Project Update: July 2005
Through the implementation of this proposal we have been obtaining knowledge of the densities of 22 large vertebrate species at the Caparú Biological Station area, Colombian Amazonia. This information will be used both to design a monitoring program for these species' populations and to support the local initative of designing a conservation area within the Yaigojé - Apaporis Indigenous Reserve, in which Caparú Station is located.
A linear transect training workshop was designed and conducted. Ten indigenous representatives participated during 3 days in various classroom and field activities explaining and putting into practice linear transect census techniques. Special emphasis was placed on standardizing the estimation of perpendicular distances amongst the team of surveyors as well as the walking speed along transects. The trained group has also had the opportunity to participate in one survey at Puré National Park, south of the study area.
With the help of three indigenous co-investigators, three large vertebrates surveys have been conducted at Caparú Biological Station (1°05 S, ´69°31´ W) and one north of the station at Pintadillo Creek (1°02´ S, 69°39´ W). Accumulated survey efforts total 1.152 km (Table 1). Population densities have been estimated for eight primate species: Alouatta seniculus; Cacajao melanocephalus,; Callicebus torquatus; Cebus albifrons; Cebus apella; Lagothrix lagothricha; Pithecia monachus; and Saimiri sciureus. Densities have also been estimated for more than 14 additional species, including: Tapirus terrestris; Mazama americana; M. gouazoubira; Crax spp.; Tinamus spp.; and Geochelone denticulata. Upon every sighting of a group or individual, the following information has been recorded: time; species; perpendicular distance to the first animal detected; group size; mean group spread; and location along the transect. Data have been analyzed using DISTANCE software. Given the limited number of observations for some species (e. g., Tapirus terrestris, Cacajao melanocephalus, Mazama spp.), data from both sites have been pooled in order to strengthen their site-specific density estimates. For those species with just a few detection events even when surveys are pooled (e. g., A. seniculus), density estimates (D) have been calculated by hand using the formula:
D = ND/L 2(ESW),
where D = group density (groups per square kilometer), ND = number of sightings for each species, L = cumulative transect length walked in each site, ESW = effective strip width, defined as the largest perpendicular distance observed for each species but excluding obvious outliers.
Surveys at Pintadillo Creek were not developed as initially proposed as a result of the very atypical low water level of the Apaporis River, and consequently the Pintadillo Creek, during the end of 2004 and the four first months of 2005. The survey site at Pintadillo is 6 km from the creek mouth in the Apaporis, and it could not be reached until late April to carry out the survey. Given this difficulty, only one of two initially proposed surveys at Pintadillo have been carried out. At Caparú, an additional survey was carried out in addition to the two initially proposed. In order to include two surveys at each site for analysis and comparisons, a survey that conducted at Pintadillo in 2002 will also be included.
Data collected at Pintadillo are currently being systematized. Final density estimates and analysis including data from both sites and different seasons are also being conducted.