Showing papers by "Roger A. Baldwin published in 2006"

Predicting Raccoon, Procyon lotor , Occurrence Through the Use of Microhabitat Variables

Abstract: Recent increases in Raccoon ( Procyon lotor ) abundance have been implicated for decreased nesting success of songbirds and transmission of rabies. Understanding the relationship between occurrence and microhabitat factors should be helpful in managing this species, though our current understanding of this relationship is inadequate. Therefore, we conducted a study in western Tennessee during 2000–2002 to determine this association. Occurrence (capture) data were assessed from results of live trapping at 176 and 112 trap sites during winter and summer, respectively, at three sites. A maximum of 26 habitat variables were measured at each trap location; all grids were combined for statistical analyses to account for varying relationships between occurrence and microhabitat factors across different landscapes. Univariate and stepwise logistic-regression analyses were used to assess associations among microhabitat variables and occurrence. Resulting models were validated through the jackknife procedure. Predictive equations were constructed from logistic-regression models to compute capture probabilities. Univariate analyses yielded numerous significant variables with those representing forest characteristics and proximity to water generally the most significant. Strong concordance was observed between winter and summer seasons for most variables though several differed (number of large hardwood snags, ground dens, and plant food species, distance to potential water and roads). Such temporal variability was expected due to seasonal differences in habitat components and biological needs of Raccoons. Variables included in derived models were similar to those scoring highest in univariate analyses; classification rates for models (winter = 72%; summer = 78%) were among the highest recorded for generalist species. By accounting for landscape attributes and replicating across sites, more accurate and useful models were developed. Such models should provide the information required to effectively manage this species.

The effect of scent-station precipitation covers on visitations by mammalian carnivores and eastern cottontails

Abstract: The distribution and abundance of mammalian predators are difficult to monitor because of their elusive nature. One tool used to monitor predators is strategically placed tracking stations. Precipitation often renders tracking stations unreadable by obscuring tracks and other sign. In our study we sought to evaluate the feasibility of placing covers over stations to protect tracking surfaces from precipitation. Survival of the cover structures was negatively correlated with wind speed and positively correlated with woodlands. This suggested that covers might be best used in areas with low wind speeds and/or in forests or other sites that provide shelter from wind. Covers appeared to negatively affect visitations by coyotes (Canis latrans), bobcats (Lynx rufus), and eastern cottontails (Sylvilagus floridanus), but not raccoons (Procyon lotor) or Virginia opossums (Didelphis virginiana). Track quality was not substantially different for covered stations during light rain or snow.