Jackson's Mongoose (Bdeogale jacksoni) is a species of mongoose belonging to the genus Bdeogale. Discovered in 1889 by Frederick John Jackson, Oldfield Thomas in 1894 described it as Galeriscus jacksoni. It is most closely related to the Black-footed Mongoose of the same subgenus Galeriscus and both are sometimes united in a single species.
With a head and body length of more than 50 centimeters and a body weight of two to three kilograms it is a large mongoose. Its long and dense fur is grizzled black and white, the cheeks, the throat and the sides of the neck are very yellowish, the legs are dark brown or black and the bushy tail is white.
Jackson's Mongoose feeds on rodents and insects, especially on army ants, is mainly nocturnal and crepuscular and possibly solitary. Its distributional range in Kenya, Uganda and Tanzania is limited to some arboreous mountain regions. It appears to be rare and in 2008 the IUCN classified it as Near Threatened.
Jackson's Mongoose is a large mongoose with a bushy tail. Its head and body length is 50.8 to 57.1 centimeters, its tail length 28.3 to 32.4 centimeters, its hindfoot length 8.6 to 10.8 centimeters, its ear length 2.3 to 3.5 centimeters and its body weight two to three kilograms. Young but already breeding animals may be markedly smaller than adults. From the Black-footed Mongoose it is distinguishable by its much longer fur, especially on the tail, and yellowish tints on the neck and the throat.
The long and dense dorsal fur is grizzled black and white. The dorsal hairs are 20 millimeters long with black and white rings. The muzzle and the chin are brownish white and the cheeks, the throat and the sides of the neck are very yellowish. The legs are dark brown or black and the tail is white. The ventral side is light gray and the underfur is dense and woolly. The pinnae are round and broad and the muzzle is blunt. The rhinarium is large and the hairless extension of the median groove divides the upper lip. The fore- and hindfeet have only four digits. Hallux and pollex are absent as is common with Bdeogale. The soles are naked and the claws are thick and strong.
The dentition of Jackson's Mongoose is typical for mongooses. There are three incisors, one canine, four premolars and two molars on either side of each jaw. The total number of teeth is 40 and the dental formula is .
Habitat and habits
The habitat of Jackson's Mongoose are montane forests, bamboo zones and lowland forests in mountain vicinity. Its population density is low. It probably hunts frequently in the thick herbaceous growth around swamps.
Jackson's Mongoose is carnivorous, insectivorous and myrmecophagous. In the Aberdare Mountains the volume of food items in 40 scats was over 50 percent rodents including Otomys, Dasymys and Praomys and 40 percent insects, mostly army ants of the genus Anomma, but also weevils, other beetles and caterpillars. Millipedes, snails, lizards and the eggs of snakes were also consumed. About 80 percent of the juveniles' diet were rodents including Otomys, brush-furred mice, true mice and Praomys. They also fed on beetles, lizards, birds and a few ants. Coping with columns of army ants may depend on maturity and learning, which suggests a recent evolutionary adaptation to this diet.
Jackson's Mongoose is mainly nocturnal and crepuscular. In the Udzungwa Mountains 73 percent of 25 photos taken by camera traps during the night were shot between 7 p.m. and midnight. It is possibly solitary but often seen in pairs and occasionally in groups of four. Nothing is known about its reproduction.
The distributional range of Jackson's Mongoose is very limited. It is known from central and southern Kenya, southeastern Uganda and the Udzungwa Mountains 900 kilometers to the south in central Tanzania, where it was first recorded in 2001/02. In the Aberdare Range, the Mount Kenya massif and the Mount Elgon massif it occurs at elevations up to 3300 meters above sea level. In the Udzungwa Mountains it seems highly localized and has only been recorded within Matunda Forest at a maximum of 2.65 kilometers apart. It possibly inhabits other massifs of the Eastern Arc Mountains including the Uluguru Mountains, the Nguru Mountains and the Usambara Mountains.
Jackson's Mongoose is usually considered a species of the genus Bdeogale. It is most closely related to the Black-footed Mongoose (Bdeogale nigripes), from which it is distinguished by skull and skin differences and as whose mountain isolate it is often treated. Both are sometimes united in the species Bdeogale nigripes or in the subgenus Galeriscus, or they are separated from Bdeogale as distinct genus Galeriscus.
Jackson's Mongoose is treated as a separate species by Allen (1939), Rosevear (1974), Corbet and Hill (1980), Honacki et al. (1982), Nowak and Paradiso (1983), Corbet and Hill (1986), Schliemann (1988), Corbet and Hill (1991), Nowak (1991), Wozencraft (1993), Kingdon (1997), Nowak (1999), Pavlinov (2003), Wozencraft (2005), Van Rompaey et al. (2008) and Gilchrist et al. (2009). Kingdon (1977) treats it as a subspecies of the Black-footed Mongoose and Dücker (1972) also considers them conspecific.
Oldfield Thomas in June 1894 described Jackson's Mongoose as type species Galeriscus jacksoni of the new genus Galeriscus. He specified the type locality as Mianzini in the land of the Maasai at an elevation of 8000 feet (2438 meters) above sea level. Reginald Ernest Moreau, George Henry Evans Hopkins and R. W. Hayman in 1945/46 restricted the type locality at Mianzini to a few miles east-southeast of Lake Naivasha, on the southern end of the Kinangop Plateau and to an elevation of 9000 feet (2743 meters).
Frederick John Jackson discovered Jackson's Mongoose in 1889 and in 1894 sent a skin without skull to the British Museum in London. Led astray by the poor and incomplete type specimen, Thomas originally believed it to be related to the grisons. Paul Matschie in 1895 named it Massaimarder (German, "Maasai marten") but was the first to recognize it as a Bdeogale. Reginald Innes Pocock in 1916, too, considered Galeriscus a synonym of Bdeogale. Ned Hollister in 1918 assumed it to be a geographic subspecies of the Black-footed Mongoose.
Population and conservation
Jackson's Mongoose occurs in isolated populations and appears to be rare. There is no reliable data on its population, though. The International Union for Conservation of Nature in 2008 classified it as Near Threatened, almost qualifying as Threatened. This was justified with its assumed decline in population size of 20 to 25 percent within the last 15 years due to habitat destruction. Given its dependence on forest habitat, its main threat is likely to be ongoing forest loss. It was classified as Insufficiently Known in 1988, 1990 and 1994 and as Vulnerable in 1996.
Several populations of Jackson's Mongoose are in protected areas including Aberdare National Park, Mount Kenya National Park, probably Mount Elgon National Park and Udzungwa Mountains National Park. In Tanzania all confirmed localities are within protected areas. It is also probably more widely distributed than currently known. De Luca and Rovero (2006) recommend the full protection of forests adjacent to the Udzungwa Mountains National Park and a survey of other East African groundwater-dependent forests for its presence.