Geographic variation in swamp rabbit (Sylvilagus aquaticus ) home range and microhabitat characteristics

Joseph B Dumyahn, Purdue University

Abstract

Swamp rabbits (Sylvilagus aquaticus) are state-listed endangered mammals and no longer found in most of their historic range in Indiana. Despite this, knowledge of swamp rabbits in Indiana and throughout its range is limited. The purpose of this study was to: (1) estimate home range size for swamp rabbits in southwestern Indiana and compare that estimate to reported home range size estimates throughout the species’ geographic range; and (2) compare microhabitat characteristics of two distinct behavioral sites (form and latrine) used by swamp rabbits at the northern limit of the species distribution (southwestern Indiana and northwestern Kentucky) to areas within its core distribution (Arkansas). Mean fall/winter 95% fixed-kernel home range size, determined by radio telemetry, was 5.57 ha (SD = 3.91 ha) and 100% minimum convex polygon home range size was 2.98 ha (SD = 1.43 ha). This estimate was smaller than those previously reported in southwestern Indiana, but larger than other reported estimates throughout the swamp rabbit’s range. Differences among estimates may have been because of small sample size, methods used to calculate home range size, quality of habitat and inclusion of locations during flooding, which may increase home range size. Thirteen microhabitat characteristics measured at study sites in bottomland hardwood forests in southwestern Indiana and northwestern Kentucky during 2007-2008 were compared to legacy data collected in bottomland hardwood forests in Arkansas in 1991. There was a significant difference between form location characteristics at study sites in the northern study area and core study area (F = 0.08, p < 0.0001) and a significant difference among latrines in the northern study area and core study area (F = 0.29, p < 0.0001). Form locations at the core exhibited less canopy closure, more herbaceous vegetation, and more downed material than northern peripheral sites. This suggests that habitat in the north, where swamp rabbits are of concern, may lack key characteristics like canopy gaps and downed woody material important to the species. Latrine sites in the core had less canopy closure and greater overstory basal area than northern latrines. The core study area also had greater variation in canopy closure than the northern study area implying forests at the core were older and contained more mature trees. Uneven-aged silvicultural practices could be used to create such forest structure. Wildlife managers interested in increasing swamp rabbit populations should consider implementing practices that create such microhabitat components (i.e., canopy gaps, and downed woody material) that are favorable for swamp rabbits.

Degree

M.S.

Advisors

Zollner, Purdue University.

Subject Area

Ecology

COinS