Aim Dispersal is a critical component of animal ecology that is poorly understood for most species. In particular, savanna elephants (Loxodonta africana) have been studied for decades in national parks across Africa, but little is known about their dispersal into new or unused habitats or their population dynamics in human-dominated landscapes. We capitalized on a natural dispersal event of savanna elephants recolonizing communal land in southern Kenya to document their demographic characteristics and genetic relationships.
Location Rift Valley province of Kenya.
Methods We collected faecal samples and used genetic methods to identify individuals, estimate the sex ratio and evaluate the patterns of relatedness within the female groups and male aggregations. We also measured dung bolus circumference to assign age classes to individuals and estimate the age structure.
Results We identified 112 individuals with a sex ratio not different from one (1.32:1.00). The age structure was skewed towards younger elephants (71%), suggesting the potential for rapid growth from reproduction. We detected significantly higher kinship levels within female groups (R = 0.124 ± 0.023), suggesting that family groups colonized the site, but found little support for higher-order genetic relationships among female groups. Males detected together were unrelated (R = 0.003 ± 0.030).
Main conclusions Our results suggest that highly social mammals, such as savanna elephants, disperse into unoccupied habitat as family groups and that a young demographic structure and a large number of males might be expected in establishing populations. These findings highlight the potential value of indirect, non-invasive methods for assessing elephant herd and demographic characteristics when direct observations are difficult.