Return to preferred habitats (edges) as a function of distance in Akodon azarae (Rodentia, Muridae) in cropfield-edge systems of central Argentina

Abstract

We studied the ability of Akodon azarae (Rodentia, Muridae) to return to their preferred habitat, when released at a perpendicular distance (25, 50 or 75 m) from the edge towards the cropfield, and a parallel distance (100 m) away from the site of first capture within the edge habitat. Return success was estimated as the proportion of animals recovered in edges. The recapture rate between the field and the border was significantly higher than the recapture rate estimated according to successive captures in the border. Successful returns did not decrease significantly with increasing release distance, but animals released at 50 m from edges were less successful in returning to borders than the other release-distance groups. Although the median time taken to the first recapture in edges did not differ among the release-distance groups, rodents released at 25 m and 50 m returned to edges faster than those released at 75 m. A. azarae showed both a successful return to the edge and a trend to return to the home range area. We conclude that A. azarae can return to edges from cropfields at distances that are larger than those they usually travel, allowing the use of fields when they present good conditions for reproduction and survival. Successful return is probably the result of direct movements rather than random wandering.

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

“…We assumed that rodents only use the crop field area located closer than 50 m to the border, so an increase in the size of the plots leads to a greater proportion of the crop field not used by rodents. The 50 m distance was chosen according to Hodara and Busch (2006). For these scenarios, we considered that increasing plot sizes were associated with declining rates of use by rodents (75 and 50%).…”

“…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.…”

Foraging efficiency of Akodon azarae under different plant cover and resource levels

“…The most frequent crops include wheat, maize, soybean and sunflower. Seasonal changes in plant phenology and in the stage of development of crops cause seasonal qualitative and quantitative variations in resources-both in cropfields and borders (Busch et al 1997;Hodara and Busch 2006). Resources for rodents are both less abundant and less available in the winter than in the other seasons, with variations largely due to changes in plant cover, plant species composition and availability of invertebrate prey .…”

“…In these systems, rodents are found in crop fields, pastures and longitudinal habitats, such as railway and crop field borders and river banks (Bonaventura et al 1988;Ellis et al 1997;Busch et al 2001). Edge habitats are less disturbed than agricultural fields, maintaining high plant cover throughout the year, thereby providing good habitat conditions for small rodent species (Hodara and Busch 2006). A. azarae shows a strong habitat selection for less disturbed habitats with high vegetal cover (Bonaventura et al 1988;Busch et al 2001;Hodara et al 2001), but it increases its use of fields when crops are mature and when crops and weeds are well developed (Bilenca and Kravetz 1998).…”

“…Most potential predators of rodents in the area are birds, while terrestrial predators are scarce (Bellocq 1988;Hodara and Busch 2006). In the study area, owls capture their prey preferentially along crop field borders, but predation is greater for other rodent species than for A. azarae, probably because of the competitive dominance of the latter species, which has access to safer sites (Bellocq 1987(Bellocq , 1988.…”