Structure et dynamique d’un peuplement de Lézards : les Scincides de la savane de Lamto (Côte-d'Ivoire)

Abstract

Population densities of terrestrial lizards were estimated monthly, for five consecutive years, in the Lamto savanna (Ivory Coast), by collecting all individuals within 900 m2 quadrats. Although their breeding cycles were different, the three most numerous species Mabuya buettneri, M. maculilabris and Panaspis nimbaensis were more abundant during the wet season. These skinks require six months to reach a mature size ; their daily rate of growth is about 0.2 to 0.3 mm. The average reproductive potential of females of Mabuya buettneri, M. maculilabris and Panaspis nimbaensis were determined by counting yolked ovarian follicles and eggs in oviducts, and by estimating clutch size. The average annual egg production was 13.4, 30.4 and 12.8 eggs in the above three species, and the number of clutches 1.5, 5.5 and 5.0 per female per year. Mortality of eggs and hatchings is high and survivorship to maturity is low : 18.2 %, 8,5 % and 25.1 % of eggs laid respectively by Mabuya buettneri, M. maculilabris and Panaspis nimbaensis. From sexual maturity onwards, the death rate for females is lower than that of males in all species, but is fairly high for both sexes. The longest average life expectancy is about 9.0 months for females of Mabuya maculilabris, and the shortest 1.3 months for males of M. buettneri. Although they are opportunistic feeders, these sympatric lizards do not compete for the same preys because their activity patterns, their behaviours and their sizes are fairly different. The annual food consumption of the ground lizard community in Lamto savanna is about 3 kg/ha (live weight) and its average net production, calculated from life tables, is about 300 g/ha/year. Ecological efficiency of the Mabuya species is 10 %.