and hawthorn may be found. Unless the timber is heavy and con- 
nected with a tract of wooded bluff it seems to make little or no 
difference in the mammals found. Among those found at present 
in the county, only the muskrat and the mink can be truly at home 
in these flood-plains at all times; but a number of small animals are 
abundant in these localities during the summer. White-footed 
wood-mice and short-tailed shrews (Blarina brevicauda) are found 
wherever the ground is dry and shelter, in the form of driftwood, 
stumps, etc., is present. Prairie-voles are common down to the 
zone of the sedges, but seldom in that zone or below it. Weasels 
hunt over the bottoms, and rabbits hide there. The more heavily 
timbered portions are a favorite resort of coons. 
As the river-bottoms were in general the last portions of the coun- 
try from which, at a certain stage in the development of this part 
of the country, the original heavy timber was removed, they fur- 
nished a last retreat for deer and other large game. 
What becomes of the smaller mammals when these plains are 
under water? During the spring floods I have found voles clinging 
to the stumps that rose above the water. When approached they 
plunged into the water and swam off, or escaped by diving. I am 
told that in high water on the Ilinois River, many white-footed 
wood-mice are seen on the trees above the water. Probably the 
mice and shrews both escape in a similar way in this locality during 
floods. The runways of moles are common along the edge of the 
flood-plain, but almost never occur at any great distance below 
high-water mark. In fact, their presence serves as a reliable guide 
to the limit of ordinary high water. 
In spite of the fact that these small mammals swim so easily, 
the time of flood must be one of great mortality among them. The 
flood-plains are often forty rods or more across, and these animals 
are not strong enough swimmers to breast a moderate current, nor 
is it likely that they can live in the water a long time. Moreover, 
the time of high water is quite often the breeding season of these 
animals, and the very young must all perish. In the case of the 
comparatively small bottom-lands in this county it might be sup- 
posed that the mammalian population was kept up by immigration 
each summer from the surrounding higher ground, but that can 
hardly be true for the extensive tracts submerged each year along 
the Illinois and other large rivers. 
