Habitat selection and interspecific competition in rodents in pampean agroecosystems

Abstract

We analyzed the effect of density-dependent habitat selection and interspecific competition on the use of space by small rodent species in agroecosystems. We studied rodent abundance in cropfields and their borders, weedy margins less disturbed by agricultural activities. We could distinguish two kind of species : those habitat intolerants, Akodon azarae and Oil· goryzomys flavescens, which select the borders, and those habitat tolerants, Calomys laucha and Calomys musculinus. The two most abundant species in the community, A. azarae and C. laucha, differ in their habitat use : while the first has a clear preference for borders, the other is more equally distributed between habitats, although it is more abundant in fields. Both species show a shift towards an increased use of fields via density-dependent habitat selection with increasing abundance at some moments of the year. C. musculinus does not show habitat preference in any season, overlaping with the other species in both habitats. There is an interspecific effect on habitat use between A. azarae and C. laucha: While the first species cause a shift in habitat preference of C. laucha towards fields, this latter species affects the density-dependent habitat use of A. azarae. It is concluded that the pattern of habitat use of the studied species is affected by their differential preferences as well as by intra and interspecific density-dependent processes that change seasonally.Resume. -Nous avons analyse Peffet de la selection de l'habitat densite-dependante, et de la competition interspecifique sur 1'utilisation de 1'espace par les especes de petits rongeurs qui vivent dans les agroecosystemes. Nous avons etudie l'abondance des rongeurs dans les champs cultives et leurs limites, des bordures couvertes d'herbe moins perturbees par les acti-vites agricoles. On distingue deux categories d'especes : celles qui ne tolerent pas de variation de leur habitat, Akodon azarae et Oligoryzomys flavescens qui choisissent les bordures, et celles qui sont tolerantes, Calomys laucha et Calomys musculinus. Les deux especes les plus importantes dans la communaute, A. azarae et C. laucha, different dans leur utilisation de l'habitat. La premiere a une nette preference pour les bordures, tandis que 1'autre est repartie plus egalement dans les differents habitats, bien qu'elle soit plus abondante dans les champs. Les deux especes manifestent une tendance ä un usage accru des champs par intermediate d'une selection de l'habitat densite -dependante, avec une abundance qui s'accroit ä certains moments de 1'annee. C. musculinus ne montre en aucune saison de preference d'habitat, se trouvant avec 1'autre espece dans les deux habitats. II y a un effet interspecifique sur ('utilisation de l'habitat entre A. azarae et C. laucha: tandis que la premiere espece cause un changement dans la preference d'habitat de C. laucha vers les champs, cette derniere espece affecte l'utilisation de l'habitat densite-dependante de A. azarae. On conclut que le schema d'utilisation de l'habitat par les espe...

Reproductive characteristics of free-livingCalomys venustus (Rodentia, Muridae)

“…This phenomenon has been observed in other sigmodontine species in the pampean region (Hodara et al 2000, Kravetz and de VillafaZe 1981, Mills et al 1992, Zuleta et al 1988). Busch et al (1997) and Cittadino et al (1994Cittadino et al ( , 1998 argue that there is more evidence that annual declination is caused by an interaction of climatic factors and habitat quality. Climatic factors may act directly or through their effects on the habitat quality, with intra-and inter--specific density effects, influence survival, dispersion and habitat selection.…”

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 .…”

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

“…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.…”