The Hub Conservation Area - Montanans 4 Safe Wildlife Passage

example, if a grizzly bear had a home range of93 square kilometers, it does not necessarilymean that it is essential to conserve 186 squarekilometers of habitat for two grizzly bears,as there is some overlap of home range thatis tolerated within the species. Rather, it isimportant to determine the territory, or theamount of land within the home range, that thegrizzly bear will defend against another grizzlybear. This will provide the minimum amount ofland necessary for two grizzly bears to subsistand coexist in the same general area.MigrationThose animals unable to meet their basicsurvival needs in a single location may traverselong distances to do so. Migration is a seasonal,roundtrip, intra-population movement madeprimarily by resident adults between discreteareas not used at other times of the year(Semlitsch, 2007; Berger 2004). Migrationserves a variety of critical purposes, whichvary by species, subpopulation, year andlocation. Some animals migrate for parturition(birthing) purposes. This occurs when the landupon which a population subsists for much ofthe year is in some way inadequate for raisingyoung (i.e. predation risk for young is high),and, in turn, the land on which the young areborn does not provide adequate sustenanceyear-round (Semlitsch, 2007; Bergerud et al.,1990). Wildlife may migrate strictly based uponseasonal availability of food in different locales.This is seen when the summer range does notprovide nourishment for winter survival or viceversa,and is illustrated by migrations of somepronghorn (White et al., 2007; Sawyer et al.,2005), and mule deer (Sawyer et al., 2005;Brown 1992, Thomas and Irby, 1991).Still other wildlife species migrate based upona critical threshold at which point there is apotential for resource depletion. Migration ofsome individuals or an entire population may beseen when a population outgrows an area and itsresources. These are often referred to as partialor adaptive migrations (Alerstam et al., 2003).These migrations have been identified in the U.S.Northern Rockies in populations of pronghorn34(White et al., 2007) and elk (Boyce, 1991;Hebblewhite et al., 2006).Current migratory patterns of animals in theU.S. Northern Rocky Mountain region havechanged due to four main causes (Berger, 2004):1. Intolerance to bison outsideYellowstone National Park;2. Winter feeding of elk;3. Increased human population;4. Habitat loss.DispersalDispersal is an interpopulation, unidirectionalmovement from natal sites with no predictablereturns (Semlitsch, 2007; Sutherland et al.,2000). Dispersal determines population spread,allows for colonization and recolonization offragmented landscapes and encourages geneticflow (Trakhtenbrot et al., 2005; Hoffmanet al., 2006). Dispersal is less a matter ofimmediate individual or species survival, butrather a critical means by which a speciesmaintains long-term survival (Hoehn et al.,2007; Brown and Kodric-Brown, 1977). In fact,dispersing animals are less likely to survivethan their counterparts remaining in familiarterritory. Dispersing individuals are at a higherrisk of encountering human development androads, new predators, and low quality food intheir travels. Dispersal may prove ever moreimportant with increased fragmentation as ameans to maintain population viability throughgenetic flow.HABITAT FRAGMENTATIONResearch has indicated that the ability tomove across the landscape is necessary forlong-term population survival of species.Habitat fragmentation is thought to seriouslyimpair animal movement across the regionallandscape. Social and cultural pressures demandthat conservation and resource managementgroups bear the burden of proof thatfragmentation is occurring (due to both naturaland anthropogenic factors), that it impedesanimal movement across the landscape, and