Agricultural farming alters predator–prey interactions in nearby natural habitats

Abstract

Agricultural farming is a major consumer of global arable lands and has a direct effect on species decline through habitat destruction. However, agricultural endeavours can also evoke indirect threats that will result in behavioural modifications of indigenous species. In a desert ecosystem, where a political border led to a farming dichotomy between intensive cultivates in Israel and intact lands in Jordan, we compared the foraging behaviours and abundances of the red fox and two species of gerbils, close to and distant from farms, and during two moon phases. We estimated fox and gerbil foraging levels by track counts, and measured gerbil time allocation, vigilance and apprehension by the giving-up density method. While foxes were significantly more abundant and active at locations close to farms, gerbils were significantly more abundant and active at locations distant from farms. Moreover, the typical reduction in food consumption during full-moon nights was exhibited only at locations close to farms. These results could suggest that indicators of predation risk, such as illumination intensity or distance to cover, are not universal, and their effectiveness may depend indirectly on anthropogenic activities, such as agricultural farming. The results could also suggest that although intensive agricultural endeavours benefit foxes, they might increase the predatory pressure on gerbils in addition to the already known effects of habitat loss. Therefore, agriculture acts as a double-edged sword by reducing natural habitats, while at the same time changing the predator-prey natural balance.

Indirect interactions and conservation in human‐modified environments

“…Some species do not cope with the changed conditions and disappear, whereas others thrive on the elevated productivity of the new monocultures and become pests (Singleton et al, 1999). Such changes in species abundances will often be driven directly by the agricultural onslaught, but Shapira, Sultan & Shanas (2008) show that the indirect effects of agriculture on surviving species may be more pervasive than we have realized.…”

“…by increased levels of noise, lighting or movements on access roads), even though their near-farm sites were just 50-200 m from farms. Nonetheless, the effect of foxes is perhaps most plausible; the shifts in gerbil behaviour observed by Shapira et al (2008) are similar to those exhibited by several other species of rodents when exposed to increased risk of fox predation (Dickman, 1992;Kats & Dill, 1998). If this interpretation is correct, Shapira et al (2008) have uncovered a fine example of an indirect amensal interaction, in which humans negatively affect gerbils by improving conditions for the fox.…”

“…Nonetheless, the effect of foxes is perhaps most plausible; the shifts in gerbil behaviour observed by Shapira et al (2008) are similar to those exhibited by several other species of rodents when exposed to increased risk of fox predation (Dickman, 1992;Kats & Dill, 1998). If this interpretation is correct, Shapira et al (2008) have uncovered a fine example of an indirect amensal interaction, in which humans negatively affect gerbils by improving conditions for the fox. It is not clear whether the situation represents an interaction chain or an interaction modification (sensu Wootton, 1994), or both, but this could be resolved by further study.…”

“…In essence, Shapira et al (2008) found that two species of gerbils were less active at sites close to than distant from farms, and also foraged less efficiently near farms on moonlit nights. Ostensibly, these results are not surprising and reflect the expectation that habitat and other resources needed by gerbils are depleted by agricultural activity.…”

“…Shapira et al (2008) suggest that agricultural expansion may pose a particularly severe threat in arid environments as the transformation of land is extreme and the secondary and tertiary effects on native biota may be acute. However, their work also suggests that we might look for more such indirect interactions in other human-modified situations.…”