Besides its extreme climate conditions, the Caatinga (a type of tropical seasonal forest) hosts an impressive faunal and floristic biodiversity. In the last 50 years there has been a considerable increase in the number of studies in the area. Here we aimed to present a review of these studies, focusing on four main fields: vertebrate ecology, plant ecology, human ecology, and ethnobiology. Furthermore, we identify directions for future research. We hope that the present paper will help defining actions and strategies for the conservation of the biological diversity of the Caatinga.

BackgroundSocial conformity is a cornerstone of human culture because it accelerates and maintains the spread of behaviour within a group. Few empirical studies have investigated the role of social conformity in the maintenance of traditions despite an increasing body of literature on the formation of behavioural patterns in non-human animals. The current report presents a field experiment with free-ranging marmosets (Callithrix jacchus) which investigated whether social conformity is necessary for the maintenance of behavioural patterns within groups or whether individual effects such as habit formation would suffice.MethodsUsing a two-action apparatus, we established alternative behavioural patterns in six family groups composed of 36 individuals. These groups experienced only one technique during a training phase and were thereafter tested with two techniques available. The monkeys reliably maintained the trained method over a period of three weeks, despite discovering the alternative technique. Three additional groups were given the same number of sessions, but those 21 individuals could freely choose the method to obtain a reward. In these control groups, an overall bias towards one of the two methods was observed, but animals with a different preference did not adjust towards the group norm. Thirteen of the fifteen animals that discovered both techniques remained with the action with which they were initially successful, independent of the group preference and the type of action (Binomial test: exp. proportion: 0.5, p<0.01).ConclusionsThe results indicate that the maintenance of behavioural patterns within groups 1) could be explained by the first rewarded manipulation and subsequent habit formation and 2) do not require social conformity as a mechanism. After an initial spread of a behaviour throughout a group, this mechanism may lead to a superficial appearance of conformity without the involvement of such a socially and cognitively complex mechanism. This is the first time that such an experiment has been conducted with free-ranging primates.

In this study we investigated the extent and pattern of social influences (i.e., the use of a conspecific as a model) on the foraging behavior of immature, wild common marmosets (Callithrix jacchus) as a function of the age of individuals. We compared the foraging activities and interactions with subadult and adult group members (older than 15 months) of young infants (1-2 months old), older infants (3-4 months old), and juveniles (5-10 months old). In addition to measuring the intensities of model-independent foraging (MIF) and merely paying attention to the model's foraging activities, we examined the frequencies of three types of model-dependent foraging (MDF): "follow the model", "manipulate the same object", and "forage together". We found that older infants were the most attentive and most socially-influenced foragers among the three age categories in absolute terms, but were not more attentive than young infants given their low foraging activity. Juveniles, in contrast, tended to have reduced overall foraging intensity compared to infants, but showed relatively more MDF in cases in which they observed subadult or adult models. Female models appeared to be more attractive than male models. These findings suggest that infants are generally more attentive to the foraging behavior of subadults and adults than juveniles, with the latter being more influenced when they had observed a model before. These subtle age-dependent effects of social foraging not only extend the assumption that young primates seek information from adults, they also suggest a complex interplay among physical and cognitive maturation, independence, and social dynamics.

Callithrix jacchus are small-bodied Neotropical primates popularly known as common marmosets. They are endemic to Northeast Brazil and occur in contrasting environments such as the humid Atlantic Forest and the dry scrub forest of the Caatinga. Common marmosets live in social groups, usually containing only one breeding pair. These primates have a parental care system in which individuals help by providing assistance to the infants even when they are not related to them. Free-ranging groups use relatively small home ranges (0.5-5 hectares) and have an omnivorous diet. Because of the shape of their teeth, they actively gouge tree bark to extract and consume exudates. When foraging for live prey, they adjust their strategy according to the type of prey. The successful use of appropriate hunting strategies depends not only on age but also on prey type and seems to be mediated by learning and experience. Indeed, common marmosets have shown unexpected cognitive abilities, such as true imitation. All these aspects seem to have contributed to the ecological success of this species. Callithrix jacchus has been widely studied, especially in captivity; even so, a number of questions remain to be answered about its biology, ecology, and behavior, both in captivity and the wild. A richer understanding of marmosets' natural behavior and ecology can have a significant impact on shaping ongoing and future neuroscience research. © 2016 Wiley Periodicals, Inc. Develop Neurobiol 77: 244-262, 2017.

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.