Is the matrix really inhospitable? Vole runway distribution in an experimentally fragmented landscape

Abstract

Cook, W. M., Anderson, R. M. and Schweiger, E. W. 2004. Is the matrix really inhospitable? Vole runway distribution in an experimentally fragmented landscape. -Oikos 104: 5 -14.Habitat fragmentation is a common feature of modern landscapes, with significant impacts on the population densities of and space use by animals. A frequent model system for studying these effects is that of voles (Microtus spp.) and other rodents in experimentally fragmented grasslands. Design of these study sites is motivated by landscape theory, and often assumes that the matrix between discrete experimental habitat patches is inhospitable to focal species. Our census of M. ochrogaster runways in an experimentally fragmented landscape in eastern Kansas indicates that voles make substantial use of the mowed matrix, and that such use increases with degree of habitat fragmentation. Census season (winter, summer) was also an important predictor of observed runway distributions. Our results suggest that voles may have home ranges that include multiple small fragments and also the intervening matrix, leading to overestimates of population density. While the assumption that the matrix is inhospitable in experimentally fragmented habitats may be justified in many cases, studies using the model system of Microtus spp. or ecologically similar rodents in grasslands should incorporate methods that account for use of the matrix.

Landscape matrix and species traits mediate responses of Neotropical resident birds to forest fragmentation in Jamaica

“…Four proximate mechanisms have been proposed to explain divergent species responses to forest fragmentation as a function of the composition and the configuration of matrix land cover: (1) differential impedance or facilitation of inter-patch movement (e.g., Renjifo 2001, Ricketts 2001, Gobeil and Villard 2002, Revilla et al 2004, Bender and Fahrig 2005; (2) differential alteration of interspecific interactions, in particular predation (Rodewald andYahner 2001, Chalfoun et al 2002); and differential mediation of resources either (3) by habitat compensation via the addition of alternative or supplemental resources (e.g., food or nesting sites) in certain matrix areas (e.g., Gascon et al 1999, Norton et al 2000, Brotons et al 2003, Cook et al 2004 by the disparate reduction of within-patch habitat quality (i.e., microclimate and vegetation structure) due to dissimilar edge effects (Saunders et al 1991, Ries et al 2004 or different human disturbances (Friesen et al 1995, Rodewald andBakermans 2006). Collectively, our results are consistent with the hypothesis that resource availability may be the important driver of bird community changes in Jamaica's fragmented landscapes.…”

“…In many cases, matrix habitats may be hospitable for native species and may provide supplemental or additional resources that allow for population maintenance or growth in fragmented systems (Norton et al 2000, Brotons et al 2003, Cook et al 2004. In comparison to bauxite lands, peri-urban and agricultural matrices contained greater vegetation cover and complexity (Appendix B).…”

“…The landscape matrix, however, can mediate processes that influence speciesarea and isolation relationships other than dispersal (Ewers andDidham 2006, Kupfer et al 2006). First, different matrix types may provide alternative or supplemental resources (e.g., food or nest sites) that support greater species abundances than would be expected based on amounts or quality of primary habitat alone (i.e., habitat compensation hypothesis) (e.g., Gascon et al 1999, Norton et al 2000, Brotons et al 2003, Luck and Daily 2003, Cook et al 2004. Second, the type and extent of contrast between matrix habitats and forest remnants can also mediate the magnitude of edge effects, such as nest predation and parasitism (Donovan et al 1997, Chalfoun et al 2002, Driscoll and Donovan 2004, or the alteration of withinpatch conditions (e.g., vegetation structure, microclimate) (Saunders et al 1991, Ries et al 2004) (i.e., edge effects hypothesis).…”

Animal transportation networks

“…Most species of Microtus voles, for example, actively construct above ground 'runway' systems, which they clear by cutting vegetation [62]. Social caterpillars leave both pheromone and silk threads which are followed by other caterpillars [63], and which collectively create a foraging network used to connect the caterpillars' nest to food sources [64].…”

“…There are, however, some reports of individuals 'free loading' by exploiting the established transportation networks of others. Several species of small mammal, for example, use the runway systems constructed by voles [4,70] though they do not contribute to network clearing or maintenance [62].…”