suffer higher mortality when dispersing across unsuitable habitat between patches
(Temple 1991).
3 The greater length of habitat edge allows incursions of predators from outside the
patch, increasing the predation rate on interior forest species. We discuss such a case
for birds in the eastern hardwoods of North America in Section 10.7 (Fig. 10.10b)
(Wilcove 1985; Temple and Carey 1988). Nesting success of ovenbirds (Seiurus auro-
capillus), red-eyed vireos (Vireo olivaceus), and wood thrushes (Hylocichla mustelina)
in these deciduous woodlands was reduced both by higher nest predation and
by increased brood parasitism from the brown-headed cowbird (Moluthrus ater)
(Donovan et al. 1995). In general, fragmentation results in the synergistic inter-
action of several deleterious factors, particularly habitat decay, reduced dispersal of
animal populations, and increased risk of predation (Hobbs 2001; Laurance and
Cochrane 2001). However, species respond differently to fragmentation of habitat.
Species that do not move far (insects, reptiles, some forest birds) are more restricted
than are highly mobile taxa (many birds, mammals, long-lived species, generalist preda-
tors) (Debinski and Holt 2000).
There follow examples where extinctions or steep declines were associated with a
change in habitat and where that change probably caused extinction.The Gull Island vole
The Gull Island vole (Microtus nesophilus) was discovered and described in 1889. It
was restricted to the 7 ha Gull Island off Long Island, New York. Fort Michie was
built there in 1897, its construction requiring that most of the island (and thus the
vole’s habitat) be coated with concrete. The species has not been seen since.The hispid hare
The hispid hare (Caprolagus hispidus) once ranged along the southern Himalayan
foothills from Nepal to Assam but is now restricted to a handful of wildlife sanctu-
aries and forest reserves in Assam, Bengal, and Nepal. This short-limbed rabbit-like
hare depends on tall dense grass formed as a successional stage maintained either by
monsoon flooding or by periodic burning (Bell et al. 1990). The hare’s decline reflects
fragmentation of suitable habitat by agricultural encroachment. Most of the surviv-
ing populations are now isolated in small pockets of suitable habitats in reserves.
Much of the natural grassland has been lost to agriculture, forestry, and flood con-
trol and irrigation schemes. What remains is modified, even within the reserves, by
unseasonal burning and grass cutting for thatching material.
Like many endangered species, especially those that are small or inconspicuous,
neither density nor rate of decline has been measured. The current status was deter-
mined from searches of the few remaining pockets of tall grassland. There is some
evidence that contraction of the species into pockets of favorable habitat renders indi-
vidual hares more vulnerable to predation.Wallabies and kangaroos
Some of the more dramatic examples of driven extinctions involve the ecology of a
significant segment of the fauna being disrupted by large-scale and abrupt habitat
changes. In Australia there has been a substantial depletion of the Macropodoidea
(about 50 species of kangaroos, wallabies, and rat-kangaroos) following European
settlement (Calaby and Grigg 1989).314 Chapter 18