“The Effect of Landscape Parameters on African Elephants (Loxodonta africana) Movement Decisions”
Introduced by Professor Maggi Kelly
Understanding how movement decisions of individual animals are related to their surrounding landscape can promote the conservation of the species and their habitat. Moreover, the effect of the animal’s internal state on its movement pattern has not been closely examined. In southern Africa, land use changes and fencing of reserves restrict the movement of African elephants (Loxodonta africana). Concentration of elephants in limited areas causes vegetation degradation and leads to increased human-wildlife conflict. I examine what is the relative importance of detailed landscape parameters in determining elephants’ movement direction and speed. GPS-GSM collars fitted on fifteen elephants in Etosha National Park, Namibia, collected location information every minute-20 minutes during three years. I used extensive field work, collected during both the dry and the wet season, together with time series analysis of MODIS vegetation indices, to measure detailed vegetation information in Etosha. I mapped the density, cover, biomass, productivity, and temporal variability of woody and herbaceous vegetation. Distances to roads, fences, and water sources were calculated. I used a step selection function to compare the relative importance of these landscape parameters in determining elephants’ directional movement. I further used logistic regression to understand the relationship between elephants’ movement speed and the habitat quality, as perceived by the individual. I examined the effect of individuals’ condition and the season on the relationship between movement patterns and landscape characteristics. My results show that elephants prefer to walk into areas with higher annual maximum and annual average productivity, but lower temporal variance of productivity. Further, I found that elephants stay closer to water resources and to roads, but away from the reserve borders. The temporal scale of analysis affects the results and shed further light on the mechanism of elephants’ movement decisions. Analysis of movement speed yielded similar conclusion about the elephants’ habitat preference, while providing further insight into why particular areas might be preferred. My methodology of combining detailed landscape maps, individual and temporal attributes, and analyzing the effect on both movement direction and speed, can be used to improve the understanding of how wildlife respond to natural and anthropogenic landscape features.
My dissertation is dedicated to the loving memory of my grandmother, Polina Rozin, who taught me to marvel at the wonders of nature.
I am deeply grateful to my advisors, Professors Wayne Getz and Maggi Kelly, for all the opportunities, support, and guidance they have provided me. I would not have been here without the loving support of my family and friends, in the Bay Area and in Israel, my labmates, and my colleagues in ESPM and in Etosha.