Blue Duiker

About the blue duiker

The blue duiker is the smallest species of duiker, a group of small forest antelope in the family Bovidae. It was first described in 1789 by the Swedish naturalist Carl Peter Thunberg, and today sits in the genus Philantomba alongside Maxwell's duiker and Walter's duiker. At the shoulder it stands only 32 to 41 centimeters (13 to 16 inches), with a head-and-body length of 55 to 90 centimeters (22 to 35 inches) and a weight of 3.5 to 9 kilograms (about 7.7 to 19.8 pounds). Females run slightly larger than males, a pattern typical of the species.

A blue duiker has a flat forehead, large eyes, small white-lined ears, large nostrils, and a broad, mobile mouth. Its dark tail is a little over 10 centimeters (3.9 inches) long and carries a row of white, crinkly hairs on each flank; when the animal flicks its tail while moving through dark understory, those hairs reflect light and produce what looks like a small luminous signal. Short, spiky horns around 5 centimeters (2 inches) long are tucked into tufts of hair on the head. Coloring varies enormously by subspecies and geography, running from blue-grey to brown to nearly black, with many populations showing a visible color break between the back and the rump.

As many as 16 subspecies have been proposed over the years, generally split into a grey-legged northern group and a red-legged southern group based on coloring and range. The blue duiker closely resembles Maxwell's duiker, though Maxwell's duiker is nearly twice its size and weight and has a larger skull; the two also differ in the structure of a scent gland near the hooves. In the wild, blue duikers keep to a broad swath of forest across central, southern, and eastern Africa, from old-growth stands to secondary and gallery forest, and they can turn up in degraded or regenerating forest patches from sea level up to 3,000 meters (9,800 feet) of elevation.

Behavior and diet

Blue duikers are active during the day, which sets them apart from many other small forest antelope, but they are secretive and cautious, sticking close to forest fringes rather than venturing into the open. They are territorial: males and females pair up and share a territory of roughly 0.4 to 0.8 hectares, which they mark with secretions from preorbital glands near the eyes, rubbing the scent onto trees and logs. The species is vocal for a bovid, using bird-like chirps to signal curiosity and cat-like yowls when distressed; a female not ready to mate may let out a whistling call to turn away an interested male.

Diet centers on what falls from the forest canopy: fruit, foliage, flowers, and bark, supplemented with fungi, resin (particularly from Albizia trees), and occasional animal matter such as ants licked off the ground. One study of a dozen stomachs found leaves made up 70 percent of stomach contents by volume, with fruit and seeds at 23 percent, though a separate study found fruit dominating at nearly three-quarters of stomach volume. Blue duikers appear able to subsist on dead foliage better than many other duiker species, and they sometimes follow the movements of birds and monkeys overhead to locate falling food.

The species is monogamous, and mated pairs stay together year-round. Reports on the gestation period vary from as little as four months to as long as seven, and births occur throughout the year, though the birth rate may dip in the dry season. A calf can move on its own within 20 minutes of birth but is mostly kept hidden, nursing three times a day until weaning at 2.5 to 3 months. Males typically disappear for about a month after a calf is born, probably to protect the calf, and females can come back into oestrus just three to five days after giving birth.

Range and habitat

The blue duiker's native range stretches across a wide band of central, southern, and eastern Africa, including Angola, Cameroon, the Central African Republic, the Democratic Republic of Congo, Equatorial Guinea, Gabon, Kenya, Malawi, Mozambique, Nigeria, Rwanda, South Africa, South Sudan, Tanzania, Uganda, Zambia, and Zimbabwe. Within that range it favors forest habitat of several kinds — old-growth, secondary, and gallery forest — because the dense understory offers shelter while the canopy above supplies the fallen fruit and foliage the animal depends on for food.

The species tolerates a fair amount of habitat disturbance and can be found in pockets of degraded or regenerating forest, from sea level up to about 3,000 meters (9,800 feet). It is present in numerous protected areas across its range, including Semuliki National Park in Uganda, Dja Faunal Reserve and Lobéké National Park in Cameroon, Dzanga-Sangha Special Reserve in the Central African Republic, and several national parks in the Republic of the Congo and the Democratic Republic of Congo.

Conservation status

The blue duiker is categorized as Least Concern by the International Union for Conservation of Nature, and its overall population trend is considered reasonably stable. It is listed on Appendix II of the Convention on International Trade in Endangered Species (CITES). Despite the stable population trend, the species faces sustained pressure from bushmeat hunting across its range, a threat that has intensified as human populations have grown in the regions it inhabits.

Blue duiker meat is described as an important source of nutrition within its range, and one researcher who studied the species called it the African ungulate with the greatest combined economic and ecological significance. Even so, the species has shown it can persist despite substantial human interference in its habitat, and it continues to occur in a long list of national parks and reserves across Central Africa, in Uganda, and in numerous protected areas of Southern Africa.