Several species of callitrichines (tamarins, marmosets, and callimicos) are reported to frequently leap between vertical supports when foraging and traveling in the forest understory. In the present study, we examine trunk-to-trunk leaping in a wild group of four habituated adult saddleback tamarins (Saguinus fuscicollis weddelli) in northern Bolivia. From June through July, 2011 we analyzed 200 leaps in which the tamarins moved between vertical supports. On average, takeoff height was 4.1 m (±1.3 m, range 1–7.5 m). During the airborne phase of travel the monkeys lost an average of 0.5 m (±0.5 m) at contact with the landing support, and the mean distance leapt was 1.4 m (± 0.7 m). We found no correlation between the diameter at breast height (DBH) of landing and takeoff supports, and either the distance leapt or height gained/lost during leaping. Across callitrichine taxa, it appears that ecological distinctions in diet, patterns of habitat utilization, and predator avoidance strategies have played an important role in understanding the frequency and context of trunk-to-trunk leaping behavior.

In order to review the distribution and status of the Chacoan or white-coated titi monkey in Bolivia, I examined 60 available records of Callicebus and the vegetation types where they occurred in southern Santa Cruz. Based on the color pattern of photographed individuals, their location and basic ecological data, I characterized the range of Callicebus pallescens as extending from the Río Parapetí, across most of the Kaa Iya Park up to the Pantanal of Rio Negro, and inhabiting semiarid Chaco forests (475 mm of rainfall) with tree-like cacti, dry transitional Chaco and Chiquitano forests (<625–800 mm), up to subhumid seasonally flooded riverine forests of the Pantanal (1,000 mm). In the subhumid and humid forests North of Kaa Iya and near Santa Cruz city, C. pallescens is replaced by the gray titi monkey C. donacophilus, which can be recognized by a darker and more contrasting color pattern. However, the geographic limit between the two species is poorly known and confounded by current deforestation. Likewise, the identity of Callicebus from the eastern Chiquitano forest and Pantanal in the Bolivia-Brazil border is also confusing and needs to be studied.

We present data on encounter rates and group sizes of primates in the Lower Urubamba Region of Peru, an unprotected area little represented in the literature. We censused a total of 467.7km on 10 transects during two seasons and documented nine primate species in the area. Compared to nearby protected areas, group encounter rates were lower and group sizes were smaller for all species except Saguinus fuscicollis and S. imperator. Relatively high abundance of S. imperator and low abundance of larger bodied primates is a possible example of density compensation resulting from hunting pressure. In addition to the primates, 23 other mammal species were observed or photographed by camera traps, including Procyon cancrivorus, which was not previously reported in the area.