Landscape composition and structure influence the abundance of mesopredators: implications for the control of the raccoon (Procyon lotor) variant of rabies

Abstract

Rabies propagation in Canada has forced wildlife managers to develop intervention strategies to reduce the risk of rabies epizootics. We assessed whether some landscape characteristics of a corn-dominated region of Quebec in which the raccoon variant of rabies (RVR) has spread were associated with the abundances of raccoons ( Procyon lotor (L., 1758)) and striped skunks (Mephitis mephitis (Schreber, 1776)). We then examined whether landscape variables that best explained spatial variation in raccoon abundance were also good predictors in the detection of rabid raccoons. Between June and September 2007, 9600 raccoons and 1612 skunks were captured from 111 trapping cells. The abundance of captured raccoons, especially that of adult males and juveniles, increased over the summer in trapping cells characterized by a high density of forest edges bordering corn fields. The probability of detecting rabid raccoons also increased with this landscape characteristic, as well as with adult raccoon abundance. No landscape characteristic, however, explained spatial variation in skunk abundance. Efficient RVR control operations in similar landscapes should ideally include widespread distribution of vaccine baits because of the general distribution of skunks, while also focusing on areas where forest patches intersperse with corn fields to target high concentrations of raccoons, particularly in late summer.

ORAL RABIES VACCINATION OF RACCOONS AND STRIPED SKUNKS WITH ONRAB® BAITS: MULTIPLE FACTORS INFLUENCE FIELD IMMUNOGENICITY

“…Density estimation can be logistically challenging in a landscape designated for ORV control because these areas are often large, inherently having sufficient variation in raccoon densities to influence ORV efficacy given fixed bait densities. For raccoon rabies control, an apparently valid approach is to concentrate bait distribution in habitats empirically known to be associated with high raccoon densities (Houle et al, 2011), as this has been shown to increase the proportion of immunized raccoons (Robbins et al, 1998). In agriculturally fragmented landscapes, raccoons actively select forest cover (e.g., Beasley and Rhodes, 2010).…”

“…In agriculturally fragmented landscapes, raccoons actively select forest cover (e.g., Beasley and Rhodes, 2010). In these landscapes dominated by cornfields with a few forested patches, which are associated with the highest risks of raccoon rabies (Houle et al, 2011;Rees et al, 2011), transect experiments showed that contact rates of wildlife with baits were highest for ONRAB baits placed in forested habitats rather than along the edge or within adjacent agricultural fields. This pattern occurred especially in the fall and spring when raccoons accounted for half of the wildlife species observed near these baits (Boyer et al, 2011).…”

“…Baiting campaigns should especially take into account raccoon densities, which in turn are often related to the availability of their preferred habitats (see Houle et al, 2011). Accounting for these sources of variation should increase the proportion of individuals within a population that are immunized by ORV campaigns, while also minimizing costs (i.e., the number of vaccine baits used).…”

Raccoon (Procyon lotor) Activity is Better Predicted by Water Availability than Land Cover in a Moderately Fragmented Landscape

“…Raccoons are primarily associated with forest cover (e.g., Beasley et al 2007a, Chamberlain et al 2007, Gehring and Swihart 2003, but they attain their greatest densities in moderately forested landscapes rather than continuously forested ones (Oehler and Litvaitis 1996) and prefer to reside in areas characterized by heterogeneity in land cover (Byrne and Chamberlain 2011). Raccoons often use forest edges, particularly in moderately fragmented landscapes (e.g., Barding and Nelson 2008, Houle et al 2004, Renfrew and Ribic 2003, but whether they exhibit an edge effect likely depends on the type of edge, and local and seasonal resource availability (e.g., Dijak and Thompson 2000, Heske et al 1999, Newton and Heske 2001.…”

Born to be wild? Response of an urban exploiter to human-modified environment and fluctuating weather conditions

“…Raccoons (Procyon lotor (L., 1758)) are a quintessential example of an "urban exploiter" and, therefore, a model for understanding the effects of human activity on body mass. Raccoon population density is highest in heavily human-modified landscapes, such as urban centers (Riley et al 1998;Smith and Engeman 2002;Prange et al 2003), and in agricultural landscapes (Beasley et al 2011;Houle et al 2011). Artificial food sources, such as refuse and corn, are hypothesized to explain these high raccoon densities (Riley et al 1998;Prange et al 2004).…”