This is the San Martin titi, or Plecturocebus oenanthe.
It is a small primate, characterised by a light-coloured facial fringe, a dark brown agouti body and limbs, and an orange underside. Its fur is exceptionally thick, giving it a hunched appearance.
The San Martin titi is shy, and has been little studied. It is classified as critically endangered, but its population size has never been estimated.
The species inhabits pre-montane forest up to 1000 meters in the San Martín Region, on the eastern side of the northern section of the Andes. The land here is highly disturbed. The region has suffered intense human colonisation over the last 40 years because of a major agrarian programme, which has attracted huge numbers of immigrants. Much of the titi’s range has been condensed to pockets of secondary and remnant forest fragments surrounded by human activity. Despite this close proximity, it is generally highly intolerant of humans.
Titis normally live in small, monogamous family groups ranging from 2 to 5 individuals, but San Martin titi groups are somewhat larger, as suitable forest has been reduced and the young are less likely to leave to establish their own groups. In some parts of its range it may seem abundant, but this is thought only to be a result of habitat contraction.
All titi species tend to bond closely. Group-mates are rarely found more than a few meters apart from one another, and show clear signs of distress when separated. Individuals sitting next to each other will twine their tails together, in a behaviour that is thought to be as important as mutual grooming in maintaining social ties.
All group members participate in the care of infants, but particularly the fathers, who spend more time carrying infants than any other family member. Relations tend to be peaceful, and serious fighting rarely occurs.
From the ground, San Martin titis are seldom seen, but they are a highly vocal species. They are one of the only mammals to display such complex vocalisations as “singing” and “duetting” - another being the indri (Indri indri).
In the absence of reliable visual observations, scientists studying the San Martin titi in one area have used these vocalisations to deduce various aspects of the species’ population density, group size, and social relations. This method of study had only previously been used for species of birds.
In an indication of just how disturbed this particular fragment of titi habitat was, sounds related to human activity can be heard in much of the audio data they collected. In one typical 30-minute daytime sound recording, chainsaws were clearly audible for 22% of the segment, motorboats for 11%, and explosions from gunshot and fireworks for 6%. At night, music carried upriver from the nearby towns. In the same study, frequent smoke from agricultural fires was also reported.
In this region, it is estimated that up to one seventh of the land cleared for crop-growing is subsequently abandoned due to low productivity. The soil is just not conducive to intensive agriculture. Some of this land has been purchased by conservation groups and restored to forest, but more than 30,000 hectares of agricultural wasteland remain.
The destruction also continues - the region is becoming increasingly inhabited, land is continuously cleared, and existing roads are paved and extended.
