Christini B. Caselli

Estimating primate population densities: the systematic use of playbacks along transects in population surveys.

Accurate measures of animal population densities are essential to assess their status, demography, and answer ecological questions. Among several methods proposed to collect abundance data, line transect sampling is used the most. The assumptions required to obtain accurate density estimates through this method, however, are rarely met when studying primates. As most primate species are vocally active, density estimates can be improved by associating transect sampling with playback point counts to scan the entire study area. Yet, attention to playback procedure and data collection design is necessary. Here, we describe a protocol to assess primate densities using playback and test its application on surveys of Callicebus nigrifrons, a small Neotropical primate that shows site fidelity and active vocal behavior. We list important steps and discuss precautions that should be considered, from the adjustments in the recordings in the lab to field procedures in the playback broadcasting sessions. Prior to the surveys, we conducted playback trials with three habituated wild groups at three forest remnants to test their response to the playback stimuli at different distances. Based on these trials, we defined the radius distance covered by the playback sessions. Then, we conducted two surveys in 12 forest remnants, in the northeast of São Paulo State Brazil. The results of density estimates were consistent between the two surveys. As the playback survey protocol we described has proved to be a simple and useful tool for surveying vocal primate and generated reliable data, we suggest that it is a good alternative method to estimate density of species, particularly for those that are responsive to playbacks and show site fidelity.

Evolutionary Biology and Conservation of Titis, Sakis and Uacaris: Why we know so little: the challenges of fieldwork on the Pitheciids

Introduction Possessing a suite of unusual and interesting features, Pitheciids are at the extremes of many of primatology’s ecological and sociological continua (see Norconk 2011). Pitheciids should provide acute tests of many primatological models; however, this is frequently thwarted by the lack of even the most basic quantitative information concerning ecology, behavior and social organization. Such gaps are due not only to the small number of studies, but also to difficulties in obtaining data. This chapter considers why, given that these primates possess such aesthetic and intellectual appeal and high conservation value, they have been so little studied. The peculiarities of pitheciids, combined with their native habitats’ inherent challenges, have often undermined potentially successful fieldwork. Some researchers who began working with species of Callicebus or Chiropotes, for example, simply gave up because of problems habituating the animals or because the study was so difficult that the quality and quantity of gained data would not be worth the effort. Several researchers who persisted were either unable to obtain the expected volume of data or were incapable of answering many of their initial research questions, sometimes both. Using field experiences from a variety of research projects across a range of habitat types and pitheciid taxa, this chapter reports on the problems that arose during these studies and presents suggestions to minimize similar difficulties in the future.

Geographic comparison of plant genera used in frugivory among the pitheciids Cacajao, Callicebus, Chiropotes, and Pithecia.

Pitheciids are known for their frugivorous diets, but there has been no broad‐scale comparison of fruit genera used by these primates that range across five geographic regions in South America. We compiled 31 fruit lists from data collected from 18 species (three Cacajao, six Callicebus, five Chiropotes, and four Pithecia) at 26 study sites in six countries. Together, these lists contained 455 plant genera from 96 families. We predicted that 1) closely related Chiropotes and Cacajao would demonstrate the greatest similarity in fruit lists; 2) pitheciids living in closer geographic proximity would have greater similarities in fruit lists; and 3) fruit genus richness would be lower in lists from forest fragments than continuous forests. Fruit genus richness was greatest for the composite Chiropotes list, even though Pithecia had the greatest overall sampling effort. We also found that the Callicebus composite fruit list had lower similarity scores in comparison with the composite food lists of the other three genera (both within and between geographic areas). Chiropotes and Pithecia showed strongest similarities in fruit lists, followed by sister taxa Chiropotes and Cacajao. Overall, pitheciids in closer proximity had more similarities in their fruit list, and this pattern was evident in the fruit lists for both Callicebus and Chiropotes. There was no difference in the number of fruit genera used by pitheciids in habitat fragments and continuous forest. Our findings demonstrate that pitheciids use a variety of fruit genera, but phylogenetic and geographic patterns in fruit use are not consistent across all pitheciid genera. This study represents the most extensive examination of pitheciid fruit consumption to date, but future research is needed to investigate the extent to which the trends in fruit genus richness noted here are attributable to habitat differences among study sites, differences in feeding ecology, or a combination of both. Am. J. Primatol. 78:493–506, 2016.

Sleeping above the enemy: Sleeping site choice by black-fronted titi monkeys (Callicebus nigrifrons)

The costs imposed by predation may result in behavioral adaptations to reduce mortality risk, including the choice and use of sleeping sites. The threat of predation, however, is rarely the sole force shaping sleeping site choice, which is likely to reflect other factors such as foraging needs as well. Here we describe the use of sleeping sites by three groups of small Neotropical monkeys, the black‐fronted titi monkeys (Callicebus nigrifrons), and evaluate the role of predation pressure and foraging optimization in their choice of sleeping sites. We monitored each group for 9–20 months at two Atlantic Forest sites in southeastern Brazil. The titi monkeys used taller and larger trees to sleep than the average trees at each study site and chose branches with high vegetation coverage and located in higher forest strata than those used during diurnal activity. Sleeping sites were randomly distributed within each groups home range, and the groups avoided using the same site on consecutive nights. The characteristics of the sleeping sites and the behavior of the titi monkeys suggest that predation avoidance, especially of scansorial carnivores, is an important factor driving sleeping site choice. We conclude that titi monkeys’ strategy to avoid predation while sleeping depends on the presence of a heterogeneous forest stratum with large emergent trees and liana tangles, which offer a physical barrier against predators.