dors within their home range or between foraging and nesting sites (Lovejoy
et al. 1986; Isaacs 1995; and see Bennett 1998 for review).
Migratory movements of wildlife through corridors have been observed in
mammals, birds, and amphibians (Newmark 1993; Powell and Bjork 1995;
Forman and Deblinger 2000). Wildlife species in these studies have been
observed preferentially moving through forested corridors rather than the sur-
rounding agricultural matrix. One study in Costa Rica, for example, showed
that large tropical frugivores (e.g., resplendent quetzal, Pharomachrus
mocinno) needed forested corridors from montane to lower elevational forests
so that birds could follow seasonal changes in their food supply (Powell and
Bjork 1995).
Dispersal movements normally are described as the one-way movements of
young animals seeking unoccupied territories in which to breed. Corridor
studies have demonstrated that the dispersal movements of mammals, birds,
butterflies, and plants can be assisted by habitat linkages (Bennett 1998). Dis-
persal movements are important for population dynamics because they allow
individuals to immigrate to new populations or to recolonize locally extinct
populations. One of the key challenges concerning the effectiveness of corri-
dors is to demonstrate that dispersing individuals not only move through cor-
ridors but also become established in fragment populations. Only in this way
can immigrants reduce the negative consequence of insularization on frag-
ment populations. Genetic evidence is beginning to accumulate that confirms
that gene flow is occurring between fragmented faunal populations linked by
corridors, thereby demonstrating the successful establishment of immigrants
in the population (Mech and Hallett 2001).
Providing Habitat for Resident Species
Depending on the shape, habitat structure, and floristic composition of corri-
dors, a range of wildlife species may reside in them. Edge and generalist species
probably are the most common occupants of corridors, predominating in nar-
row habitat strips that occur along roadsides, riparian areas, and windbreaks
(Crome et al. 1994; Hill 1995; Forman 1997; Laurance and Laurance 1999;
de Lima and Gascon 1999), although some forest species may also be present
(Harvey 2000). These types of corridors often are just slender strips of edge
habitat with little or no interior. Rare and endangered species usually avoid
such areas and are more likely to reside in wider corridors with a higher-qual-
ity (or interior) habitat (Laurance and Laurance 1999).
Residency in corridors is the most effective way of maintaining population
connectivity, particularly for less mobile species or those that will move long
distances (Bennett 1990). For such species, corridors must provide adequate
resources such as food and shelter. If habitat is suitable for residency, then pop-
ulation continuity (and gene flow) will be maintained by both the movements
- Landscape Connectivity and Biological Corridors 53