Small mammal response to oak savanna restoration in northwest Indiana

Valerie J Clarkston, Purdue University

Abstract

The first objective of this thesis was to determine if differences existed in the composition of the small mammal community in oak savannas relative to the community found in adjacent oak woodland. Specifically, from June to August 2009, I estimated and compared abundance, density, and micro-habitat affiliations of small mammals in two oak savanna and four oak woodland sites at the Jasper-Pulaski State Fish & Wildlife Area in northwest Indiana. I also conducted separate surveys to detect eastern cottontails ( Sylvilagus floridanus) and plains pocket gophers (Geomys bursarius). My results showed similar abundance between oak woodland and savanna for white-footed mice (Peromyscus leucopus), eastern chipmunks (Tamias striatus), and fox squirrels ( Sciurus niger). However, southern flying squirrels (Glaucomys volans) and North American red squirrels (Tamiasciurus hudsonicus ) were captured only in oak woodlands whereas pocket gopher mounds and eastern cottontails were detected solely in the oak savanna sites. Basal area of oaks (Quercus spp.) was a positive predictor for both the southern flying squirrel and red squirrel at my study site, most likely because these two species rely on greater density of trees either for efficient movement or protection from predators. In contrast, the low density of trees found in the oak savanna sites allowed pocket gophers to successfully create tunnel systems without being impeded by numerous tree root systems. Eastern cottontails captured in the oak savanna sites most likely used these areas to forage on the succulent vegetation that grew in these sites as a result of the more openly-grown trees that allowed sufficient light to penetrate to the ground. A second objective of my thesis was to determine the short-term response of small mammals to the conversion of two of the four previously mentioned oak woodland sites to oak savanna via mechanical removal of woody vegetation followed by prescribed burning. I used the same locations I sampled during 2009. However, for this part of my research I split my study area into three treatment types: (1) no disturbance (Control); (2) existing oak savanna (Target); and (3) woodlands converted to savanna (Restoration). I predicted woodland obligate species, such as southern flying squirrels, red squirrels, and eastern chipmunks, would be negatively impacted by the conversion of woodland to savanna, whereas cottontails and gophers would benefit from creation of oak savanna habitat. I predicted that the mouse (Peromyscus spp.) and fox squirrel populations would remain the same following the conversion of oak woodland to oak savanna. I sampled each treatment from May to August 2011 using the same methods described above with the addition of snow-track surveys for rabbits, passive acoustic sampling for bat activity, and trap specific measurements of micro-habitat characteristics. The restoration processes opened the canopy, eliminated most woody stems and herbaceous vegetation, and consumed all leaf litter. Southern flying squirrels, meadow voles (Microtus pennsylvanicus), and northern short-tailed shrews (Blarina brevicauda) were almost entirely absent from Restoration sites following conversion to savanna. Important micro-habitat characteristics, such as leaf litter and dense herbaceous cover, were absent from the Restoration sites, possibly explaining the absence of these 3 species. Fox squirrel abundance decreased from 2009 to 2011, but this species was captured more frequently in the Restoration treatment, as compared to the other two treatments, following conversion of oak woodland to oak savanna. The mouse (Peromyscus spp.) population increased from 2009 to 2011 regardless of treatment type. Gophers, cottontails, and bats were more active in the existing oak savannas compared to the recently restored sites, indicating that more iterations of disturbance may be required to improve suitability of the Restoration sites for these species. Results from my study suggest that the long-term benefits of establishing oak savannas outweigh the short-term negative effects caused by the restoration procedure. The interval between prescribed burns is important when attempting to manage and maintain a healthy small mammal community. As evidenced in Target treatments, a fire regime of burning, at a minimum of every three years, allowed the re-establishment of suitable micro-habitat to support many species typically found in the undisturbed woodlands. These considerations will allow habitat managers to restore oak savanna and maintain species diversity within an area without risking possible extirpation of some species. (Abstract shortened by UMI.)

Degree

M.S.

Advisors

Zollner, Purdue University.

Subject Area

Wildlife Conservation|Wildlife Management|Ecology

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