Guatemala harbors three species of primates (Alouatta palliates, Alouatta pigra and Ateles geoffroyi), but the distribution and state of conservation of populations of these species are poorly documented. In the case of A. pigra, populations have been studied recently and documented in several sites in Mexico and Belize, and only in one site in Guatemala (Tikal National Park). In this study, we report first-time population data for A. pigra existing in the Lachua Eco-region in northwestern Guatemala. Surveys were conducted between September 2002 and April 2003 in the northern portion (32 km(2)) of the Lachua National Park (LLNP
145 km(2)) and in a fragmented landscape north of the protected area. In this latter area we surveyed a large forest fragment (17.14km(2)), "Nueve Cerros", and 26 small forest fragments that ranged in size from 0.01 to 3.9 km2. Surveys resulted in a total count of 414 howler monkeys of which 403 belonged to 80 mixed-sex groups, four were solitary males, two were solitary females and five were found in two male groups. Standardized sampling effort among sites indicated 16.7 monkeys/100 survey hours at LLNP, 35.8 individuals/100 survey hours at "Nueve Cerros" and 71.0 +/- 62.2 individuals/100 survey hours in the forest fragments. Mean group size varied from 4.07 individuals at LLNP to 5.19 individuals in the forest fragments. Conservation problems for the black howler population surveyed are discussed, along with possible conservation scenarios.
