Spatial relationships among members of a population of wall lizards.

Wall lizards occupied overlapping territories, the size of which seemed to vary directly with the dominance level of the individual. Average territories of both males and females encompassed about 25 square meters. The overlap in territories among males was about 8 percent, and among females, about 18 percent. When both sexes were considered, overlap was 100 percent. This spacing mechanism appeared to be effective in governing the number of resident males but less so in governing number of resident females.In each of three years, females outnumbered males by 3.5 to one, probably because, among non-resident individuals, males were forced to move about more than females in order to avoid resident males, and as a consequence were subjected to greater predation pressure. Of 47 lizards marked on the study area, 60 percent were resident; the remainder were apparently wandering in search of unoccupied habitat.The number of resident lizards increased over the 5-year period of study from 10 to 21 individuals. Over the same period the average snout-to-vent length of this population decreased from 70.7 mm to 68.2 mm among males and 63.2 mm to 57.3 mm among females, probably reflecting a younger age structure. Correlated with these changes in population size was an increase in predation pressure from feral cats as reflected in the incidence of caudal autotomy among lizards.