The blue duiker (Philantomba monticola) is the smallest and one of the most abundant and widespread of all duiker species. Like other duikers, this diminutive antelope has a distinctive stocky body, large hindquarters, arched back and short, slender legs, a body shape adapted for easy movement through dense undergrowth. The name “duiker” comes from an Afrikaans word meaning “diver”, these species being named for their habit of diving into cover when disturbed; in the blue duiker this behaviour is often accompanied by a loud, sneezing whistle given by the male. Coat colour is quite variable, depending on location, and ranges from slate grey to dark brown, sometimes with a bluish sheen on the back, which gives the blue duiker its common name. The underparts are whitish, as is the underside of the tail, where slightly crinkled white hairs reflect light so well that on the dark forest floor the constantly flickering tail can resemble a light flashing on and off. Blue duikers have large eyes, fairly small ears and a wide, flexible mouth adapted to feeding on fruit. Sexes are similar in appearance and both possess short, spiky horns, though these are sometimes absent in the female or hidden by a short crest of hair. Females may also be slightly larger than males. All duikers have a good sense of smell and possess large, obvious, slit-like pre-orbital glands in front of the eyes, used in scent-marking.