Factors Affecting Variability in the Distribution of Elephants at Nazinga Game Ranch (Burkina Faso, West Africa)

Seasonal ground total counts were used to estimate elephant (Loxodonta africaca africana) population parameters in Nazinga Game Ranch, Burkina Faso. Remote sensing and GIS technology were used, as well, to relate the species distribution to environmental and anthropogenic variables, which were Normalized Difference Vegetation Index, elevation, stream density, poaching density, distance to dams, distance to rivers, distance to roads, and distance to poaching events. Elephant density varied seasonally and locally. Overall dry season density (0.24 elephants/km2) was higher (P = 0.035) than overall wet season density (0.09 elephants/km2). Mixed groups accounted for 46% of sighted groups in the wet season versus 59% of sighted groups in the dry season. Groups of females and calves accounted for 27% and 8% of sightings in wet and dry seasons whereas male groups accounted for 27% and 33% of groups in wet and dry seasons, respectively. Overall mean group size during the wet season (8.09 ± 4.62) was not different (P = 0.48) from mean group size during the dry season (6.22 ± 1.56). High number of males in the population resulted in a slightly skewed adult male-female sex ratios of 1:2.1 in the wet season and 1:1.2 in the dry season. The elephant population had similar young to adult age ratios of 1:1.1 and 1:1.4, in wet and dry seasons respectively. Elephants occupied 161.29 km2 or 16.8% of the ranch area during the wet season and 173.3 km2 or 18% of the ranch area during the dry season. The overlap between seasonal range was 68.9 km2 or 7.2% of the ranch area. Elephants randomly used habitat during the wet season but selected for riparian forest during the dry season. Poaching density explained 81%, vegetation greenness 7%, and stream density 3% of the variation in elephant abundance. Elephant distribution represented a survival strategy that was affected by poaching, food quality and abundance, and water availability