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To drink or not to drink? Elephant movement strategies as surface water availability declines in a semi-arid savanna

Valls Fox H., De Garine-Wichatitsky M., T Makuwe E., Chamaille-Jammes S.. 2015. In : Visconti P. (ed.), Game E. (ed.), Mathevet R. (ed.), Wilkerson M. (ed.). Proceedings of the 27th International Congress for Conservation Biology and 4th European Congress for Conservation Biology " Mission biodiversity: choosing new paths for conservation". Washington DC : Society for conservation biology, p. 721-721. International Congress for Conservation Biology. 27, 2015-08-02/2015-08-06, Montpellier (France).

Water provision for wildlife is a common practice in semi-arid savannas. Sometimes, the viability of populations in protected areas is increased by, or even depends on, this provision. In these cases the distribution in space of perennial water sources is likely crucial, but so far little is known about the water-driven movement strategies of animals: as water sources dwindle and forage depletion occurs, should individuals make long trips far away from water to obtain better foraging prospects or short trips close to water to guarantee drinking opportunities? This affects where animals will impact their environment. We analyzed GPS relocation data of elephant breeding herds during the 2013 dry season in Hwange National Park, Zimbabwe. Elephants prefer drinking at periodic time intervals every 24h, 48h and 72h. The average number of visits to water doubled from June to October due to the addition of short (about 4h) commuting trips between waterholes. As of September, 72h-trips disappeared, however the number of 48h-trips, reaching 5-8 km from water, remained constant. The number of 24h-trips increased and they were made at higher speed. As a result, during those trips, maximum distance to water increased from 2.5 to 4km, suggesting the avoidance of depleted foraging sites located close to water. Our study confirms that there is a threshold distance beyond which elephants cannot use the landscape during the dry season, but more importantly it reveals that below this distance elephants are able to adjust their use of the environment to foraging constraints.

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