Search

Primates are affected by fluctuations in ambient temperatures, mostly through thermoregulatory costs and changes in the availability of food. In the present study, we investigate whether the ambient temperature and proxies of food availability affect the activity period of marmosets (Callithrix spp.). We predicted that: (i) at colder sites, marmosets would spend more time at sleeping sites; (ii) midday resting bouts would be longer at hotter sites; (iii) the onset/cessation of activity and resting behavior at midday would be more closely related to temperature than food availability, and (iv) highly exudativorous groups would have higher total levels of resting. We compiled data on the onset and cessation of activity and the time spent resting at midday from seven marmoset studies from sites with a wide range of temperatures. We used generalized linear mixed models to verify the relationship between the dependent variables (lag between dawn and the onset of activities, lag between cessation of activities and dusk, and proportion of resting during midday) and the minimum and maximum temperatures at the respective study sites, together with proxies of food availability (exudativory rates, the amount of habitat available per individual, and net primary productivity) using each sample month as a sampling unit and the identity of the study as a categorical random factor. At colder sites and during colder months, the marmosets left sleeping trees later in the morning and ceased their activities earlier, while at hotter sites and during hotter months, they spent more time resting during midday. More exudativorous groups become active later in the morning, but also ceased their activities later. The abundance of food did not affect the timing of activities. We provide evidence that both low and high temperatures affect marmosets' activities, and that their activity period appears to be more influenced by the thermal environment than food availability., (© 2021 Wiley Periodicals LLC.)

All Neotropical primates are arboreal and thus depend on forests for their survival. Arboreality puts many Neotropical primates at risk of extinction due to the high rates of deforestation in the tropics. We assessed the influence of vegetation structure and forest patch attributes on the occurrence of the threatened red-handed howler monkey (Alouatta belzebul) in an Amazonian savanna. Using a sample of 38 forest patches in a region of approximately 2000 km 2 in the state of Amapá, northern Brazil, we used logistic regression to find the best predictors of the occurrence of A. belzebul. We assessed patch area, patch isolation, the proportion of seasonally flooded forest in the patch, the density of flooded area palms, forest height, canopy cover, and diameter at breast height of trees. Patch area and palm density were the best predictors of the occurrence of A. belzebul in forest patches, both having a positive effect on the probability of occurrence. Our results indicate that areas of flooded forest in forest patches may be keystone habitats for A. belzebul living in Amazonian savannas. The observed effect of palm density on A. belzebul suggests that this variable is useful for planning conservation actions, including the selection of areas for protection and management strategies for areas inhabited by this primate., (© 2020 Wiley Periodicals LLC.)

Understanding the effects of habitat structure and other environmental variables on the density of a species can help define its habitat preferences and key ecological determinants of population parameters. The present study evaluated the effects of fragment size, the presence of a key predator/competitor, the yellow-breasted capuchin (Sapajus xanthosternos), primary productivity, the abundance of bromeliads, and habitat structure on the population density of the common marmoset (Callithrix jacchus). A total of 21 fragments were surveyed within a 350-km long zone of coastal Atlantic Forest representing the southern extreme of the distribution of the species in the Brazilian Northeast. An index of marmoset density was generated for each site based on playback surveys. The relationship between the density of marmosets and a set of parameters was evaluated by multiple regression. A Principal Components Analysis (PCA) condensed the five variables of habitat structure into two principal components, which contained 85% of their combined variation. The model that best explained the density of marmosets (R(2) = 59.1) contained the second PCA component and the presence/absence of capuchins. The analysis indicated that the marmosets prefer forests with denser understory, whether or not they are secondary habitats. The negative effect of the presence of capuchins may be related to predation pressure. The results of this study indicate that multiple-site studies may provide important insights into the habitat preferences of primate species and the factors that affect their population density., (© 2014 Wiley Periodicals, Inc.)

Activity budgets are widely used in primate behavioral studies for the analysis of ecological strategies. In some cases, there is considerable seasonal variation in the length of the daily activity period. Here, activity budgets from two field studies of Callithrix flaviceps were compiled first by the traditional approach (proportion of scan sample records) and then by considering the proportion of time dedicated to each activity over the 24-hr cycle (adjusted budget). Both groups were almost invariably active for at least 1-2 hr less than the daylight period, with significantly shorter activity periods during the austral winter, when the daylight period was up to 2:35 hr shorter than in the summer. The adjustment of activity budgets provided a completely different perspective on foraging strategies. Whereas the basic budgets indicated a significant increase in foraging and moving during the resource-poor dry season (winter) months, the time-adjusted data revealed that the primary strategy was a time-minimizing one, with the animals simply spending more time at rest during the longer activity periods of summer days. While both groups followed the same pattern of relatively short activity periods, there were considerable differences between sites in the mean duration of the period in a given month, and in behavior patterns, although the analysis of the determining factors was beyond the scope of the present study. Overall, the results of the study indicate that the manipulation of the duration of the daily activity period may be an integral component of primate behavioral strategies, and that this parameter should be taken into account systematically when evaluating activity patterns, especially at sites at relatively high latitudes where day length may vary considerably over the course of the year., (© 2013 Wiley Periodicals, Inc.)

Mycophagy is a relatively rare behavior in primates and has only been recorded in five callitrichid species. Here, we present data on the feeding ecology of a free-ranging group of Callithrix flaviceps, which was studied in the Augusto Ruschi Biological Reserve, Southeastern Brazil, in 2008. In contrast with other marmosets, which are typically gummivorous, the study group was predominantly mycophagous-insectivorous, with fungi corresponding to 64.8% of total feeding records, and gum (6.1%) and fruit (3.3%) together providing only a minor part of the diet. Prey corresponded to 25.8% of the group's diet. The fungi (Mycocitrus spp.) consumed by the marmosets were found attached to the stems of Merostachys bamboo. As the animal component of the group's diet was similar to that recorded in studies of other marmosets, we propose that fungi were exploited primarily as a substitute for plant material, in particular exudates. This highly mycophagous diet may be determined by two principal factors: (1) the abundance of fungi within the study area, and (2) the avoidance of bark gouging, for which C. flaviceps may be less specialized than most other marmosets. These conclusions are supported by comparisons with other marmoset groups, which indicate an ecological specialization for mycophagy in C. flaviceps, and that the species will resort to gummivory in habitats where fungi are scarce.