ASHY RED COLOBUS
Geographic Distribution and Habitat
The ashy red colobus (Piliocolobus tephrosceles), also known as the Ugandan red colobus, lives in the jungles of western Uganda and western Tanzania along the eastern border of the Great Rift Valley.
There are only about 20,000 ashy red colobuses alive today. Their population is severely fragmented and only five subpopulations are currently known to exist. The largest and most viable of these–boasting more than 17,000 individuals–lives in Kibale National Park. Here, ashy red colobuses have access to some of the last remaining old-growth evergreen forest left in Uganda, a country where only one-twentieth of its original forest coverage still stands. Much smaller populations of roughly 1,000 individuals or more live in Tanzania near the Biharamulo Game Reserve on the southwestern shores of Lake Victoria, in Gombe National Park, in Mahale Mountain National Park, and in the Mbizi and Mbuzi forests on the Ufipa Plateau. All of these subpopulations are, like the forests they inhabit, in rapid decline.
Subpopulations of ashy red colobuses may also be living in the tropical jungles of the Democratic Republic of Congo, Rwanda, and Burundi. Decades of warfare and political unrest, however, have made it near-impossible for researchers to confirm their presence in any of these countries.
Other populations of ashy red colobus monkeys are known or are suspected to have lived in nearby areas that are now wiped out.
The ashy red colobus is one of 18 red colobus species known to science. It was declared a distinct species as recently as 2001. Its exact taxonomy does remain somewhat controversial, however. Some researchers believe the ashy red colobus might actually be a subspecies of the Tana River red colobus (Piliocolobus rufomitratus). While these taxonomic particulars are important to get right, all red colobus species and subspecies are considered the most threatened primates on the African continent and must be protected.
Male ashy reds are larger than females, weighing roughly 23 pounds (10.5 kg). A female generally weighs about 16 pounds (7.5 kg). Females tend to live longer than males—the average lifespans are 13.7 years for females and 10.5 years for males. However, some females have been known to live as long as 21 years, and some males as long as 15.
Ashy red colobus monkeys are born with black faces that typically lighten to a dark-gray with age. Their most pronounced features are the little caps of red hair on top of their heads that are strikingly distinct from the ashy-gray coats that cover the rest of their body. The hair on their backs and shoulders is dark, fading to a lighter hue around their torsos. Their long dark-brown tails give them the balance they need to live high up in the trees. Their hands and feet are typically dark gray or black in color.
Like other colobus monkeys, the ashy red has notably small thumbs that are convenient for grasping branches and swinging nimbly through the canopy. Their especially large feet give them significant oomph–enough to complete daring leaps between branches of up to 50 feet!
Red colobus monkeys, like the ashy red, are folivorous and eat a large variety of plant and tree species. Their four-chambered stomachs give them the uncanny ability to chow down on leaves that other animals (with less complex stomachs) would find nearly impossible to digest. They usually prefer immature leaves and leaf buds, and will sometimes supplement their diet by eating other parts of plants and occasionally protein-rich arthropods. In addition to giving them a nice pot-belly, their four-chambered stomachs are loaded with helpful bacteria that break down and ferment their high-fiber diet. Digestion within multiple stomach chambers is a slow process, however. As a result, red colobuses are notoriously inactive monkeys and spend up to seven of their ten waking hours lazing around in the canopy digesting their meals. The digestion process creates a build-up of carbon dioxide and methane gas in their system, which frequently makes them burp. This behavior is actually considered a friendly gesture in red colobus culture. Very often, red colobuses will consume charcoal, which acts as a digestive aid.
Degradation and fragmentation of their habitat in Tanzania, in the Rukwa Region, has caused the groups of ashy red colobuses living there to occasionally raid farmers’ bean crops.
Behavior and Lifestyle
Ashy red colobus monkeys are tree-dwelling, diurnal primates. Due to their long, arduous periods of digestion, they are considerably inactive during their waking hours. Following meals, they tend to find nice comfy branches on which to stretch out and relax. Their laidback nature makes them vulnerable to predation. Ashy red colobuses are frequently hunted by local chimpanzee groups who value them for their meat (considered a delicacy by chimp culture). Though agile and quick when they need to be, ashy reds are more likely to fight than they are to take flight. When attacked, they gather close together and the males join forces to ward off the offending chimps and defend their troop.
The ashy red colobus was recognized as a distinct species in 2001.
Ashy red colobuses, as well as other red colobus species, are the most threatened animals in Africa and their health is indicative of the ecosystems that they inhabit.
Those living in Kibale National Forest are considered the last viable population of ashy red colobuses.
Ashy red colobus infants spend more than a quarter of their waking lives engaged in social play–a significantly higher rate than many other primate species.
Despite their seemingly laidback dispositions, ashy red colobuses are particularly social monkeys. Some researchers hypothesize that leaf-eating monkeys have more time to socialize given that they spend significantly less time than fruit-eating monkeys looking for their food—it being all around them after all! So, while the long digestion process gives ashy reds time to recharge, it also gives adults ample time to groom each other and for infants to play together.
In fact, ashy red colobus infants are particularly playful monkeys, engaging in social play for more than a quarter of their day. This happens to be a considerably higher rate of play than any other species of monkeys worldwide. Vervet monkeys, for comparison, are known to spend almost half as much time playing; red-tailed monkeys and blue monkeys (two fruit-eating monkey species that happen to inhabit the same range as ashy reds) only spend up to 2% of their time playing! That doesn’t stop infant ashy red colobuses from trying (and failing) to initiate play with infant red-tailed and blue monkeys they happen to come into contact with.
Infant ashy red colobuses play several games that are instantly recognizable to any human. They regularly engage in fighting and chasing games. These behaviors are notably different than a normal fight or chase, since they are not associated with actual aggression. Participants use special signals to initiate these activities, which communicate that everything that is about to happen is all in good fun. They also take turns, regularly reversing roles. One researcher even observed a group of ashy red infants playing what he could only describe as “follow-the-leader.”
Group size is partly determined by the number of male ashy red colobuses; the more males present in a group the bigger it will be. Male ashy reds remain with their natal group throughout their lives, while females are freer to move at-will between different groups.
The quality of the habitat where a particular group lives also greatly determines the size of ashy red colobus groups. In exceptionally well-protected areas like Kibale and Gombe National Parks, for instance, average group sizes range from 45 to 59 individuals; in less habitable areas like the Mbizi and Mbuzi forests (where populations and forest coverage are already significantly small, and only getting smaller) group sizes average as low as 34 individuals. Researchers have determined that all subpopulations of ashy red colobus are in a state of decline in par with the forests they inhabit.
Large groups of ashy red colobuses frequently break into smaller troops when it comes time to find food and return to each other again once they have had their fill, a phenomenon known as fission-fusion.
Ashy red colobuses will often feed in proximity to other monkey species such as blue monkeys, red-tailed monkeys, gray-cheeked mangabeys, and mantled guerezas. Researchers reason that the ashy red’s eagerness to associate with these other species is likely a strategy for their protection. Since there is safety in numbers, the mingling of species benefits all parties involved. Each species learns to react to the alarm calls of every other species in its vicinity. That way everyone has a better chance of escaping should a common predator appear. Fruit-eating monkeys, like red-tailed monkeys, also tend to be more vigilant about looking out for predators than leaf-eating monkeys, like ashy red colobuses. Therefore, groups of ashy reds that associate with groups of red-tailed monkeys are also likely to benefit from the latter’s keener predator-spotting abilities.
Species of red colobus monkeys are well-known for having a broad range of complex vocalizations. Often, these vocalizations are unique between species and even groups. They are used as mating calls and to warn others of potential threats.
Red colobus monkeys are polygynous, a pattern of mating in which a male has more than one female mates. Unlike other colobus monkeys, red colobus females develop noticeable swellings on their behinds that seem to signal when they are ready to mate. That these swellings often form at times when females are not in estrus suggests that ashy reds benefit from paternity confusion—a behavior observed in other primate species as well, such as chimpanzees. Since males are likely to kill infants they know are not their own progeny, females mate with more than one male in order to make it unclear which of them is the biological father.
Breeding takes place throughout the year. Females initiate intercourse, attracting and courting the males with a series of vocalizations and displays.
Pregnancy lasts between four to six months. At term, a female will only give birth to a single offspring. Unlike some species of colobine monkey, alloparenting is not a common practice among red colobuses. So, once in the world, infants rely on their mothers for just about everything. Remarkably extensive nursing periods give infants plenty of time to learn and master the sets of skills they will need to survive as adults. Come that time, males generally remain with their natal groups while females leave them. Throughout their lifespans, movement between groups is exceptionally more fluid for females than for males.
A female is unlikely to produce another offspring while one remains in her care. Males provide no direct parental support toward raising their progeny. Indirectly, they do protect young from predators and and “provide” for them by locating food and other important resources.
This is speaking of the red colobus species in general. Little is known about the specific reproductive habits and familial cultures of the ashy red colobus at this time.
The decline of red colobus monkey populations signals a decline in the health of an ecosystem, and they are the first species to disappear in highly disturbed habitats.
Indeed, in heavily logged and fragmented areas of Uganda and Tanzania, ashy red colobus populations are significantly lower and have a higher rate of parasitic infection than the population in Kibale National Park, where some of the last old-growth forest in Uganda still stands healthy and intact.
Where the two species live together, ashy red colobuses are regularly hunted by chimpanzees who eat their meat. They are also occasionally found on the menu of crowned eagles.
Red colobus species are the most threatened group of primates in Africa. They are highly vulnerable to forest degradation and are the first to die out in highly disturbed habitat.
Ashy red colobuses are no different. The ashy red colobus is classified as Endangered by the International Union for Conservation of Nature (IUCN, 2019), appearing on the IUCN Red List of Threatened Species.
The forests where ashy reds live are regularly cut down for lumber, converted to farmland, or destroyed in order to mine the land for charcoal. As these practices continue, the ranges of ashy red colobus groups grow smaller and more fragmented. Additionally, their food sources dwindle and become less diverse. As the variation in their diets decreases, their risk of malnutrition increases. This makes individuals generally less healthy and more vulnerable to disease and parasitic infection.
Parasitic infection is considered a key factor in the decline of ashy red populations. Living in such large groups and eating such a large variety of plants makes ashy red colobuses (and other red colobus species for that matter) highly vulnerable to the spread of parasites. Forest degradation only exacerbates this issue. Research has shown that ashy reds living in fragmented forests are affected by parasites at significantly higher levels than those living in intact forest. This is not only because parasites are more abundant in fragmented forests than in healthy intact ones, but also because fragmented forests are also home to more types of parasites. Many of these novel parasites come from the livestock and humans to whom these ashy red groups now live in such close proximity.
Proximity to farms creates other problems for ashy red colobuses as well. With their food sources dwindling, certain populations have taken to leaving the canopy in order to raid local farmers’ bean crops. The farmers do not take very kindly to this behavior and have been known to kill individual monkeys caught on their land, skinning them and leaving their pelts in plain view as a warning to the others. These retaliatory killings are frequently unwarranted, however. Other species of monkeys are also known to raid crops but are more likely to get away with it. These farmers tend to blame ashy reds exclusively, probably because they have been told by conservationists to preserve the last remaining dregs of forest for the sake of these red colobus monkeys specifically.
Ashy red colobuses are also threatened by apes other than humans. Chimpanzees, who prize them for their meat, regularly hunt ashy red colobuses. In several cases, the chimps hunt so frequently that ashy red populations do not have time to recover—especially given that the chimps largely target mothers and infants. While chimpanzees also hunt other monkey species, ashy red colobuses are known to stand their ground during confrontations. This behavior probably puts them in a more vulnerable position when up against such large and aggressive primates. Some researchers believe, however, that as ashy reds become more scarce they will become harder to hunt, forcing the chimps to target other species of monkeys more.
In the past, ashy red colobuses were hunted by humans for their meat and skins. This practice does continue today, but to a much lesser extent than before.
The Red Colobus Conservation Action Plan (or ReCAP) Initiative is a collaboration under IUCN/SSC Primate Specialist Group that aims to stop the decline of all species of red colobus populations, including the ashy red. The initiative brings together experts of all red colobus species and subspecies. Together, and with their pooled expertise, they are working to enhance conservation for all 18 red colobus species and to raise worldwide awareness about their dire situations. They are developing and implementing more effective ways of monitoring and protecting red colobus species, as well as building professional capacity for conservation programs throughout Africa to ensure their continuation.
Unfortunately, the population that lives in Kibale National Park in Uganda is generally considered to be the “last hope” for conservation of the ashy red colobus by conservationists since it is the largest, most viable, and best protected population. Other ashy red populations, such as those inhabiting the Mbuzi and Mbizi forests in Tanzania, are significantly smaller, living in severely fragmented habitat, and have little-to-no protections as they do not live within a conservation area of any kind. Though, that does not mean conservationists have given up on these smaller populations altogether.
A project through the Mohamed bin Zayed Species Conservation Fund, and led by Amani S. Kitegil, is specifically dealing with the small ashy red colobus populations living in the Mbizi and Mbuzi forests in the Rukwa Region of Tanzania. With his group, Kitegel is conducting habitat surveys and animals censuses in the two forests, helping locals to establish more sustainable ways of sourcing their incomes, and facilitating workshops to spread awareness on the importance of red colobus conservation.
Written by Zachary Lussier, July 2019