Elephant Fences Result in Limited Impacts on Movement of Non-Target Species

Abstract

Mega-herbivore or elephant fences aim to prevent target animals (here: African savanna elephant Loxodonta africana, giraffe Giraffa giraffa) from crossing while allowing others, often with the intention to protect an area against elephants—for conservation, economic or research purposes. However, little is known about mega-herbivore fence effectiveness and impact on non-target species, for example impact on meso-herbivore movement, or fence avoidance. We hypothesised that mega-herbivore fences are effective in excluding mega-herbivores, whereas other species remain unaffected. We tested this hypothesis by comparing mammalian species abundance in (i) full exclosures, (ii) mega-herbivore exclosures and (iii) open plots. These plots were part of the Lapalala Elephant Landscape Experiment (LELE) project in Lapalala Wilderness, South Africa. Systematic dung pile recording and animal track counts—supported with video footage from camera traps—were used to quantify species-specific animal abundance using generalised linear mixed-effect models. The dung piles showed no difference in the abundance of non-target species between mega-herbivore exclosures and open plots, while target species were successfully excluded. Interestingly, we found fewer tracks of large non-target herbivores, such as plains zebra (Equus quagga) and greater kudu (Tragelaphus strepsiceros) crossing mega-herbivore fences compared to open plots, indicating that some individuals avoided crossing the mega-herbivore fence lines. We suggest that this avoidance is due to a combination of species-specific vigilance and deterrence of large specimens. Further research is needed to determine whether this avoidance persists over time, and if the absence of large non-target animals affects ecosystem functioning. Mega-herbivore fences are an effective means to prevent the movement of target species. However, some individuals of non-target species also avoid crossing these fences, likely large animals due to the minimum height of the fence. We recommend monitoring the movement of species once elephant fences are erected, and to increase minimum fence height if non-target species are affected.