Movement Patterns and Density of Varanus albigularis

-A population of white-throated savanna monitor lizards (Varanus albigularis) in Etosha National Park, Namibia, was studied for 17 months. A total of 238 lizards was examined, of which 31 were radiotagged for periods up to 14 months. The hot/wet season (January-April) home ranges determined from radiotelemetry data were large and differed significantly between adult males (18.3 + 2.4 km2) and females (6.1 + 0.6 km2). During the cool/dry season (May-August) males and females utilized less than 10% of their wet season home range, except during the mating period (July-August), when males moved extensively while locating estrous females. When supplemental food was made available during the cool/ dry season, male lizards increased their daily movements over 30-fold, suggesting that food, not seasonal differences in ambient temperature, limits activity. The largest adult lizards were males; however, there was no difference in wet season mass between males and females of similar snout-vent length. The apparent sex ratio varied dramatically by season, but this was a result of the different activity patterns between the sexes. Overall, the data suggest parity between the sexes. The biomass of V. albigularis at least rivaled that of any sympatric medium and large-sized mammalian carnivore species in the park. Estimates of the biomass of lizard populations have concentrated on species that are physically small (e.g., Bennett and Gorman, 1979; Dunham, 1982; Ruby and Dunham, 1984; Pilorge, 1987; Barbault and Mou, 1988). Biomass estimates for populations of large lizards are far less common; however, several studies concerned with population estimates of large herbivorous lizards (Sauromalus, Cyclura) suggested that their density is often comparable to that of 407 This content downloaded from 157.55.39.124 on Sat, 23 Jul 2016 05:23:35 UTC All use subject to http://about.jstor.org/terms