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6. Hanya G, Yoshihiro S, Zamma K, Kubo R & Takahata
Y (2003) New method to census primate groups:
estimating group density of Japanese macaques
by point census. American Journal of Primatology 60: 43-56.
Abstract. We devised a new method to estimate the density of primate groups whose habitat is too steep to conduct a line transect census. 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: , whereas was a constant. , the detectability constant, was a constant when distance-dependent detectability g(y) was regressed on a half normal model: , 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 km2 was divided into twenty-eight 500 m~500 m grid squares. One observer was positioned at a point in each grid square, and those points were censused simultaneously for four-six days from 6:00-7:00 to 15:00-16:00. Four troops were followed for 144 hours during the point census. Distance-dependent detectability closely correlated with the half-normal model. Detectability constant varied with the time of day, but troop identity or topography did not influence it. Group density was calculated to be and groups/km2 in the disturbed and undisturbed areas, respectively (95% confidence limit). eTruef 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.
Key words: census method; point census; group density; half-normal model; Japanese macaque
<Written by: Goro Hanya (hanya<atmark>pri.kyoto-u.ac.jp)>
<Contact: Goro Hanya (hanya<atmark>pri.kyoto-u.ac.jp)>
<Last update: December 5, 2005>