population. Dispersal may result from density-dependent factors such as
limited resources (food, shelter, mates) or density-independent factors such
as inbreeding avoidance (not breeding with closely related individuals;
Howard 1960). Individuals can increase their chances of being accepted in
a new population by becoming receptive to breeding upon their arrival
(Lidicker 1975).
How capable a species is of moving through a corridor may depend on its
food and area needs, vagility, denning needs, social behavior, and other factors.
Bennett (1990) identified three types of species-specific movement along cor-
ridors. First, movement can be a single motion along the entire length of the
corridor, which could be seasonal in nature. This type of movement usually is
made by large, highly mobile species. For example, Grimshaw and Foley
(1991 in Newmark 1993) found that forest elephants on Mount Kilimanjaro
in East Africa made seasonal use of the remaining forest link between the
mountain and Amboseli National Park.
Second, corridor movement may be punctuated by pauses for food or shel-
ter that may last from hours to days or even weeks. This situation may be typ-
ical of smaller species that have high energy needs and limited mobility.
Finally, individuals may reside in a corridor, resulting in immigration and gene
flow through the resident population. Recent studies have demonstrated that
many species reside in corridors, including sensitive wildlife such as rainforest
birds and arboreal marsupials (Isaacs 1995; Laurance and Laurance 1999).
Many of the corridor features that facilitate animal movement across the
landscape also are beneficial to plant pollination and dispersal (Lamont and
Southall 1982; Chapter 12, this volume). The movement of plant pollen,
seeds, spores, and other propagules can occur via vectors such as wind, water,
and flying and terrestrial animals. Although plant pollination and dispersal
in habitat corridors have received little attention (Forman 1997; Lamont
and Southall 1982; Loney and Hobbs 1991), two movement patterns have
been detected. First, short-distance movements of some plant species have been
observed via vegetative spread or adjacent seed dispersal. Second, the most
common movements have been wind or animal dispersal of seeds some dis-
tance along the corridor (Hascova 1992). Plants that need wind pollination
and dispersal probably will not be as sensitive to corridor features such as habi-
tat quality and structure as plant species that clearly depend on an animal’s
ability to move through the landscape. The successful establishment of plants,
irrespective of their dispersal mechanism, into an appropriate environment
and their subsequent reproduction allows species to spread further across the
landscape (Forman 1997).
In addition to the types of species-specific movements there are four major
physical corridor features that will influence species use and movement in a
corridor. These are habitat quality, corridor width, length, and continuity.
56 I. Conservation Biology and Landscape Ecology in the Tropics