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We provide here a current overview of marmoset (Callithrix) evolution, hybridization, species biology, basic/biomedical research, and conservation initiatives. Composed of 2 subgroups, the aurita group (C aurita and C flaviceps) and the jacchus group (C geoffroyi, C jacchus, C kuhlii, and C penicillata), this relatively young primate radiation is endemic to the Brazilian Cerrado, Caatinga, and Atlantic Forest biomes. Significant impacts on Callithrix within these biomes resulting from anthropogenic activity include (1) population declines, particularly for the aurita group; (2) widespread geographic displacement, biological invasions, and range expansions of C jacchus and C penicillata; (3) anthropogenic hybridization; and (4) epizootic Yellow Fever and Zika viral outbreaks. A number of Brazilian legal and conservation initiatives are now in place to protect the threatened aurita group and increase research about them. Due to their small size and rapid life history, marmosets are prized biomedical models. As a result, there are increasingly sophisticated genomic Callithrix resources available and burgeoning marmoset functional, immuno-, and epigenomic research. In both the laboratory and the wild, marmosets have given us insight into cognition, social group dynamics, human disease, and pregnancy. Callithrix jacchus and C penicillata are emerging neotropical primate models for arbovirus disease, including Dengue and Zika. Wild marmoset populations are helping us understand sylvatic transmission and human spillover of Zika and Yellow Fever viruses. All of these factors are positioning marmosets as preeminent models to facilitate understanding of facets of evolution, hybridization, conservation, human disease, and emerging infectious diseases.

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As observações ocorreram no período de dois anos, monitorando grupos marcados de sagüis durante oito horas por dia. Foram registrados seis tipos de eventos: predação de sagüis; predação de aves, disputa de área de forrageio e recurso alimentar; compartilhamento de área de forrageio e recurso alimentar; perseguição branda e utilização de ninho de ave como local de pernoite dos sagüis. Os eventos agrupados obtiveram diferenças significativas entre as estações do ano e os estratos ocupados.

Animals must overcome the physical properties protecting foods to obtain nutrition. While animals can experience selection for traits that facilitate resource exploitation, specific feeding behaviors may entail multiple, different mechanical challenges with each potentially eliciting distinct selection pressures. Tree gouging by common marmosets (Primates: Callithrix jacchus) provides an illustrative case for studying these distinct mechanical challenges and their correlated behaviors and morphologies. We test the hypothesis that marmosets respond differently to three sequential mechanical stages of bark removal: (1) indentation; (2) crack initiation; (3) crack propagation. By surveying trees gouged by free‐ranging marmosets in Pernambuco, Brazil, we found that mechanical variables related to crack initiation (fracture toughness, critical strain energy release rate and elastic modulus) were inversely correlated with measures of gouging intensity, with less mechanically challenging trees being gouged more intensely. Because crack initiation is likely the most mechanically challenging aspect of tree gouging, behavioral preference for less challenging resources likely allows marmosets to reduce costs and potential risks associated with accessing exudates. Variables related to bark indentation (hardness and friction) showed no relationship to the intensity of gouging behavior. Contrary to our prediction, trees with greater mechanical challenges for crack propagation (work to peel) were gouged more intensely. We attribute this pattern of gouging trees requiring greater effort in crack propagation to an inverse correlation between work to peel and fracture toughness in our tree sample. Importantly, marmosets exhibit morphological specializations of the feeding apparatus that facilitate indentation and crack propagation, potentially mitigating the need for behavioral choice. Here we show that extracting a single food resource can exert a series of distinct, potentially competing, selective forces during resource acquisition. This study illustrates how animals combine behaviors and morphological specializations to competently overcome distinct mechanical challenges, emphasizing the need for holistic approaches in understanding feeding adaptations.