The Udzungwa Red Colobus are found exclusively in the Udzungwa Mountains in central Tanzania, east Africa. This monkey is just one of many species endemic to the isolated mountain range, which is covered by a rich tropical rainforest, rivers, and bordering grasslands. Leaves are the most important part of their diet, anything from 70% and 90% of their diet. Their remaining diet is filled out by fruits and flowers. Although many of the plants they eat are highly toxic, containing chemicals such as cyanide, these monkeys have physically adapted to this by developing larger salivary glands and a larger, sacculated stomach. Mothers have also been observed teaching their offspring to eat soil, which helps neutralize the toxins. Their most distinctive feature is the red cap on their heads. The rest of the monkey's body is often white on the ventral side and black on the dorsal side. Their faces are covered by mostly black skin and patches of pink scattered on the muzzle. They lack true thumbs. There is only a small nub where their thumb would be. The name colobus comes from the Greek word meaning "cut short" or "maimed," in reference to their lack of a thumb. They make up for this with their four hook-like fingers. This hand structure actually makes it easier for them to quickly leap from branch to branch. Their long tails are non-prehensile and are used primarily to maintain balance when walking across branches. They are the most arboreal of all African primates, only leaving the comfort of the trees when it is absolutely necessary. Like most primates, they are diurnal. They average about 61 cm tall and weighs about 11 kg. Their tail lengths generally match the individual's height. Males are slightly larger than females. Their lifespan is unknown, although their closest relatives have lifespans ranging between 20 and 30 years old. They live in groups of 20 to 40 individuals. Some groups number as high as 81 while other monkeys wander alone. The monkey troop wakes up around sunrise and forages during the early morning. They rest for most of the day and spend much of their down time grooming each other and building social bonds. They forage again in the evening before retiring for the night. They often sleep in the same trees where they were feeding that day, preferring to stay in the tallest trees they can find. The males tend to stay in their natal group for life and develop strong social bonds with one another. They will only usually leave to form a group of their own. Females in the main group often form smaller associations and will move from group to group several times in their lives. They are often suspicious of newcomers. Before joining a new group, a lone monkey may spend several months following and spying on the target group to see if they will accept him. They are fiercely territorial and they often engage in violent battles with neighboring troops. Most of this fighting is left to the males, who also fight within their own troop to rise up the dominance hierarchy. When a predator is nearby, the males will gather together to defend the group while the females, infants, and juveniles escape to safety. They make several vocalizations, but researchers have not yet deciphered their meanings. When these colobuses see a human, adults and juveniles make a "chist" call. Other calls include barks, yelps, squeals, shrieks, and quavers. They mate year-round although more frequently between March and June. Males compete with each other for mating opportunities, but no male holds exclusive mating rights. When a female enters estrus, her anogenital region swells up. After mating, the female has a pregnancy that lasts about six months. Because females move between groups several times in their life, most females in a group are unrelated to each other. Scientists speculate that this is why red colobus mothers do not generally practice allomothering, where all females work together to raise their offspring. Instead, mothers are highly protective of their young from all males and females in the group. On average, females give birth to a new offspring every three years. Females reach sexual maturity at two years of age. At that point, they may go off on their own to find a new group, or they may stay close to their mother and aunts and leave only when they do. Males reach sexual maturity some time between 3 and 4 years old. They are sympatric with several species of primates and have often been seen forming short-term groups with other species. They have formed friendly relationships with yellow baboons, Sanje mangabeys, and Angola colobuses. Such inter-specific associations provide extra protections against predators. The International Union for Conservation of Nature rates them as Vulnerable (IUCN, 2016), stating that the biggest threat to the species is habitat destruction, which has severely fragmented the population. Habitats are destroyed for the sake of logging, charcoal production, and agriculture. Over 90% of them live in the Udzungwa Mountains National Park, which is well protected; however, the remaining individuals live in forests that are either not protected or their protections are not well-enforced. Conservation groups are looking to expand the park to cover adjacent forests that are poorly protected. Another strategy attempts to tackle forest fragmentation by planting and establishing forest corridors to connect isolated patches of forest. This not only requires the planting of new trees but also prevention of bush fires, which often prevent forests from recovering.