Occasional Field Observations of the Predation on Mice, Dove and Ants by Black-Tufted-Ear Marmosets (Callithrix penicillata)

An Introduction to the Callithrix Genus and Overview of Recent Advances in Marmoset Research

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.

Predation of army ants by Toppin's titi monkey, Plecturocebus toppini Thomas 1914 (Primates: Pitheciidae), in an urban forest fragment in eastern Acre, Brazil

The predation of army ants (Eciton rapax) was recorded during an observational study of the feeding behavior of a group of titi monkeys (Plecturocebus toppini) in an urban fragment of forest in Acre, Brazil. During one observed event, the group's adult female used its tail to retrieve ants, a type of behavior not observed previously in this genus. All incidents of on-forest floor foraging occurred during the dry season, when fruit was least abundant in the forest, while on other occasions, the ants were captured from tree branches and leaves. The observation of predation and ground-level foraging recorded in this study reinforce the adaptive capacity of P. toppini for survival in fragmented forests, and this was also the first record of the predation of army ants by this titi species.

Scratching under positive and negative arousal in common marmosets (Callithrix jacchus)

Scratching has been widely used as an indicator of anxiety in many primate species. However, a handful of studies have shown no change in scratching under anxiety-provoking circumstances. In addition, the existing literature has investigated scratching only in relation to negative arousal (i.e., anxiety), even though anxiety and excitement (positive arousal) share important physiological and behavioral correlates, including increased heart rate, blood pressure, and locomotion. In the current study, we scored all instances of scratching in 11 outdoor-housed captive common marmosets (Callithrix jacchus) during three contexts that were intended to be negatively arousing and three contexts that were intended to be positively arousing during a baseline, manipulation, and post-induction period. Summed across the three negative arousal contexts, the results showed that subjects exhibited significantly lower scratching rates during the manipulation than during either the baseline or post-induction periods, and the pattern of means was the same for all three of those contexts. Under the three contexts of positive arousal, subjects exhibited different patterns of scratching rates during the manipulation periods (play = increases, foraging = decreases, food anticipation = no change). Data from the current study, and a close examination of data from studies showing no change in scratching under anxiety-provoking circumstances, suggest that the anxiety-scratching relationship may be more complex than has been reported previously. Our results raise a potential concern about the unchallenged use of scratching as a behavioral indicator of anxiety in captive non-human primates, with important implications for welfare and management of these species.