Populations of Blarina brevicauda were monitored in three habitat types: restored tallgrass prairie (March 1972–May 1997), bluegrass (Poa pratensis; January 1972–May 1997), and alfalfa (Medicago sativa; May 1972–May 1997).
Study sites
Dry weight of vegetation in the study sites for trapping (clipped at the surface of 26 randomly located 0.25-m2 plots) was used to determine relative abundances of plants.
1. Two restored tallgrass prairies, located in Trelease Prairie (established in 1944) and Phillips Tract respectively. Trelease Prairie was bordered by a mowed lawn, cultivated fields, forbs and shrubs, and a macadam county road, until 1980, when the cultivated field to the south was converted to grazed pasture. The prairies were burned during the spring at 3- to 4-year intervals to set back invading shrubs and trees. Relative abundances of plants:
Trelease Prairie: 17% - big bluestem (Andropogon gerardii), 16% - bush clover (Lespedeza cuneata), 12% - ironweed (Veronia),10% - Indian grass (Sorghastrum nutans), 9% - milkweed (Asclepias), 9% - goldenrod (Solidago), 5% - bluegrass, 5% - switch grass (Panicum), 2% - blackberry (Rubus), 2% - little bluestem (Andropogon scoparius), 1% - about 10 other species.
Phillips Tract site (Sep. 1977): 38% - A. gerardii, 25% - L. cuneata, 16% - Beard tongue foxglove (Penstemon digitalis), 19% - S. nutans (19%), 1% - all other species.
2. The study sites for bluegrass were set up within a former bluegrass pasture in Phillips Tract. The pasture ceased to be used for grazing in June 1971, and by the fall of the same year, it had developed a dense vegetation cover. Bluegrass sites, along with the entire area, were mowed during late summer every 2–3 years, cutting the vegetation at about 25 cm above the surface to suppress growth of invading forbs and woody vegetation. Tall grass was uncut.
Relative abundances of plants was relatively unchanged throughout 1972-1994: 70% - Bluegrass, 14% - dandelion (Taraxacum officinale), 4% - wild parsnip (Pastinaca sativa), 3% - goatsbeard (Tragopogon), 1% - about 20 other species.
Relative abundance of plants changed between 1995-1997: 75% - brome grass (Bromus inermis), 20% - Timothy (Phleum pratense).
3. Two study sites with alfalfa, separated by a 10-m closely mown strip to limit home ranges of animals whose nests were in one field to extend into the other field. However, animals moved between the two sites and a single population was monitored. Initially, alfalfa comprised 75% of the vegetation in each site. 3-m-wide strips were mowed 25 cm above the surface each summer (early June through mid-September) to control invading weedy forbs and promote new growth of alfalfa plants. Times of mowing were determined so that at least two-thirds of the field was always densely covered by live vegetation and recently mown litter. When alfalfa began to be dominated by invading forbs and grasses on one site, the other side was planted to alfalfa so that the alfalfa would be fully developed when trapping commenced in that site.
Procedures
The procedure was designed for monitoring population of voles. All study sites were organized on a grid system with 10-m intervals. One wooden multiple-capture live-trap was used at each station. Every month, a 2-day prebaiting period was followed by a 3-day trapping session, except for August 1975 to December 1976 when trapping occurred every 3 weeks at each site.
Since the study was designed for voles, cracked corn was used both for prebaiting and as bait in the traps. Cracked corn is not a suitable food for shrews. Vegetation or aluminum shields were used to protect traps from the sun during summer, while the wooden traps provided insulation in winter so nesting material was not provided in the traps at any time. Total trap mortality was estimated to be 40.1%. Trap mortality had an impact on the shrew populations, but did not disrupt the overall dynamics of the population study.
Traps were set in the afternoon. Over the following three days, recordings were taken at approximately 0800 h and 1500 h of voles. Because of their pointed noses, many Blarina were able to escape from the multiple capture traps used to trap voles. All live shrews were toe-clipped (maximum of 2 toes on each foot) at first capture for individual identification and so recorded in the data sheets.
The field protocol, which included toe clipping, was in accordance with the guidelines set by the University and Federal authorities, as well as recommendations from the American Society of Mammalogists in effect at that time. The field protocol was reviewed and approved periodically by the Laboratory Animal Resource Committee at the University of Illinois throughout the duration of the study.
Blarina brevicauda did not enter traps until they were at least three-fourths grown. Therefore young animals could not be distinguished from small adults and thus, the data were not separated by age class.
References for data of the vole study:
Getz, L.L. 2024. Monitoring of Microtus ochrogaster and Microtus pennsylvanicus populations in three different habitats in east-central Illinois, 1972 to 1997. ver 2. Environmental Data Initiative. https://doi.org/10.6073/pasta/62617e944d053ba553d37cc4568c2367.
Getz, L.L. 2024. Twice weekly monitoring of a Microtus ochrogaster population and social behavior in alfalfa in eastern Illinois, 1982-1987. ver 1. Environmental Data Initiative. https://doi.org/10.6073/pasta/e62ec4197e8e2a687f2ef9d2c13cc3c0.
