Effects of small barriers on habitat use by red deer: Implications for conservation practices

Artificial barriers such as wire fences constitute a common conservation management practice to protect vegetation from the browsing impact of large herbivores. Apart from protecting the fenced area, these barriers may affect the use of adjacent areas by animals. For example, they may interrupt major movement routes. We studied the effect of fences on an area used by red deer in Doñana National Park (Andalucía, south west Spain). We used an observational approach to study the effect of existing permanent barriers, and an experimental approach to investigate the effect of new barriers placed between the main areas through which animals moved from resting to foraging sites. Our study was carried out during the mating season, so we could also observe the effects on the distribution of females among harems. We found that “shadow areas”, where projection lines of the movement from resting to foraging areas were interrupted by the barrier, were used less by deer. In agreement with this result, grasses in shadow areas tended to be longer than in other areas, indicating unequal use of resources depending on the placement of barriers. Also, permanent barriers appeared to have negative, long-term effects on the maintenance of meadows as denoted by a higher proportion of rushes in meadows within shadow areas. Experimental barriers supported the cause-effect relationship by decreasing the number of deer using the experimental shadow areas. Our results demonstrated unexpected ecological effects of small barriers on the landscape, mediated by modification of the spatial behaviour of red deer.