the rump is less notable. P. m. aequatorialis is paler and browner than P. m. congicus with a less sharp transition. The stripe is fainter and the back darker in P. m. musculoides. P. m. lugens can be told apart from its darker coloration; the flanks and the dorsal parts are dark grey to brown, the underside grey and a black rump. The diminutive P. m. melanorheus stands apart as well, with black dorsal parts, pinkish grey sides, and long thick fur. The southern subspecies, on the other hand, have reddish tan legs and reddish coats. P. m. hecki is a light fawn to greyish black with light red flanks and a white underbelly; a change in tone can be observed as the rump is a darker reddish fawn. The paler P. m. defriensi is grey in the middle portion of the back, with red to fawn sides, and dark rump and tail. P. m. monticola, light grey to fawn with a reddish rump, is darker than P. m. bicolor, that has reddish-orange flanks. P. m. anchietae is a pale grey or brown on the back with white underparts and a black tail; there is a clear transition from the grey sides and anterior parts to the reddish rump. P. m. simpsoni is distinguished by a facial stripe with white ventral parts; the rump is redder than the flanks. The blue duiker bears a significant resemblance to Maxwell's duiker. However, the latter is nearly twice as large and heavier as the former, with a larger skull. While coloration is more uniform in Maxwell's duiker, the blue duiker shows two different colorations. Another point of difference is the pedal gland (in the hooves), which has a simpler opening in the blue duiker. Walter's duiker is notably lighter in colour; the flanks are brown instead of grey. Ecology and behavior The blue duiker is diurnal (active during the day). Secretive and cautious, it confines itself to the forest fringes. Territorial, individuals of opposite sexes form pairs and occupy territories, nearly large and marked by preorbital gland secretions. The animal rubs the preorbital glands on trees and logs to mark its territory with the fluid produced by the glands. A vocal bovid, bird-like chirps denote curiosity in the animal. It can let out yowls typical of cats if distressed. A female not in oestrus will avoid the male's advances, and may even let