Piliocolobus tephrosceles (Elliot, 1907)

Russell A. Mittermeier, Anthony B. Rylands & Don E. Wilson, 2013, Cercopithecidae, Handbook of the Mammals of the World – Volume 3 Primates, Barcelona: Lynx Edicions, pp. 550-755 : 711

102.

Ashy Red Colobus

Piliocolobus tephrosceles

French: Colobe d'Ouganda / German: Uganda-Stummelaffe / Spanish: Colobo rojo de Tanzania

Other common names: Ugandan Red Colobus

Taxonomy. Colobus tephrosceles Elliot, 1907 ,

Uganda, Toro, Ruahara River, east side of Mount Rwenzori, 1200 m.

Modern taxonomic arrangements of the colobus monkeys either divide the red colobus and the Olive Colobus into two genera, Piliocolobus and Procolobus , respec-: tively, or consider them to belong to one genus, Procolobus , with two subgenera ( Procolobus for the Olive Colobus and Piliocolobus for the red colobus). We follow here C. P. Grovesin his publications of 2001 and 2007 in using two genera. P. tephrosceles was considered to be the eastern Rift Valley subspecies of P. oustaleti by J. Kingdon. There is some geographic variation in this species, although further study is needed to determine if they merit subspecific rank. Monotypic.

Distribution. E border of the W Rift Valley from c.1° N to 8° S in isolated forests in SW Uganda (Kibale), and W Tanzania (Biharamulo, Gombe, Mahale Mts, and Lake Rukwa); possibly in E DR Congo, Rwanda, and Burundi, butits presence has not yet been confirmed.

Descriptive notes. Head-body 45.5-67 cm (males) and 49-58 cm (females), tail 65— 72 cm (males) and 62-68 cm (females); weight 8-11.4 kg (males); no weight data available for females, but they are considerably smaller than males. The Ashy Red Colobus has long, dense fur and a relatively short tail. It is extremely sexually dimorphic. Males are considerably heavier than females, with a more massive head, larger canines, and longer cheek whiskers. A small, light-colored “panache” (a prominent tuft of hair) is present. It is glossy-black above (including tail) and light gray to white below. Forearms and legs are a dull light gray, occasionally with varying amounts of tan or brown on arms, and often redder tones on haunches and upper thighs. Crown is rusty-red with a marked, dark reddish-brown forehead crest bordered by a black stripe on the temples. Face is slaty (except for a trace of pale pinkish tones on eyelids) and outlined with gray whiskers. There is a prominenttuft at the base of each ear. Callosities are slaty or pink. Adult females have a large, prominent clitoris. Its mtDNA affinities are with other East Central African red colobus species, particularly Lang’s Red Colobus ( P. langi ) and eastern QOustalet’s Red Colobus (PF. oustaleti ). There is some geographic variation in color, and it may be that subspecies could be recognized. Populations in the Mahale Mountains (western Tanzania, bordering Lake Tanganyika), for example, tend to be jet-black with restricted red areas on hindquarters, tail becomes black distally, and underside is white. In forests around Lake Rukwa, the southernmost part of its range, populations are more blackish-gray, underside is light gray, sideburns are red, and cheek whiskers are very long. Teeth are relatively small, and the skull is strongly sexually dimorphic in size and is instantly recognized by a curious furrow or crease running between the orbits across the base of the nasal bones.

Habitat. Lowland and montane primary rainforest. In the Kibale Forest of Uganda, the Ashy Red Colobus is most abundant in moist, old growth, evergreen forest, with emergent trees reaching 50 m in height. It can persist in lightly logged forest if important food trees remain.

Food and Feeding. [.eaves make up the vast majority of the diet of the Ashy Red Colobus , although the proportion of young leaves to mature leaves varies between sites and seasons. Flowers and fruit make up a small component of the diet.

Breeding. The female Ashy Red Colobus displays a small pink sexual swelling during the periovulatory period. Breeding does not appear to be seasonal, and the interbirth interval is 25-5 months. Neonates have black silky fur on their back and sides and a gray ventral surface; muzzle, ears, palms, and soles are pink. Subadult males have a relatively small, knob-like perineal organ.

Activity patterns. The Ashy Red Colobus is diurnal and arboreal. At Gombe, Tanzania, T. Clutton-Brock found that it spent 54% of the day resting, 25% feeding, 9% engaging in social activities, 8% moving, and 4% in various other activities. T. Struhsaker, studying the Ashy Red Colobus in Kibale, Uganda, found somewhat different activity patterns: 45% feeding, 38% resting, 9% moving, and 8% engaging in social activities.

Movements, Home range and Social organization. Mean daily movement is 649 m in a 65ha home range. Group sizes are 9-80 individuals, with multiple adult males and females. Females are likely to transfer from their natal groups more often than males.

Status and Conservation. CITES Appendix II. Classified as Endangered on The IUCN Red Last (as Procolobus rufomitratus tephrosceles ). The main threat to the Ashy Red Colobus is habitat loss through selective logging of mature forest for timber, conversion to agricultural land, production of charcoal, and forest fires. To some degree, hunting for meat and skins remains a threat. The Ashy Red Colobus numbers at least 20,000 individuals, with the largest and most viable population in Kibale Forest in Uganda where the population is estimated at 17,000 or more. About 60% of the Kibale Forest National Park has suitable habitat for red colobus, and published density estimates in this habitat are 93-313 ind/km®. Although Kibale would appear to have a healthy and viable population, long-term studies in two areas of the Park indicate statistically significant declines in numbers of Ashy Red Colobus . In the Ngogo study area, census data spanning nearly 24 years indicated a 43% decline in groups, mainly due to predation by Chimpanzees (Pan troglodytes). The Ashy Red Colobus in Gombe Stream National Park also seem to have declined in numbers due to predation by Chimpanzees. Red colobus group sizes have declined by nearly 50% over a 25year period and 16-40% of them are killed each year by Chimpanzees. This is particularly troubling given the very small size (¢.80 km?) and isolation of the Gombe Stream National Park. Besides the Gombe Stream and Kibale Forest national parks, the Ashy Red Colobusis found in Birigi Game Reserve and Mahale Mountains National Park in Tanzania. The population in Kibale Forest National Park may be the only viable one, although recent survey work by T. Davenport and colleagues has shown that at least 1354 Ashy Red Colobus survive on the Ufipa Plateau, with 1217 individuals in Mbizi and 137 individuals in Mbuzi. Long-term monitoring of the Ngogo situation is required, as well as a comprehensive, long-term monitoring program for the colobus in Kibale.

Bibliography. Chapman & Chapman (1999), Clutton-Brock (1974a, 1975a, 1975b), Davenport et al. (2007), Groves (2001, 2007b), Grubb et al. (2003), Isbell (1983), Kingdon (1997), Lee et al. (1988), Nishida (1972), Rodgers et al. (1984), Stanford et al. (1994), Struhsaker (1974, 1975, 1981a, 1981b, 2005, 2010), Ting & Teelen (2011).

Figures

Distribution. E border of the W Rift Valley from c.1° N to 8° S in isolated forests in SW Uganda (Kibale), and W Tanzania (Biharamulo, Gombe, Mahale Mts, and Lake Rukwa); possibly in E DR Congo, Rwanda, and Burundi, butits presence has not yet been confirmed.