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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). ‘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.
Key words: census method; point census; group density;
half-normal model; Japanese macaque
<Written by: Goro Hanya (hanya.goro.5z<atmark>kyoto-u.ac.jp)>
<Contact: Goro Hanya (hanya.goro.5z<atmark>kyoto-u.ac.jp)>
<Last update: December 5, 2005>