ORIGINAL INVESTIGATION Use of space by Necromys lasiurus (Rodentia, Sigmodontinae) in a grassland among Atlantic Forest fragments Alexandra dos Santos Pires 1 , Fernando Antonio dos Santos Fernandez à , Barbara Regina Feliciano, Daniela de Freitas Laborato´rio de Ecologia e Conservac ¸a˜o de Populac ¸o˜es, Departamento de Ecologia, Universidade Federal do Rio de Janeiro, C.P. 68020, Ilha do Funda˜o, 21941-902 Rio de Janeiro, RJ, Brazil Received 27 September 2008; accepted 20 April 2009 Abstract The spatial patterns presented by the rodent Necromys lasiurus were studied through capture-mark-recapture in a grassland among Atlantic Coastal Forest fragments in Southeastern Brazil. Males moved farther than females. Males moved similar distances in the dry and wet seasons, whereas females moved significantly longer distances in the dry season. Home ranges sizes were estimated for 32 individuals, and varied from 0.02 to 0.52 ha. Males had larger home ranges than females when all data are pooled and in the wet season; in the dry season home ranges of both sexes were of similar sizes. Home range sizes did not vary significantly between seasons for either sex. Home ranges of males overlapped extensively among themselves and with females, whereas females showed mutually exclusive home ranges. The spatial patterns described here are consistent with the results found for this species in different habitats and they suggest that N. lasiurus has a promiscuous mating system. r 2009 Deutsche Gesellschaft fu ¨ rSa ¨ ugetierkunde. Published by Elsevier GmbH. All rights reserved. Keywords: Necromys lasiurus; Home range; Mating systems; Rodents; Territoriality Introduction The knowledge of an animal’s home range size, shape and pattern of utilization can provide valuable ecologi- cal information about population density, foraging behavior, habitat selection, distribution of resources, spacing of individuals and their interactions (Harris et al. 1990). Intraspecific variation in home ranges can be influenced by sex, population density, season, reproductive condition and distribution and abundance of food resources (Wolff 1985; Ostfeld et al. 1985; Attuquayefio et al. 1986; Swihart and Slade 1989; Bonaventura et al. 1992; Fernandez et al. 1996). In mammals, the greater parental investment by females – in order to maximize fitness through enhanced offspring survival – results in intersexual differences in spatial patterns (Emlen and Oring 1977; Ostfeld 1990). Additionally, as such differences are related to repro- ductive strategies, the knowledge of home range sizes, distribution and overlap can help understanding the mating system of a population (Gaulin and Fitzgerald 1988; Swihart and Slade 1989; Heinemann et al. 1995). Most studies on home ranges and other aspects of spatial patterns in rodent populations have been carried out in temperate regions; for neotropical rodents, however, spatial patterns remain poorly known despite some detailed studies based on trapping data (Stallings ARTICLE IN PRESS www.elsevier.de/mambio 1616-5047/$ - see front matter r 2009 Deutsche Gesellschaft fu ¨ rSa ¨ ugetierkunde. Published by Elsevier GmbH. All rights reserved. doi:10.1016/j.mambio.2009.04.002 Mamm. biol. 75 (2010) 270–276 à Corresponding author. Tel.: +55 21 22807943. E-mail address: rodentia@biologia.ufrj.br (F.A.S. Fernandez). 1 Present address: Departamento de Cie ˆ ncias Ambientais, Instituto de Florestas, Universidade Federal Rural do Rio de Janeiro, Brazil.