New method to census primate groups: Estimating group density of Japanese macaques by point census

Abstract

We devised a new method to estimate the density of primate groups in habitats that preclude the use of a line-transect census because the ground is too steep. We combined point census and group follows. From the number of groups counted at a fixed point for an hour, n, group density D was calculated: D = lambda n / pi. Lambda, the detectability constant, was a constant when distance-dependent detectability g(y) was regressed on a half-normal model: g(y) = e (-lambda y(2)) and can be estimated by combining the information of group follow and point census. Using this method, we estimated the group density of Japanese macaques in Yakushima. A census area of 7 km(2) was divided into 28 grid squares (500 m x 500 m). One observer was positioned at a point in each grid square, and those points were censused simultaneously for 4-6 days from 0600-0700 to 1500-1600 hr. Four troops were followed for 144 hr during the point census. Distance-dependent detectability closely correlated with the half-normal model. The detectability constant varied with the time of day, but it was not influenced by troop identity or topography. Group density was calculated to be 1.48 +/- 0.61 and 0.701 +/- 0.432 groups/km(2) in the disturbed and undisturbed areas, respectively (95% confidence limit). "True" group density estimated by home range data was within the confidence limit calculated by a point census in the home range of the troops for two troops, suggesting that this method was valid. This method is applicable to other species as long as at least one group can be followed, because it satisfies the fundamental assumptions of point census, and the detectability does not seem to be biased by troop or topography.

Spatial variation in density and total size estimates in fragmented primate populations: the golden‐crowned sifaka (Propithecus tattersalli)

“…Lastly, another factor that may explain their low density estimates is that the golden-crowned sifakas may not be easily seen from the hills where the observers are located because the sifakas often stay on the lower branches of the trees, at least during the dry season, when all the surveys were conducted, and when they were more easily detected from the ground [Personal Observation, 2006, 2008. This suggests that the methods used by Vargas et al [2002], widely used for songbird surveys, could be adapted for rapid census targeting initial conservation needs assessment, but the line-transects method may be more appropriate for more accurate primates census [see Hanya et al, 2003 for a counter-example]. We are confident that our estimates are not major overestimates since we found similar values in 2006 and 2008 for Bekaraoka, whoever was involved in the transect survey (EQ and local guides in 2006, AB, LC, JC, ER, and local guides in 2008).…”

Population Density and Abundance of Ebony Leaf Monkeys (Trachypithecus auratus) in West Bali National Park, Indonesia

“…Providing accurate descriptions of this species' status and demographic trends, long-term inventory studies are crucial for the decisions of wildlife managers in ways of preventing such population abundance estimates may also allow the comparison of our results with those obtained from alternative census methods, such as complete count surveys or methods combining point census and group follows (Harcourt and Fossey 1981;McNeilage et al 2001;Hanya et al 2003).…”

Comparisons of food availability and group density of Japanese macaques in primary, naturally regenerated, and plantation forests

“…1). The size of the census area was 10.7 times as large as the average home ranges of the four troops in the study site (0.70 km 2 [Hanya et al, 2003b]). One observer was positioned in each grid square at a fixed point.…”

“…We censused the Japanese macaques in August 2000August , 2001August , 2002August , and 2003 using point census and group follows [Hanya et al, 2003b]. All of the point observers were inexperienced, and they were trained for 1 day preceding the census.…”

“…All of the point observers were inexperienced, and they were trained for 1 day preceding the census. However, these inexperienced observers could reliably estimate group density [Hanya et al, 2003b]. We set a 7.5 km 2 census area and divided it into 30 grid squares (500 m  500 m; Fig.…”