Titi monkeys, Callicebus, comprise the most species-rich primate genus—34 species are currently recognised, five of them described since 2005. The lack of molecular data for titi monkeys has meant that little is known of their phylogenetic relationships and divergence times. To clarify their evolutionary history, we assembled a large molecular dataset by sequencing 20 nuclear and two mitochondrial loci for 15 species, including representatives from all recognised species groups. Phylogenetic relationships were inferred using concatenated maximum likelihood and Bayesian analyses, allowing us to evaluate the current taxonomic hypothesis for the genus. Our results show four distinct Callicebus clades, for the most part concordant with the currently recognised morphological species-groups—the torquatus group, the personatus group, the donacophilus group, and the moloch group. The cupreus and moloch groups are not monophyletic, and all species of the formerly recognized cupreus group are reassigned to the moloch group. Two of the major divergence events are dated to the Miocene. The torquatus group, the oldest radiation, diverged c. 11 Ma; and the Atlantic forest personatus group split from the ancestor of all donacophilus and moloch species at 9–8 Ma. There is little molecular evidence for the separation of Callicebus caligatus and C. dubius, and we suggest that C. dubius should be considered a junior synonym of a polymorphic C. caligatus. Considering molecular, morphological and biogeographic evidence, we propose a new genus level taxonomy for titi monkeys: Cheracebus n. gen. in the Orinoco, Negro and upper Amazon basins (torquatus group), Callicebus Thomas, 1903, in the Atlantic Forest (personatus group), and Plecturocebus n. gen. in the Amazon basin and Chaco region (donacophilus and moloch groups).

Monkeys first arrived in the Neotropics about 36 Ma, and the ancestry of all living Neotropical primates (Platyrrhini) traces to a single common ancestral population from 24 to 19 Ma. The availability of lush Amazonian habitat, the rise of the Andes, the transition from the lacustrine to riverine system in the Amazon Basin, and the intermittent connection between the Amazon and the Atlantic tropical forests have all shaped how primates spread and diversified. Primates outcompeted native South American mammals but faced an influx of North American fauna with the closing of the Isthmus of Panama. Humans, extreme newcomers in the Neotropics, have influenced primate habitat and ecology over the last 13,000 years, with radical transformations in the last 500 years as a result of European colonization and land use change. Neotropical primate biogeography informs taxonomic work and conservation efforts, with a mind toward mitigating effects of direct human impact and human-mediated climate change.

Oculocutaneous Albinism (OCA) is an autosomal recessive inherited condition that affects the pigmentation of eyes, hair and skin. The OCA phenotype may be caused by mutations in the tyrosinase gene (TYR), which expresses the tyrosinase enzyme and has an important role in the synthesis of melanin pigment. The aim of this study was to identify the genetic mutation responsible for the albinism in a captive capuchin monkey, and to describe the TYR gene of normal phenotype individuals. In addition, we identified the subject’s species. A homozygous nonsense mutation was identified in exon 1 of the TYR gene, with the substitution of a cytosine for a thymine nucleotide (C64T) at codon 22, leading to a premature stop codon (R22X) in the albino robust capuchin monkey. The albino and five non-albino robust capuchin monkeys were identified as Sapajus apella, based on phylogenetic analyses, pelage pattern and geographic provenance. One individual was identified as S. macrocephalus. We conclude that the point mutation C64T in the TYR gene is responsible for the OCA1 albino phenotype in the capuchin monkey, classified as Sapajus apella.

Wild capuchin monkeys are highly adaptable to anthropogenic environments. We assessed how the interaction dynamics between humans and three groups of Panamanian white-faced capuchin monkeys (Cebus imitator) in Manuel Antonio National Park, the most visited national park of Costa Rica, affected the feeding behavior and diet of these animals in 2008-2009. On average, individual monkeys acquired 2.4 human food items per focal hour during peak hours of park visitation by humans. Although human visitors directly and indirectly provisioned monkeys in the park, 71 % of monkeys’ acquisition of human food items were a result of monkey-initiated interactions (MIIs) rather than human-initiated interactions (HIIs), and adult male monkeys were the most frequent initiators (with 157 adult male MIIs in the study period, compared to 33 initiated by adult females and 84 by juveniles). Adult male monkeys were also the most likely to make direct contact with humans to grab food (35 of 50 direct grabs of food from humans were by adult male monkeys). Adult females acquired food from humans through HIIs at about the same rate as adult males in their group. Secondary acquisition of human food from other monkeys accounted for about one-third of all events of monkey acquisition of human food, and juvenile monkeys had higher median hourly rates than adults in their group to acquire human food through secondary acquisition. Humans frequently offered fruit when provisioning (61.4 % of provisioning events), but monkeys actively acquired fruit, meat, candy, condiments, chips, crackers and dairy items, and only 36.5 % of MIIs were to acquire fruit. Our results suggest that in parks where humans have frequent contact with capuchin monkeys, park regulations should not only prohibit direct provisioning, but require visitors not to bring food into parks. Stronger measures such as fines or park expulsion for those interacting with monkeys might be more effective, and environmental education is necessary as a strategy to inform visitors what to expect from the monkeys and how to avoid accidental provisioning.