Most of the information about the biology of the mammals is from captive animals (2). They are largely solitary (2) and though once thought to be nocturnal (6), are now known to be active during the day (2). They feed largely on leaves, grasses, fruits and fungi, some of which are known to be poisonous. It has been suggested that this is why okapis eat charcoal from burned forest trees, as is evidenced from their dung (2). Carbon, in the form of charcoal, is an excellent antidote for toxin ingestion and recent observations in Zanzibar found red colobus monkeys eating charcoal from native cooking fires and kilns (7). It is also known that many other animals find sources of kaolin, a type of clay, to offset the effects of poisonous leaves and fruit in their diet.
Male and female okapi live in home ranges, but they are not territorial and these ranges overlap (3). From observations on captive animals, it appears that male okapis mark their ranges with urine, by crossing their front legs, urinating on them, and then walking through their range. They will also urinate directly onto plants. Both males and females rub their necks against tree trunks (3).
Mothers will not stray very far after giving birth, so the young okapi will remain close by until at least a few days old, in what is known as a ‘follower phase’ (3). It then becomes a ‘nester’ for a number of months, in which it lies in vegetation. During this intensive nesting phase, the calf is extremely efficient in the use of energy, primarily only nursing or sleeping. Towards the end of the intensive nesting phase, the calf can maintain its temperature properly, and so activates its rumens (the first chamber of its stomach), and defecates for the first time (3). This is thought to be a defence against predators (2). Okapi mothers use infrasonic communication to communicate with their calves. This is sound that is below the range of human hearing – also used by elephants (3).
The young are weaned at six months old although they may continue to take milk for some time afterwards. The males begin developing their horns at about one year and reach their adult size at the age of three. They are believed to reach sexual maturity around two years old (2). Captive individuals have been known to live for up to 33 years (3).