Intraspecific variations in home range overlaps of a semi-free range herbivore are explained by remotely sensed productivity

Abstract

In this study, we used remotely sensed Enhanced Vegetation Index (EVI) as a measure of food abundance to explain intraspecific home range overlap of Global Positioning System (GPS) collared semi-free range herbivores (Bos taurus). We then tested whether seasonality (estimated using the coefficient of variation of EVI) was related to intensity of home range overlap. We also tested whether the intensity of home range overlap was related to distance from water, particularly during the dry season. We determined the intensity of home range overlap using the Utilization Distribution Overlap Index. We then modelled the intensity of home range overlap as a function of seasonality. Results show that intensity of home range overlap varied with seasonality in a non-linear U-shaped manner. In addition, results showed that at both high and low levels of seasonality, intensity of home range overlap was high while it was low at moderate levels of seasonality. Results also indicated that the intensity of home range overlap increased with distance from water during the dry period. The U-shaped relationship obtained in this study conform to the behavioural theory that predicts similar relationships between food abundance and territoriality, indicating that remotely sensed productivity is an ecologically meaningful measure of food abundance. This further amplifies the utility of the combination of GPS animal movement data and remotely sensed data in spatial ecology.

Keywords:

• home range overlap
• GPS
• UDOI
• remote sensing
• GIS
• semi-free range

Acknowledgements

We thank Alexander Caron and Michel de Garine-Wichatitsky for their assistance in data collection. We are grateful to the Malipati farmers and the Department of Veterinary Service who allowed us to conduct this study in their area. This work was conducted within the framework of the Research Platform ‘Production and Conservation in Partnership’, RP-PCP. We thank the Ministère Français des Affaires Etrangères for the financial support through the French Embassy in Zimbabwe (RP-PCP grant/project CC#2). The project was also supported by the DAAD Zimbabwe in-country scholarship and University of Zimbabwe. We also thank the anonymous referees whose comments helped improve the manuscript.