Temporal and spatial effects of food availability on rodents in agroecosystems

Abstract

Land use changes, particularly those involving agricultural expansion, affect rodent communities through alterations in habitat and resource availability. Changes in food availability differentially impact species, depending on their requirements and specialisations, and may influence the habitat distribution and population dynamic. In Argentina’s Pampean region, crop field borders provide favourable conditions for rodents, as they are less disturbed by agricultural activities than thecrop fields and maintain dense vegetation cover throughout the year, despite spatial and temporal variations in plant cover, height, and species composition, as well as in resource availability. These variations may be reflected in rodent abundance and reproductive activity. The goals of this study were to assess the availability of food resources for rodents in crop field borders: green biomass, seeds, and invertebrates at different seasons, and to assess the effect of food availability on rodentabundance and reproduction. We conducted capture-mark-recapture trappings at each site, and we estimated the availability of the main food items of rodents in 10 crop field borders. We employed Generalised Linear Mixed Models (GLMMs) to examine the variation of food availability along seasons and the effect of season and food availability on rodent abundance and reproduction. We found that biomass and seed availability were significantly lower in late autumn and late winter than in late spring and late summer. Invertebrate abundance was lowest in late autumn. Rodent abundance and reproduction varied seasonally. Food availability influenced rodent abundance and reproduction, especially for Oxymycterus rufus, the most specialised of the species studied. Our findings indicate that most variations in rodent abundance are explained by seasonal changes, which include variations in environmental factors, such as temperature and precipitation, and in food resources.