Je. Diffendorfer et al., HABITAT FRAGMENTATION AND MOVEMENTS OF 3 SMALL MAMMALS (SIGMODON, MICROTUS, AND PEROMYSCUS), Ecology, 76(3), 1995, pp. 827-839
We studied the effects of habitat fragmentation on the movements of co
tton rats (Sigmodon hispidus), deer mice (Peromyscus maniculatus), and
prairie voles (Microtus ochrogaster) living in a fragmented landscape
using 7.7 yr (1984-1992) of mark-recapture data. The study area inclu
ded three kinds of 0.5-ha blocks: single large patches (5000 m(2)), cl
usters of medium patches (288 m(2)), and clusters of small patches (32
m(2)). We tested three predictions regarding animal movements. First,
animals should move longer distances as fragmentation increases. Seco
nd, the proportion of animals moving will decrease as fragmentation in
creases. Third, species will show more movement from putative sources
to putative sinks. In support of our first two predictions, all specie
s (except male cotton rats) moved farther, and lower proportions of an
imals moved, as fragmentation increased. In testing our third predicti
on, we found no trends, for all species, between patch size and the ne
t number of animals a block either imported or exported, indicating so
urce-sink dynamics were probably not occurring on our study site. Furt
hermore, animals of all species (except female deer mice) switched mor
e frequently to blocks of larger patches. For prairie voles in the spr
ing and deer mice in the summer, relative abundances among blocks pred
icted from a Markov matrix model of switching probabilities showed hig
h congruence with the actual abundances, indicating movement and abund
ances were related. In both cotton rats and prairie voles but not in d
eer mice, more juveniles and nonreproductive animals switched between
blocks than did adults or reproductive animals. Deer mice switched mor
e frequently than did either cotton rats or prairie voles; the latter
species switched in similar frequencies. We discuss the implications o
f our data for modeling and conservation.