence of numerical evidence of population size or rate of decline for D. interfluvialis , the Red List threat category that probably applies best to this species at this time is ‘Least Concern’, but the general rate of habitat loss within its range suggests that a ‘Near Threatened’ designation might be appropriate, at least in the near future.

Figures

Figure 1. Point localities from which Dendrohyrax call recordings, skulls and tissue samples used in this study were collected, mapped according to current taxonomy (except for Niger–Volta interfluvial population). Triangles indicate calls; circles, skulls; diamonds, DNA; star, type locality; green, Dendrohyrax dorsalis sylvestris; dark blue, Dendrohyrax dorsalis nigricans; turquoise, Dendrohyrax dorsalis dorsalis; pink, Dendrohyrax dorsalis latrator; red, Dendrohyrax dorsalis emini; black, Dendrohyrax dorsalis marmota; purple, D. dorsalis ssp. undet.; orange, Dendrohyrax interfluvialis (Niger–Volta interfluvial).

Figure 6. A, B, camera-trap images of Dendrohyrax interfluvialis in front of rock crevices at Nyagbo Anyigbe, Volta Region, Ghana, in March 2020: A, at 09.12 h; and B, at 23.30 h. C, view of part of Nyagbo Anyigbe; the hill where hyraxes were photographed is on the left, behind the village.