Rhynchocyon chrysopygus mandelai, Agwanda, Bernard R., Rosero, Francesco, Lawson, Lucinda P., Sernesi, Cristiano & Amin, Rajan, 2021

Agwanda, Bernard R., Rosero, Francesco, Lawson, Lucinda P., Sernesi, Cristiano & Amin, Rajan, 2021, A new subspecies of giant sengi (Macroscelidea: Rhynchocyon) from coastal Kenya, Zootaxa 4948 (2), pp. 245-260 : 252-255

Rhynchocyon chrysopygus mandelai , new subspecies

Holotype. NMK 169427 , adult male prepared as study skin, skull, postcranial carcass preserved in 70% ethanol after fixing in 10% formalin, and tissue samples in 98% ethanol ( Figure 2a ). Collected on 22 nd September 2009 by B. R. A. and S. Andanje in the Mangai patch of Boni forest , Lamu County, coastal Kenya ( Figure 5b ). The 12S, vWF, CytB, D-Loop, ND2, and ENAM sequences of the holotype are archived in GenBank with accession numbers: MW 250883 , MW 250886 , MW 250888 , MW 250898 , MW 250900 , MW 250902 , respectively.

Paratypes. One paratype ( NMK 180813 ) consists of a skin recovered in 2010 by B. R. Agwanda and S. Andanje in Boni forest (1.675°S, 41.282°E), 29 m above sea level (a.s.l.) north of Mararani village . The animal was originally captured in a net but was stolen by bushmeat hunters who returned only the skin. A second paratype, preserved as skin ( NMK 180814 ), was captured by hunters in Dodori NR (1.745°S, 41.284°E) at an elevation of 17 m a.s.l. and the skin was donated to B. R. Agwanda ( Figure S1 ). This location is south of Mararani village ~ 20 km from the Kenya-Somalia border .

Type locality. Mangai patch of Boni forest , Lamu County, northern coastal Kenya. The exact site is a forest patch surrounded by a mix of thickets and woodland (1.751°S, 41.172°E; WGS 84 ) at 10 m a.s.l. This location is ~ 150 m north-east of Mangai village and <20 km south of the Kenya-Somalia border ( Figure 1 ) .

Etymology. Our choice of epithet derives from the severe and persisting insecurity in the taxon range, stemming from decades-long lack of peace in bordering Somaliland. Thus, we wish to honor the late Nelson Mandela as the inspiring beacon for peace and prosperity in Africa and link his name with a unique and precious expression of Kenya’s and Africa’s endemic fauna. We propose the common name “Mandela’s sengi” in English (“sengi ya Mandela” in Kiswahili) for this new form, with “Golden-rumped sengi” being maintained as the common name for R. ch. chrysopygus .

Diagnosis. The weight of the holotype is 610 g, which is within the range for R. ch. chrysopygus (410-690 g; see Table 1 for details including sample sizes). This is below the range of R. udzungwensis (658-750 g) and above that reported for R. cirnei reichardi (320-420 g). The holotype total body length is 549 mm, also within the upper range of R. ch. chrysopygus (464-561 mm), nearing the lower value for R. udzungwensis (550-580 mm), slightly above the range for R. petersi (493-525 mm), R. ci. macrurus (461-509 mm), R. ci. reichardi (439-474 mm), and within the range for R. stuhlmanni (458-556 mm) ( Table 1; Rovero et al. 2008). We note that the holotype appears slightly larger than the two paratypes, for which measurements were not recorded. The upper tooth row of the holotype measures 27.4 mm, which is within the range of R. ch. chrysopygus (23.5-29.8 mm), below that of R. udzungwensis (30.2-32.6 mm), and within the range of R. cirnei and R. petersi (23.8-29.0 mm).

Rhynchocyon ch. mandelai differs from R. ch. chrysopygus in lacking the golden rump, presence of the jet-black lower rump and thighs, the dark dorsal line that posteriorly merges into the jet-black rump, and the pronounced nuchal crest of hairs. It is similar to R. ch. chrysopygus in the grizzled yellow-brown/tawny face that extends backwards to around the eyes but not reaching the ears, the maroon sides and shoulders, the paler underparts, and the dark pinnae ( Figures 2-3 ).

Rhynchocyon ch. mandelai shows pelage similarities to R. udzungwensis found in the Udzungwa mountains of south-central Tanzania and the dark coastal form of R. ci. macrurus found in southern Tanzania ( Figures 2-3 ). In comparison with R. udzungwensis , R. ch. mandelai has tawny colored face in contrast to the gray face characteristic of R. udzungwensis ; its flanks are uniformly maroon-russet while in R. udzungwensis they are yellow-rufous to orange-rufous with similar, darker maroon-russet only confined to the dorsal line; its underparts are slightly paler than in R. udzungwensis and its body mass is about 100 g less ( Rovero et al. 2008). Rhynchocyon ch. mandelai differs from R. petersi as it lacks the jet-black that in R. petersi extends from the rump to the back and forward almost to the scapular region; it lacks the orange-russet flanks of R. petersi ; the face of R. petersi is bright rufous ( Corbet & Hanks 1968). In comparison with R. ci. macrurus, R. ch. mandelai lacks the near-black pelage that extends from the rump up onto the back and down onto the sides ( Corbet & Hanks 1968), whereas the jet-black fur of the R. ch. mandelai is restricted to the rump and thighs. The differences of R. ch. mandelai with the other forms of R. cirnei are clear: the former lacks the distinct checkers, a series of dark and light spots arranged along several rows on the back, that are unique to R. cirnei ( Corbet & Hanks 1968) , while in R. ch. mandelai only very faint and indistinct darker stripes and checkers are visible, similarly to other Rhynchocyon forms. In addition, the length of the erected nuchal crest appears unique to R. ch. mandelai ( Figure 3 ).

Description. The texture, sparse density and glossiness of the pelage resembles that of other Rhynchocyon species. The tubular nose is dark gray to black and is hairless at the tip but gradually presents very fine, short (2.9 mm on average) vibrissae towards the nares, which is a common feature of giant sengis. As this tubular nose reaches the muzzle, the mystacial vibrissae become thicker and longer (34.2 mm long) and are embedded in swollen bases that form distinctive “moustaches” on either side of the nose at the point where it broadens onto the muzzle and forehead. Three long vibrissae sprout from a single spot on the orange-rufous cheek, immediately below the eye. On the broad, flat forehead individual hairs are yellow-ochre with black bases, which gives a grizzled, tawny “agouti” pattern to the diamond-shaped forehead and extending backwards to around the eyes. The temples are rufous orange and the naked pinnae are dark brown tending towards dark gray. At the peak of the forehead, the hairs abruptly become deep rufous-maroon, and rise to a 72 mm erectile crest. The crest tapers off down the neck where a similarly colored dorsal dark rufous-maroon stripe widens along the back to the anterior back where it merges with the darker maroon and jet-black rump. Behind the eyes, around the ears and to the forelimbs, the fur is yellow-rufous, turning rufous-maroon on the flanks and forming an indistinct border with the darker dorsal fur and with the black fur of the thighs. The belly is pale rufous, with paler tones starting in the vicinity of the forelimbs and becoming yellow on the chest and chin. Along either side of the maroon dorsal stripe there are two slightly darker lines that run parallel on either sides and which are barely visible. Even less obvious, indeed only discernible in strong and angled light, are three pairs of paler spots on each side, which are located dorsal and ventral of the lower darker line ( Figure S2 ). Such vestigial checkering appears similar to that reported for R. ch. chrysopygus , as well as R. petersi and R. udzungwensis . All four limbs are black. Ventral to the base of the tail there is a small naked region. The sparsely haired tail is gray dorsally and paler, almost cream colored ventrally; it measures 293 mm in length and resembles that of R. ch. chrysopygus in having an anterior dark brown section (125 mm) followed by a white, sub-terminal section (95 mm) and ending with a black tip (34 mm).

Distribution and habitat. Records of R. ch. mandelai are from Boni-Dodori forest, east of the lower Tana river ( Figure 1 , Table S2). This is a mosaic of wooded savannah, thickets, and forests representing the largest Kenyan coastal forest area ( Amin et al. 2016). Distribution limits are 1.564S, 41.215E to the north, 1.909S, 41.301E to the south, 1.725S, 41.342E to the east, and 1.681S, 40.861E to the west. The resulting polygon predicts a total distribution of 1980 km 2 ( Figure 5 ).

Identity tests of similarity of ecological niche reject similar environmental conditions in the ranges of the two subspecies (Schoener’s D for R. ch. mandelai vs. R. ch. chrysopygus = 0.0163; Null distribution: mean = 0.7999, 95% CI = 0.7925 -0.8073), which matches the completely non-overlapping areas of predicted distributions ( Figure 5 ).

Within the range of R. ch. mandelai, records are confined to forest patches that include areas with continuous, closed canopy forest cover and with a thick layer of leaf litter on the forest floor, as well as areas with bushland, thickets and forest edges. No records are reported from grassland or open woodland, despite surveys including these habitats. Thus, R. ch. mandelai appears to prefer dry forests with an intact canopy layer reaching a height of 10– 15 m.

Variation. There is little variation in the pelage pattern of the specimens, although the nuchal crest of hairs is of variable length across specimens, measuring 50 mm in the holotype, 38 mm in the paratype NMK 180814, and 29 mm in the paratype NMK 180813. We also examined 843 camera-trap images from the survey by Andanje et al. (2010) and Amin et al. (2016) and found no discernable variation in the pelage pattern.

Figures

FIGURE 1. Distributions of giant sengi (Rhynchocyon) species and subspecies. (A) Map of Africa with a black rectangle indicating the extent for B. (B) Ranges of Rhynchocyon taxa with a black rectangle indicating the extent for C. Distributions are drawn as polygons, encompassing all known localities of each taxon from work by G. Rathbun deposited in www.sengis.org and used with permission. (C) Map of the Kenyan coastal region showing the location of the two subspecies of R. chrysopygus (R. ch. chrysopygus and R. ch. mandelai).

FIGURE 2. (A) Photographs of R. chrysopygus mandelai subsp. nov. holotype prepared as study skin (NMK 169427), and (B-C) two camera-trap images from surveys conducted by Amin et al. (2016) showing lateral-dorsal and frontal views, respectively.

FIGURE 3. Comparison of skins of Rhynchocyon. From top to bottom within each plate: R. chrysopygus chrysopygus (NMK 2122), R. chrysopygus mandelai subsp nov. (NMK 169427, holotype), R. udzungwensis (MTSN 6902), R. petersi (MTSN 6901), R. cirnei reichardi (MTSN 6915) (A: lateral view, B: dorsal view, C: ventral view).

FIGURE 5. Estimated range of R. chrysopygus mandelai subsp. nov. (A) Species distribution model of R. ch. mandelai in the coastal region of Kenya and greater Kenya (inset). Warmer colors represent areas of higher likelihood niche, while cooler colors (blue) represent unlikely occupation. Records of R. ch. chrysopygus and R. ch. mandelai are shown as black dots. (B) A minimum convex polygon was drawn around all recorded sightings of R. ch. mandelai (orange stars). This polygon was extended to include areas which had a high likelihood of occurrence based on ecological niche models created in Maxent (dark green areas). The type locality of R. ch. mandelai is indicated with a larger yellow star.