Goldenrumped sengi

Rhynchocyon chrysopygus

SUBFAMILY

Rhynchocyoninae

TAXONOMY

Rhynchocyon chrysopygus Günther, 1881, Mombasa, Kenya. OTHER COMMON NAMES

French: Rat à trompe à croupe dorée; German: GoldrückenRüsselhündchen; Spanish: Musaraña elefante de trompa dorada.

PHYSICAL CHARACTERISTICS

Rhynchocyon chrysopygus, the golden-rumped sengi, and the two other species within the genus, R. cirnei, the checkered sengi, and R. petersi, the black-and-rufous sengi, are the largest species in the family, and about equal in size. The head and body length of an adult golden-rumped sengi runs 9-12.5 in (235-315 mm), the tail adding another 7-10 in (190-263 mm). Adult weight reaches 14.5-15.5 oz (408-550 g).

The fur is fine, yet stiff in texture, and glossy. The ears are hairless and the tail is less furred than the body. The signature characteristic is a large, bright yellow rump patch. Feet, ears, and legs are black, likewise the tail, exept its lower third, which is white with a black tip. The upper body is deep red-brown and black, the undersides paler. There is a scarcely visible vestige of a checkered pattern on the body similar to that of R. cirnei, more obvious in the young.

Both sexes carry a patch of thickened skin, called a dermal shield, under the yellow rump patch, the shield being thicker in the males. The dermal shield may protect individuals when being bitten on that vulnerable spot by same-species rivals. Complementing the dermal shields are the sexually dimorphic canines, 0.26 in (6.6 mm) long in males, 0.18 in (4.6 mm) in females, and probably seeing service during attacks on rivals.

The snout is reinforced within by a row of 30 rings of cartilage similar to those in a human larynx.

Golden-rumped sengis, like the other species in this genus, have only four toes on front and hind feet, missing the pollex ("thumb") and hallux ("big toe").

DISTRIBUTION

R. chrysopygus is found with certainty only in the Arabuko-Sokoke Forest Reserve on the coast near Mombasa, Kenya.

HABITAT

The Arabuko-Sokoke Forest is a 155 mi2 (400 km2) block of moist and dry coastal tropical forest, the largest surviving fragment of an indigenous forest type that once extended along the east coast of Africa from northern Mozambique to southern Somalia. The forest reserve encompasses 109 acres (44 ha) of the Gedi Historical Monument, while a 2.3 mi2 (6 km2) bloc has been set aside as Arabuko-Sokoke National Park. The forest is under consideration as a World Heritage Site. An estimated 20,000 individuals of R. chrysopygus inhabit the entire forest.

BEHAVIOR

Golden-rumped sengis are diurnally active. Monogamous pairs hold territories sex-specifically, one pair per average territory of 4.2 (1.7 ha), the neighboring territories contiguous, or abutting on one another. Individuals exude a pungent odor from a gland behind the anus, with which the animals mark territory. Both sexes scent-mark territory.

Individuals sleep in shelters made up of small pits lined and covered with leaves. The animals build new shelters every few days, digging out a hollow in the soil, upholstering it with litter leaves and roofing it with more litter leaves into a blanket 3 ft (0.9 m) across. A finished shelter is almost unnoticeable. The monogamous pair builds shelters in the early morning, when leaf litter is moist from dew and less likely to make rustling sounds as the sengis move leaves into place. There may be 10 such shelters in a territory. Individuals of a monogamous pair stay in separate shelters. An individual sleeps in a crouching position, head tucked under forequarters, ready to instantly awake at the sounds of a predator trodding on the edge of the leaf blanket, dashing up through the blanket of leaves and away.

The garishly bright, golden rump may seem a liability in such a vulnerable creature, but it does have a defensive function: its brilliance and motion are likely to catch the attention of a possible predator and tempt it to close in, too early and from too far. The predator, on the hunt, spotting the bright rump patch from a distance, reacts and moves, thus producing slight sounds that the sengi's alert ears can pick up as early warning to facilitate its escape. On sensing the predator in this way, a golden-rumped sengi will slap its tail loudly against the leaf litter, communicating to the approaching predator that the sengi is aware of its presence, is ready to flee, and is too far away to be worth the predator's efforts. If the predator decides otherwise and the sengi chooses to flee, its noisy boundings over the leaf litter warns its mate and young that a predator is in their territory. A golden-rumped sengi in full flight is a memorable sight. The gait has been compared to the stotting, or running in a series of high leaps, of gazelles.

FEEDING ECOLOGY AND DIET

The golden-rumped sengi is the only sengi species that eats exclusively animal food, mostly invertebrates of many sorts, including earthworms, millipedes, insects, and spiders, using its long, flexible snout to poke through leaf litter in search of edibles.

Golden-rumped sengis share a commensal relationship with the red-capped robin-chat (Cossypha natalensis). A red-capped robin-chat will follow a foraging golden-rumped sengi or pair through the forest, feeding on scraps of invertebrates left behind by the sengi.

REPRODUCTIVE BIOLOGY

Golden-rumped sengi sexes mate for life, yet take opportunities to mate with lone individuals. The species breeds throughout the year. Females give birth to a single young after a gestation period of 42 days. The youngster remains in the nest for two weeks, then emerges as a fully weaned individual. It follows the mother while she forages, but is able to fend for itself after five days, although it stays in the parents' territory until establishing its own, anywhere from five to 10 weeks after weaning. Having secured a territory with a mate, an individual can live up to five years.

CONSERVATION STATUS

Rhynchocyon chrysopygus is listed as Endangered in the 2002 IUCN Red List of Threatened Species. That status is due to its limited range and restriction to the forest floor (it cannot climb and does not burrow), the latter condition rendering it vulnerable to wild predators and domestic or feral dogs. People living in areas adjacent to the forest hunt and trap sengis for food, while clearing forested land along its edges.

A support group, "Friends of the Arabuko-Sokoke Forest," made up of Kenyan and foreign individuals and institutions, works actively to protect the forest. The group publicizes, encourages ecotourism, and involves local people in conservation and in using forest products in sustainable ways.

SIGNIFICANCE TO HUMANS

Golden-rumped sengis are hunted for food by locals. From the viewpoint of conservation, they are symbols of a unique and vanishing ecosystem and of the wisdom of protecting it. ♦

PHYSICAL CHARACTERISTICS

The checkered sengi is similar to the golden-rumped sengi in size specifics (adult head and body length 9-12.5 in (235-315 mm), tail adding another 7-10 in (190-263 mm). Adult weight 14.5-15.5 oz (408-550 g). The animal can justly be proud of its unique pelt design: several dark stripes, on each side, running the length of the body, broken into squarish spots of alternate chestnut and off-white, or whitish and dark brown. The main coat color is yellowish to dark brown. In some populations, the distal portion of the tail is white.

DISTRIBUTION

R. cirnei lives in northern and eastern Democratic Republic of the Congo, Uganda, southern Tanzania, northeastern Zambia, Malawi, and northern Mozambique.

HABITAT

Checkered sengis prefer dense, lowland and montane tropical rainforest.

BEHAVIOR

Individuals may live alone, in pairs or in small groups, are active during daytime but are occasionally nocturnal. Pairs or groups vocalize constantly to keep in touch with one another, and tail-rap the ground when alarmed.

FEEDING ECOLOGY AND DIET

Checkered sengis forage for invertebrates on the forest floor in the daytime, alone or in small groups, maintaining group cohesion by continually uttering squeals and squeaks. They make little conical depressions in the soil during their grubbings, offering a sign diagnostic of their presence. The diet is mainly insectivorous, with some emphasis on ants, but they may help themselves to small mammals, birds, bird eggs, mollusks, and other animal foods on occasion. While rooting, the sengis ingest a good deal of dirt, which apparently passes through them with little harm.

REPRODUCTIVE BIOLOGY

Specifics of reproduction are similar to that of the closely related golden-rumped sengi. The litter nest is an inconspicuous heap of leaves in a shallow ground depression. The female bears a single, precocial young.

CONSERVATION STATUS

The 2002 IUCN Red List of Threatened Species lists R. cirnei as Vulnerable. The main problem facing the species is deforestation.

SIGNIFICANCE TO HUMANS None known. ♦

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