Line Transect Estimates of Ungulate Populations in a Mediterranean Forest

Abstract

We used line transect (distance) methodology to estimate the population density of fallow deer (Dama dama), roe deer (Capreolus capreolus), and wild boars (Sus scrofa) in a dense Mediterranean forest. Three different surveys ( 1 per year from 1995 to 1997) were analyzed. Density estimates, pooled among years, for fallow deer (9.9 deer/km 2 , %CV = 24) and roe deer (8.5 deer/km 2 , %CV = 21) were more precise than the estimate for wild boars (10.6 boars/km 2 , %CV = 55). Fallow deer density was significantly higher during 1997 than during 1995 or 1996. For wild boars, we found differences among years (1995: 23.6 boars/km 2 , %CV = 23; 1996: 10.9 boars/km 2 , %CV = 24; 1997: 3.9 boars/km 2 , %CV = 33). We attempted a confirmatory analysis using an independent survey method for fallow deer and total counts at supplementary feeding sites for wild boars. These comparisons showed that line transect estimates were negatively biased for fallow deer during 1996-1997 and for wild boars during 1997. For adults, the composition by sex from line transects was compared with information collected from fixed observation points. Differences in sex composition for fallow deer and wild boars were found when these 2 methods were compared. The structure of the roe deer population was similar when line transect information was compared with independent survey data. A spike in the detection probability function for wild boars may have been caused by the difficulty of detecting boars >20 m from the transect. The careful use of line transect sampling may prove useful for both research and management of fallow deer, roe deer, and wild boars.