Small mammals in farmlands of Argentina: Responses to organic and conventional farming

Despite the important positive role that small mammals have in agricultural systems, mainly through their contribution to food webs, few studies have been conducted on the biodiversity and abundance of this group. Considering that Argentina is one of the most important agricultural regions of the world, our objective was to assess the effect of farming practices (organic vs. conventional) on species richness and abundance of small mammals in border habitats from agroecosystems of central Argentina. We predicted that the effects of farming practices on small mammal populations would vary with the degree of habitat specialization of species. We expected higher species richness and abundance of specialist species in border habitats of organic than on conventional farms. We found that farming practices did not explain species richness; the number of species in border habitats was low with small variation between managements. Management, season and vegetation volume explained abundance of both specialist and generalist species in border habitats, but with additive effects in the former and interactive effects in the latter. During summer, Calomys musculinus, Calomys laucha and Akodon azarae were more abundant in border habitats of organic than on conventional farms. This could be related to the highest reproductive activity of these species in this season, associated to the highest habitat quality of organic border habitats. Also, organic farms may have an important role for specialist species in poor-quality habitats at the beginning and at the end of the reproductive period (spring and autumn). Our results showed a positive trend in small mammal abundance of organic farms in farmlands under intensive agriculture. The differences between Argentinian and European agriculture systems are discussed.