Where ) 0(h denoted the slope of the probability density function of detection distances evaluated at zero distance. Thus density estimates were obtained from estimates of ) 0(h and encounter rate (n/K), ρ is referred to as the effective radius and corresponds to the radial distance from the point transect within which the number of undetected groups was equal to the number of groups detected beyond the circle with that radius. The circular area of detection out to the effective radial distance gives the effective area of detection ν.