The influence of electric fences on large mammal movements in the Kilombero Valley, Tanzania

Published source details Bonnington C., Grainger M., Dangerfield S. & Fanning E. (2009) The influence of electric fences on large mammal movements in the Kilombero Valley, Tanzania. African Journal of Ecology, 48, 280-284.
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Summary

Two types of electric wire fences were erected around a number of teak Tectona grandis plantations to prevent tree damage by African elephant Loxodonta africana in Southern Tanzania (8°34’S, 8°36’E). This study investigated the impact that these fences (one a eight-wire electrified ‘full’ 2 m high fence with the lowest wire approximately 50 cm above the ground, and the other a ‘half’ fence with a single electrified wire 1.5 m above the ground) have on large mammal movements in the area.

Six full fences and 16 half fences were surveyed in April and May 2005 and January and February 2006. Transects were walked along each of the fence types and spoor of all large mammals recorded. The spoor was categorised depending on the mammal’s movement near the fence. It was either recorded as ‘restrictive’ (if the mammal spoor did not cross the fence) or ‘accessible’ (if the mammal spoor passed across the fence). Mammal species were categorised depending on their shoulder height for the purpose of analysis.

As intended, both types of fencing created an impenetrable barrier towards elephants. Mammals < 2.5 m shoulder height were significantly more likely to penetrate the half fence compared to the full fence. All other ‘large mammal’ species recorded during the survey (species 1.5-2.5 m shoulder height, e.g. African buffalo Syncerus caffer and hippopotamus Hippopotamus amphibius passed through the half fence. A number of smaller species (0.5-1.5 m shoulder height, e.g. spotted hyena Crocuta crocuta and warthog Phacochoerus africanus did not penetrate the full fence on any occasion. These results have major implications for wildlife connectivity. Full fences prevented access of elephant into teak stands but were not selective in their nature thus all other ‘non-pest’ species were also prevented entry. On the other hand, the half fence was selective in the way it restricted elephant access but allowed other species entry and thus maintained habitat connectivity for these species. As a result of these findings, erection of half fences as an alternative to full fences is now the preferred conservation management strategy.

Note: If using or referring to this published study, please read and quote the original paper which can be viewed at: http://onlinelibrary.wiley.com/doi/10.1111/j.1365-2028.2009.01092.x/abstract