Black-and-white colobus

Colobuses live in territorial groups that vary in both size (3-15 individuals) and structure.[2][18][19] It was originally believed that the structure of these groups consisted of one male and about 8 female members.[20] However, more recent observations have shown variation in structure and the number of males within groups, with one species forming multi-male, multifemale groups in a multilevel society, and in some populations supergroups form exceeding 500 individuals.[18][19] There appears to be a dominant male, whilst there is no clear dominance among female members.[2] Relationships among females are considered to be resident-egalitarian, as there is low competition and aggression between them within their own groups. Juveniles are treated as a lower-rank (in regards to authority) than subadults and likewise when comparing subadults to adults.[3] Colobuses do not display any type of seasonal breeding patterns.[21]

As suggested by their name, adult colobi have black fur with white features. White fur surrounds their facial region and a "U" shape of long white fur runs along the sides of their body. Newborn colobi are completely white with a pink face. Cases of allomothering are documented, which means members of the troop other than the infant's biological mother care for it. Possible explanations to this are, increasing inclusive fitness or maternal practice which will benefit future offspring.[22]

Angolan black-and-white colobus with infant.

Many members participate in a greeting ritual when they are reunited with familiar individuals, an act of reaffirming.[2] The greeting behaviour is generally carried out by the approaching monkey and often is followed with grooming. They participate in three greeting behaviours of physical contact. This includes mounting, head mounting (grasps the shoulders) and embracing.[2] It seems as though these behaviours do not have any relationship with mating or courting.[2]

Adult Eastern black-and-white colobus with a juvenile

Black-and-white colobus have complex sleeping patterns. They sleep in trees near a food source, which may serve to save energy.[4] Groups seem to regularly switch up sleeping locations (suggested due to reducing risk of parasites and placement prediction) and generally do not sleep near other groups. They also tend to sleep more tightly together on nights with great visibility.[4] They sleep in mid- to upper sections of tall trees which allows for predator watch as well as protection from ground and aerial predators while they are asleep.[4] Although there is no obvious preference for tree type, they have often been observed in Antiaris toxicaria.[4]