Raccoon Social Networks and the Potential for Disease Transmission

Abstract

Raccoons are an important vector of rabies and other pathogens. The degree to which these pathogens can spread through a raccoon population should be closely linked to association rates between individual raccoons. Most studies of raccoon sociality have found patterns consistent with low levels of social connectivity within populations, thus the likelihood of direct pathogen transmission between raccoons is theoretically low. We used proximity detecting collars and social network metrics to calculate the degree of social connectivity in an urban raccoon population for purposes of estimating potential pathogen spread. In contrast to previous assumptions, raccoon social association networks were highly connected, and all individuals were connected to one large social network during 15 out of 18 months of study. However, these metrics may overestimate the potential for a pathogen to spread through a population, as many of the social connections were based on relatively short contact periods. To more closely reflect varying probabilities of pathogen spread, we censored the raccoon social networks based on the total amount of time spent in close proximity between two individuals per month. As this time criteria for censoring the social networks increased from one to thirty minutes, corresponding measures of network connectivity declined. These findings demonstrate that raccoon populations are much more tightly connected than would have been predicted based on previous studies, but also point out that additional research is needed to calculate more precise transmission probabilities by infected individuals, and determine how disease infection changes normal social behaviors.

Brown spider monkeys ( Ateles hybridus ): a model for differentiating the role of social networks and physical contact on parasite transmission dynamics

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Covariation between the physiological and behavioral components of pathogen transmission: host heterogeneity determines epidemic outcomes

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Which mechanisms drive seasonal rabies outbreaks in raccoons? A test using dynamic social network models

“…Recent research has led to the conclusion that raccoons are far more social than originally assumed (Gehrt & Fritzell ; Chamberlain & Leopold ; Gehrt & Fox ; Pitt, Lariviere & Messier ; Prange, Gehrt & Hauver ; Robert, Garant & Pelletier ); males are more social than females (Gehrt & Fritzell ; Chamberlain & Leopold ; Gehrt & Fox ; Pitt, Lariviere & Messier ); adult male–female and adult male–male contacts are more frequent and of longer duration during the winter breeding season (Gehrt & Fritzell ; Prange, Gehrt & Hauver ; Hirsch et al . ,b); and social contacts range from brief encounters to long‐term stable associations between pairs of individuals (Prange, Gehrt & Hauver ; Reynolds et al . ).…”