Design and Analysis of Line Transect Surveys for Primates

Abstract

Line transect surveys are widely used for estimating abundance of primate populations. The method relies on a small number of key assumptions, and if these are not met, substantial bias may occur. For a variety of reasons, primate surveys often do not follow what is generally considered to be best practice, either in survey design or in analysis. The design often comprises too few lines (sometimes just 1), subjectively placed or placed along trails, so lacks both randomization and adequate replication. Analysis often involves flawed or inefficient models, and often uses biased estimates of the locations of primate groups relative to the line. We outline the standard method, emphasizing the assumptions underlying the approach. We then consider options for when it is difficult or impossible to meet key assumptions. We explore the performance of these options by simulation, focusing particularly on the analysis of primate group sizes, where many of the variations in survey methods have been developed. We also discuss design issues, field methods, analysis, and potential alternative methodologies for when standard line transect sampling cannot deliver reliable abundance estimates.

Variable density responses of primate communities to hunting pressure in a western Amazonian river basin

“…Our research team followed line transect protocol as described in the literature specific to tropical forest surveys of primates (Peres, 1999a;Marshall et al, 2008;Buckland et al, 2010), with minor modifications to account for sitespecific circumstances. We implemented line transects of 1m width and varying length (from 750m to 1,500m, according to terrain conditions and station layout) at each site.…”

A Survey of mid and large bodied mammals in Núcleo Caraguatatuba, Serra do Mar State Park, Brazil

“…From the total of 71.9 trail km, the majority (51.9 km) were in forest dominated by early or advanced secondary successional stages, followed by primary (7.9 km) and eucalyptus and pine plantations (6.8 km). Standard line transect protocols (Peres 1999, Buckland et al 2010 were adapted to fit our main objective of sampling mid and large bodied mammals across the widest possible variety of habitats within the park. Census was not conducted during heavy rainfall but did occur during light showers i.e.…”

“…For example we did not detect any mammals before 9 AM. To enable us to survey the maximum range of habitats possible we did not follow the recommended line transect survey speed of ≈1.25 km per hour (Peres 1999, Buckland et al 2010). Although we did pause regularly at 100 to 300 m intervals to listen for detection cues, our mean per trail census speed was above the recommended value (survey speed: mean, range = 2.4, 1.1-3.4 km per hour).…”

Distribution, Abundance, and Spatial Ecology of the Critically Endangered Ecuadorian Capuchin (Cebus Albifrons Aequatorialis)

“…Parker and Carr [17] reported seeing four distinct social groups of capuchins ranging in size from 5-18 individuals, with a total population of 37 individuals. In our census 13 years later, the total population at Jauneche consisted of 33 individuals in two social groups ranging in size from [13][14][15][16][17][18][19][20]. These data suggest that the Jauneche population is approximately stable or decreasing slightly, with significant restructuring of the social groups.…”