Long‐term variations in rodent abundance in a rural landscape of the Pampas, Argentina

Abstract

The goal of this study was to analyze the variations in abundance of rodent communities over the last 24 years in a rural area, and their relation to possible changes in climatic variables and land use. The principal change in the area observed along the study period was an increase in the area covered by soybean. The habitats studied were crop fields and borders. The total abundance of rodents did not show a significant trend of variation over time in crop fields while in borders the abundance in autumn-winter (A-W) showed a significant trend to decrease over time. The different rodent species showed a differential response over time. While Calomys laucha and C. musculinus showed a decrease between the period before and after the soybean expansion, Akodon azarae did not change its abundance over time. The mean minimum temperature increased over time while the number of days with frost decreased. Total rodent abundance in A-W was positively associated with the cumulated precipitation of the previous spring-summer period and negatively with the cumulated precipitation of the same period. We conclude that rodent abundance variations in crop fields and borders of the study area are influenced by precipitation, but the observed trends of variation over time are better explained by changes in agricultural practices than by meteorological variables.

Role of Landscape Scale in the Distribution of Rodents in an Agroecosystem of Argentina

“…The increase in size of agricultural plots is an increasing trend in the area, and in many cases internal fences are removed, along with the weed community. Previous results have shown a negative relation between the abundance of C. musculinus and C. laucha and field size (Adduci, Bustos, Gorosito, Fraschina, & Busch, 2012), and the effect of increased plot size has been proposed as an explanation of the decrease in C. laucha abundance between 1984 and 2008, along with the increase in soybean and no tillage methods (Fraschina, 2011).…”

“…The expansion of agriculture has caused an increase in abundance at a landscape scale of both species of Calomys with respect to A. azarae, because the population cycle of Calomys is highly synchronized with the phenology of maize, and the rotation of summer and winter crops favors the increase in these rodent populations (Kravetz & De Villafañe, 1981). During the last decades, however, the increase in soybean culture has caused a reversal of this trend (Fraschina et al, 2012).…”

“…The rodent community in the Pampean region has been widely described (Busch & Kravetz, 1992a, 1992bBusch, Alvarez, Cittadino, & Kravetz, 1997;Dadon, & Hodara, 2000;Busch et al, 2001;Hodara, Busch, Kittlen, & Kravetz, 2001;Hodara & Busch, 2006;Busch & Hodara, 2010;Fraschina, León, & Busch, 2012;León, Fraschina, Guidobono, & Busch, 2013), but mainly in crop fields, their borders, and poultry farms. Other habitats that support species with more specific requirements, such as railway embankments, woodlots and riparian habitats, have been poorly sampled.…”

The ecological value of long-term studies of birds and mammals in Central America, South America and Antarctica

“…Live-trapping conducted over 24 years (1984-2008) revealed that the transformation of native habitat to agricultural habitat had dramatic but species-specific effects on the native rodents in the community. Interannual fluctuation in the abundance of Azara's grass mouse (Akodon azarae), the dominant competitor in the rodent community, was attributed more strongly to variation in precipitation than changes in the physical habitat [87]. In comparison, the yellow pygmy rice rat (Oligoryzomys flavescens) numbers decreased within the converted agricultural areas, but increased in crop field borders.…”

“…Since the 1970's, agricultural practices have altered the habitats in the Rolling Pampas region of Argentina (34 o 08'S, 59 o 14'W), where much of the original vegetation and food resources consumed by rodent communities have been replaced with soy and agricultural crops [87]. Live-trapping conducted over 24 years (1984-2008) revealed that the transformation of native habitat to agricultural habitat had dramatic but species-specific effects on the native rodents in the community.…”