Raccoons (Procyon lotor) are one of the most adaptable and ubiquitous carnivore species, and thrive in both natural and heavily modified environments throughout their range. Their success in human-dominated landscapes makes them an ideal model species to investigate the impact of humans on wildlife populations. We monitored raccoons in an urban and recreational park in the Greater Miami Area of South Florida using both a capture-recapture procedure (85 individuals) and GPS tracking (12 collars) to understand their spatial behaviors in relation to human activities, and notably the park’s dumpsters. We first modeled their habitat selection using Resource selection functions, especially in relation to the dumpsters. We then used this information to investigate our first hypothesis linking the dumpsters to fitness components (body condition, relative density, and pathogen load). Second, we designed an Individual-based movement model informed by habitat selection and pathogen spread to investigate our second hypothesis on the influence of the dumpsters on spatial dynamics in the park.
Two habitat selection strategies emerged in raccoons, with a group selecting dumpsters and the other one avoiding them—while being very consistent in other aspects of selection. The selection of the dumpsters was directly related to the distance to the dumpsters. There was a clear impact of the dumpsters on fitness, as raccoons had better body condition, and local density was higher, close to the dumpsters. We are still investigating the effect on pathogen load. The simulation allowed us to remove the attraction effect of the dumpsters in the movement model, which revealed both an increase in home range size and a displacement to other areas of the park for individuals heavily associated to the trash, while increasing promiscuity between both strategies. Conversely, the presence of the dumpsters is associated to a reduced pathogen spread in the park, but also a increased infection risk for raccoons selecting the dumpsters. Although food supplementation has a clear effect in this population, our study depicts a more complex situation, with part of the population ignoring anthropogenic food resources, and raccoons only rarely venturing outside of the park. The high density recorded in the park can also potentially lead to spread of infectious diseases, which could counteract the potential benefit of living in an urban area with supplemental food. This study highlights how forward modeling (i.e. simulations parameterized with statistical models on observed data) can be used in movement studies to uncover specific ecological processes.
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Reference: Dejeante R., Joo R., Boone M. & Basille M. (2020) Trash pandas in their natural environment — Or how raccoons use and abuse human trash. 104th Ecological Society of America Annual Meeting 2020, Virtual meeting.