The Rio Mayo titi (Plecturocebus oenanthe ) is a species of titi, a type of New World monkey, endemic to Peru. The Rio Mayo titi, was thought previously to have a small range of origin in the Alto Mayo valley, but research has proven that the range extends southward and reaches the Huayamba River, as well as Bajo Mayo. It had been classified as vulnerable but due to major habitat loss and restricted living space, it is now classified as Critically Endangered. In October 2012, it was included in The World's 25 Most Endangered Primates list. An increase in deforestation is leading to the decrease in available living space for this titi monkey, forcing it to live in sympatry with another species of Callicebus. Yet in some areas, such drastic deforestation has resulted in extremely high population density. The Rio Mayo titi is better adapted to moderately populated areas, thus overpopulation negatively impacts the species. The forests the Rio Mayo titi lives in are being destroyed for agricultural purposes, leaving little forest for the monkeys. They were only seen a few times and featured in museums until 2003 when more research was done on them. In order for this species to survive, their forests need to be protected to avoid overpopulation. Different conservation groups are working to help P. oenanthe survive. Neotropical Primate Conservation, Proyecto Mono Tocón and Amazónicos para la Amazonia are working in the more southern areas to protect the monkey.The Rio Mayo titi is a fairly inconspicuous creature, making observation and research difficult to obtain. Therefore, the traditional use of transect observation to monitor the monkey's population, is less effective. Instead, other methods of calculating the titi monkey's density in certain areas have been taken, such as research into the species-specific calls endemic to a certain area.
The appearance of the Rio Mayo titi varies based on their location. In one part of Ecuador, the titis were seen to have reddish brown fur on their back, limbs and chest and lighter reddish brown fur in the on the outside of their limbs. They had a dark brown-red forehead, sideburns and beard and small white tufts of fur coming out of their ears. They had a light colored throat, black hands, tail and nails and cream colored underparts with white hairs on their muzzle. Their fur was short and spikey. In another part of Ecuador, the titis had a light red fur on their forehead, sideburns and beard, quite a lot of fur by their ears, dark hands with white fur on them, red underparts and chest, a gray tail and whitish hair above their nose, eyebrows and muzzle. Their fur was frizzy.
The diet of the Rio Mayo titi consists of mostly leaves, seeds, fruits, and arthropods. In one study, it was found that 54% of their diet was fruit, and 22% insects (consisting of at least 10 different types of insects), with the remainder consisting of leaves, tendrils, meristems, flowers and seeds.
The 22% of the P. oenanthe diet that consists of insects is gathered in a variety of ways. There are three main types of foraging technique that the species uses to catch insects: lunging and grabbing exposed prey, biting and inspecting hidden prey, and stealth foraging or scanning for prey. Out of the three techniques, the most frequently used technique for hunting insects was found to be lunging and grabbing exposed prey. They have a high success rate of catching insects, reaching up to 83%. This species' ability to hunt insects so easily is especially important for survival in times of scarce food availability.
After discovering the distribution of the species and where it primarily lives, the next step in conserving it is determining the densities of the species, creating protected areas specifically for this animal, and expanding existing ones. To find the density of the P. oenanthe, a triangulation method is used, where three points are set up and the species is observed within the area created by these points. While density was measured by using this method and also examining the trees by their density, height, and distance from one another, human disturbance is also monitored. This study described was performed in Ojos de Agua in Guanajuato, Mexico. This study was part of a larger study created by Program Management Team (PMT) to study the habitat requirements of P. oenanthe and exploring the possibility of creating corridors between species fragmented distributions.
