The Hub Conservation Area - Montanans 4 Safe Wildlife Passage

that this impediment is deleterious to wildlifepopulations.Defining fragmentationMany fragmentation studies use the definitiondescribed by Fahrig (2003). This definition statesthat, “Habitat fragmentation is a process duringwhich a large expanse of habitat is transformedinto a number of smaller patches of smallertotal area, isolated from each other by a matrixof habitats unlike the original.” As Fahrig(2003) notes, this definition is not restrictedto habitat fragmentation. Rather, it describesan interweaving of habitat fragmentation andhabitat loss. Implicit in the definition are areduction in habitat, an increase in isolationof habitat patches, an increase in number ofpatches, and a decrease in size of patches.Proof of fragmentationeffects on wildlifeAlthough Fahrig (2003) suggests the need todefine habitat loss and habitat fragmentationas two distinct entities, since the mixing of thetwo lead to inconsistencies in research findings,most of the studies we encountered in ourliterature search did not make this distinction.Appendix 5 lists the fragmentation studieswe reviewed and identifies the positive ornegative effects of fragmentation on species’populations. Overall, the studies show thatfragmentation, when combined with habitatloss, has deleterious effects on populations. Itmust be noted, though, that the few studiesfocusing on fragmentation, in the absence ofhabitat loss, showed slight positive effects onsome wildlife populations. This was due to thelack of competition for resources in fragmentedhabitats and did not apply to wide rangingspecies.Fragmentation’s impacts on wildlifepopulationsThe studies we reviewed show that habitat lossand fragmentation are occurring throughoutNorth America, and are impeding the movementof wildlife populations (Merrill et al., 1994;Sawyer et al., 2005).The studies show that by preventing animalmovement, population viability decreases dueto an inability to disperse and ensure geneticvariability within subpopulations, leading to anincreased risk of species’ extinction (Pimm etal., 2006; Harris and Pimm, 2008; Vellend et al.,2006). The studies also show that fragmentationof the landscape can lead to predationchanges that could potentially decimate nativepopulations unable to move away from a newdanger (Crooks and Soule, 1999; Kinley andApps, 2001; Wittmer et al., 2005).Indirectly related to movement, fragmentationand habitat loss can lead to changes in individualmorphology (Neckel-Oliveira and Gascon, 2006;Lomolino and Perault, 2007; Fredrickson andHedrick, 2002; Schmidt and Jensen, 2005;Schmidt and Jensen, 2003). It has been suggestedthat the small body size of individuals noted insome fragmentation studies may be due to thelow quality habitat in fragmented habitat patchesand an inability for individuals to reach higherquality habitat in other patches. There alsoexists an increased risk of exotic species’ invasionon fragmented landscapes with the potentialelimination of native species (Saunders et al.,1991; Crooks and Soule, 1999). In a fragmentedlandscape, native species are less likely or unableto recolonize fragments within which populationshave been lost.The vast majority of the studies we reviewedwere fragmentation studies as defined above, inwhich fragmentation and habitat loss go handin-hand.We did encounter a few studies thatfocused on fragmentation alone. These studiesfound or hypothesized that fragmentationcould potentially produce positive effectson populations. One such study showed anincreased movement and interbreeding betweentropical tree frog populations (Phyllomedusatarsius) (Neckel-Oliveira and Gascon, 2006). Theincreased dispersal noted in this study may bedue to a high population density in fragmentedpatches and a need for young, fit individuals toseek out alternate food sources on patches with35