The conservation status of A. palliata, commonly referred to as black mantled howler monkey, is vulnerable in Colombia because of its decline in population. The distributional limit in the northeast of the country is not well defined and the dry forests of the north of the country are being destroyed at alarming rates. In the municipality of El Guamo (Bolívar) less than 20% of the landscape is composed of forests. The two largest remnants of forests in the municipality have extensions of 3,544.7 and 879.6 ha each. From interviews with the community, I concluded that habitat loss is the main threat to primate populations. 37.6 % of the community of inhabitants said they had seen the monkey in the municipality of Guamo, however, I found no A. palliata during a short transect sampling. Individuals of the species Alouatta seniculus and Saguinus oedipus were detected during these walks. Conservation actions such as reforestation, establishment of agroforestry systems and corridors designed to improve the habitat of A. palliata should encourage the participation of the human communities.

Brazil contains 1/3 of the world's remaining tropical forests and is recognized as one of the world's most important storehouses of biodiversity. With regard to primate species richness, it is especially prominent. There are 133 species and subspecies in Brazil – of these 80 occur in the Brazilian Amazon and 11 are in danger of extinction. In spite of these impressive numbers, there is little ecological or population data available for many of these species, especially those that occur in the Amazon. To address this lack, the objectives of this study were to: 1) record occurring primate species; 2) estimate their population densities; and 3) characterize their distributions in the Adolpho Ducke Forest Reserve. This reserve, situated on north of Manaus in the state of Amazonas, Brazil, contains 10,000 hectares of primary forest. The data were collected using linear transects, covering the entire system of trails within the reserve. In a total of 720 km of trails walked, 58 sightings were registered of Saguinus bicolor, 29 of Cebus apella, 20 of Alouatta seniculus, 13 of Pithecia pithecia and 10 of Chiropotes sagulatus. Sightings occurred in all types of environments (plateau, slope, and lowland). S. bicolor had the greatest density (1.00 group/km²), followed by C. apella (0.67), A. seniculus (0.66), P.pithecia (0.64) and C. sagulatus (0.30). The resulting estimate of groups present in the total reserve area, not considering possible gaps, natural habitat variation, or resource availability, is 100 groups of S. bicolor, 67 of C. apella, 66 of A. seniculus, 64 of P. pithecia and 30 of C. sagulatus. These results demonstrate the importance of the Adolpho Ducke Forest Reserve for the maintenance of biodiversity and emphasize the need for targeted conservation policies to contain anthropogenic disturbances in the region.

Here we present the results of a population survey of the black-faced lion tamarin, Leontopithecus caissara, on Superagüi Island, and we extrapolate this estimation to the entire population. We used the linear transect method for surveys of the area from November 2000 to January 2002. When lion tamarins were seen in transects, we noted the perpendicular distance from the path and the number of individuals sighted in a cluster. Using the software Distance 4.0 we estimated a density of 1.79 individuals/km² and a population of 205 individuals (95% CI: 79 – 537 ind/km²) on the Superagüi Island. The extrapolation of these results to populations on the mainland gave us an estimate of 187 individuals (95% CI: 72 – 489 ind/km²). Our estimate for the total population is 392 individuals (95% CI: 218 – 1,026 ind/km²). The lower population density of L. caissara compared to other species of the genus, in combination with its very small geographic range, indicate that it is critically endangered. We also discuss some aspects of the limitations of the linear transect method when densities are extremely low. The Distance 4.0 software suggested a minimum of 30 sightings for a density estimate; but from the sighting frequency in our study this would require 2,489 hours and 883 surveys, not logistically viable.