A Life in Fragments: The Ecology, Behavior, and Conservation of the Recently Described Parecis Plateau Titi Monkey (Plecturocebus parecis)

While some South American primates are well-studied, many are poorly known to science. This makes reports of their ecology very valuable, especially when the region inhabited is threatened by human activities. We combined data from three independent field studies to provide a better understanding of the behavior, ecology, chemical composition of plant items consumed, and conservation of the Parecis Plateau titi monkey ( Plecturocebus parecis ), a recently described species from the southern Amazonian Arc of Deforestation. Specifically, we collected behavioral data for eight groups over 8 months and quantified the monkeys’ activity budget. To analyze the chemical compounds in the plants eaten, we used vanillin to determine condensed tannin and alkaline precipitation to quantify total alkaloid content. We also determined the extent of forest loss and fragmentation from 2000 to 2019 within the known range of the Parecis Plateau titi monkey using satellite imagery. We found that group size ranged 2–6 individuals, and the monkeys spent 31% of the day foraging, 22% resting, 19% feeding, 14% moving, and 14% in other activities. The monkeys ate 50 plant species from 24 families and appeared to be unusually tolerant of dietary tannins but avoided alkaloids. Habitat modification within the species’ range has been extensive: forest cover declined by 16.1% in 2000–2019; the largest areas of continuous forest were reduced by 37.5%; mean fragment size decreased 67.5% (from 421.0–136.9 ha). Forest loss and fragmentation were most significant in the northern half of the species’ range and its southern border. Given the Parecis Plateau titi monkey’s tolerance for toxic dietary species, the intense modification of its geographic range, and its capacity to live in fragmented habitats, we recommend that future studies investigate these topics across all 37 species of titi monkeys. In addition, recordings of vocal repertoires will improve field surveys and help with population estimates, especially for titi monkey species living in geographic regions that have been heavily modified by humans.