The interplay between clumped resources, social aggregation, and genetic relatedness in the raccoon

Abstract

The extent to which individuals within a population live in groups is often variable, as group formation is most likely to occur when the benefits of group-living outweigh the costs. The distribution of resources can underpin the likelihood of group formation by altering costs associated with individuals aggregating. By influencing the extent of groupliving, resources may also influence relatedness patterns. To address this, we examined relatedness in raccoons (Procyon lotor) by combining spatial and genetic data in an experimental framework wherein resources were manipulated. We tested for differences in patterns of genetic relatedness among 12 sites subject to three treatments: no supplemental food; supplemental food added in a dispersed, non-predictable fashion; and clumped, predictable food supplements resulting in aggregations. We measured mean relatedness for >500 raccoons using blood and hair samples genotyped at 14 nuclear microsatellites and tested for differences between sites and sexes. For two sites, we radio-tracked raccoons and calculated volume of intersection (VI) values, which measure the probability of co-occurrence between individuals' home ranges, and calculated the relationship between VI and relatedness. Telemetry data indicated that raccoons exposed to clumped food shifted their home ranges, in turn perturbing patterns of relatedness between individuals, especially among females. This was exhibited through a positive association between VI and relatedness for females at the site with dispersed food, which was not observed among males or at the site with clumped food. At the landscape level, sites differed significantly in mean relatedness, but there were no clear patterns that corresponded to treatments. Overall, our observations support expectations of the resource dispersion hypothesis, wherein individuals modify ranges to include clumped resources if the costs of tolerating other individuals are low.

Supplementing non‐target taxa: bird feeding alters the local distribution of mammals

“…Squirrels and raccoons were more likely to be detected at sites with feeders than at nearby control sites, a result similar to previous food supplementation experiments that explicitly targeted mammals (Havera and Nixon , Sullivan , Schuttler et al. ). Because mammal populations in temperate environments can be food limited, particularly in winter, the novel food source unintentionally provided by humans via bird feeding can incentivize changes in movement patterns and feeding behaviors of mammals (Prevedello et al.…”

Variation in host home range size decreases rabies vaccination effectiveness by increasing the spatial spread of rabies virus

“…Dynamic, or elastic, home ranges reflect underlying spatiotemporal differences in demography, environmental conditions or territorial behaviour (Tao, Börger, & Hastings, ). Raccoon home range size can shift in response to underlying resources, such as concentrated food sources in urban areas (Schuttler et al, ) but the time‐scale of potential home range expansion and contraction remains understudied in most areas (although we note that GPS data from raccoons in Burlington, Vermont and Chattanooga, Tennessee both suggest that home range sizes varied weekly, USDA APHIS Wildlife Services, unpublished data). Our results suggest that dynamic home range sizes resulting from fluctuating resources could increase pathogen transmission and RABV spatial spread in resource‐subsidized raccoon populations.…”

When management meets science: adaptive analysis for the optimization of the eradication of the Northern raccoon (Procyon lotor)

“…This suggests a clumped distribution of raccoon in our study area (e.g. Wehtje and Gompper 2011;Schuttler et al 2015) and indicates that the nuclei of the species in those sites had not been completely removed during the first trapping season. Consequently, those sites were subject to an increase in capture effort in the next phase of the campaign.…”