Rodent Societies: An Ecological & Evolutionary Perspective

itate movement of predators, parasites, and disease organ-

isms across the landscape (Hess 1994; Watson 1991). A

more subtle effect is that corridors, like matrix, may act as

dispersal sinks. Individuals might be attracted to use corri-

dors as residences, but then fail to reproduce enough to re-

place themselves. Such corridors would then act as a con-

tinual drain on the populations living in more productive

patches (sources). Baranga (1991) describes an example of

this from east Africa. Corridors are also likely to be com-

munity filters in that only some members of the community

will be able to use them successfully (Downes et al. 1997;

Forman 1995; Laurance 1995). This bias will likely lead to

distortions in the community compositions on either end

of the corridor, with all of the potential negative effects, dis-

cussed earlier, that this entails. Corridors can in principle

be designed to be efficient transporters of individuals and

not suboptimal habitat space, but generally the specifica-

tions for this will be very species specific, and therefore not

conducive to community connnectivity. Lastly, it needs to

be mentioned that corridors can be expensive to incorpo-

rate into regional conservation efforts, and planning efforts

must weigh the potential benefits and disadvantages of land-

scape corridors. My guess is that most of the time the bene-

fits will prevail.

Conclusions

1. Rodents are ubiquitous and extremely diverse. They
   have suffered a large number of anthropogenic extinc-
   tions, 78.3% of which have been on islands.


2. In spite of the great need for conservation attention, the
   public remains largely indifferent and /or complacent

Issues in Rodent Conservation 461

Figure 38.5 View of Østerdalen at Evenstad, Hedmark, Norway, showing nu-
merous edges (ecotones) generated by natural landscape features (riparian zone,
altitudinal zonation of communities) and anthropogenic modifications (timber
harvesting, agriculture, experimental enclosures for investigating landscape in-
fluences on root voles (Microtus oeconomus). 12 June, 1990; photo by author.

Figure 38.6 Experimental landscapes at

Oregon State University used for studying

population dynamics and social behavior

of gray-tailed voles (Microtus canicaudus).

Corridors can be seen connecting some of

the habitat patches. June 1997; photo by

J. O. Wolff.