Variations in rodent’s communities over the last 24 years in Exaltación de la Cruz, Argentina.

FRASCHINA J; FERNÁNDEZ MARÍA SOLEDAD; BUSCH M

Mendoza, Argentina

Congreso; 10 th International Mammalogical Congress.; 2009

The aim of the present study was to analyze abundance variations in rodent communities along the last 24 years in a rural area, and to assess the effect of environmental variables and land use changes on these variations. In order to assess these changes we analyzed capture data of both cropfields and their borders at two moments of the cycle of rodent abundance, high abundance in Autumn-Winter and low abundance in Spring-Summer. We analyzed the temporal trend in abundance by simple linear regressions between rodent abundance and years (1984 - 2008), and we conducted multiple linear regressions between rodent abundance and climatic variables (minimum and maximum temperature, cumulated precipitation in autumn-winter and spring-summer and number of days with frost). Although overall rodent abundance decreased over time in cropfields and their borders, this variation was not significant in all seasons and species. While Akodon azarae (the most abundant species) did not show significative changes, Calomys laucha and C. musculinus abundance in autumn-winter decreased in both habitats and Oligoryzomys flavescens showed a decrease in the two seasons in cropfields, but an increase in borders in spring-summer. Total abundance of rodents in autumn-winter was positively associated to the cumulated precipitation of the previous spring summer period and negatively with the cumulated precipitation of the same period. To analyze the effect of the increase in soybean culture and the no- tillage technology on rodent communities we compared rodent abundances between the periods 1979-1997 and 1998-2008. C. laucha abundance is lower in the period 1998-2008 in borders, while C. musculinus abundance is higher in autumn-winter of 1979-1997 than in autumn-winter of 1998-2008 and spring-summer of both periods. The observed trends in rodent abundances are better explained by changes in land use than by climatic variables, whose changes are not associated with those observed in rodents.