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To whom it may concern:

This folder contains two major sets of data files of the results of a 25-year study (1972-1997) in which populations of the prairie vole (Microtus ochrogaster) and the meadow vole (M. pennsylvanicus) were live-trapped at trapped monthly intervals in three habitat types (alfalfa, bluegrass and tallgrass prairie) in east-central Illinois, USA: (1) cleaned raw data files of individual captures for each trapping session and (2) cleaned compilation sheets of the individuals captured each trapping session—one entry per individual (Animals present but not captured a given month not entered).

Dr. Madan Oli and his student, Arpat Ozgul, have completed mark-recapture modeling on the 25-year data sets. Results of these analyses are available from Dr. Oli.

Two shorter term studies were made of (1) effects of supplemental feeding on prairie and meadow voles in bluegrass and tallgrass prairie habitats and (2) effects of interspecific competition in bluegrass (both species) and tallgrass (meadow vole). The interspecific competition study involved removal of animals from the control sites. These “Removal” data files are also included as they show monthly immigration of individuals into a vacated site.


All study sites were organized on a grid system with 10-m intervals. One wooden multiple-capture live-trap (Burt 1940) was placed at a station. Each month a 2-day prebaiting period was followed by a 3-day trapping session. Cracked corn was used for prebaiting and as bait in traps. We used vegetation or aluminum shields to protect traps from the sun during summer. Wooden traps provided ample insulation in winter, and thus we did not provide nesting material in the traps at any time. We estimated trap mortality to be <0.5%.
Traps were set in the afternoon and checked at about 0800 h and 1500 h on the following 3 days. All animals were toe-clipped (<2 toes on each foot) at 1st capture for individual identification. Although toe clipping no longer is a recommended method of marking animals, during most of the time of the study, few alternative methods were available. Ear tags were available, but owing to frequent loss of tags, toe clipping was deemed a more effective means of marking individuals. The field protocol, including use of toe clipping, was reviewed periodically by the University of Illinois Laboratory Animal Resource Committee throughout the study. The committee approved the field protocol, based on University and Federal guidelines, as well as those recommended by the American Society of Mammalogists, in effect at the time.
Species, individual identification, grid station, sex, reproductive condition (males: testes abdominal or descended; females: vulva open or closed, pregnant as determined by palpation, or lactating), and body mass to the nearest 1 g were recorded at each capture.