Nature is not uniform: it shows "hot spots" and "cold spots" for any species or process. For example, in a forest patch with a moderately dense population of chipmunks, some particular sites ("hot spots") get visited by chipmunks much more often than others ("cold spots"). The existence of such hot and cold spots can affect processes such as how rapidly diseases are transmitted or whether or not a prey species goes extinct. This study takes the problem a step further, by specifically examining how the persistence of hot and cold spots affects the impact of white-footed mice and chipmunks on their prey (gypsy moths and ground-nesting birds) and parasites (ticks and Lyme disease bacteria). Populations of these rodents will be manipulated to create permanent (3 years) and temporary (1 year) cold spots, and survival of their prey and infection prevalence of ticks will be compared between the two treatments.
The research will show how the persistence of hot and cold spots of pivotal small mammals affects human health (Lyme disease risk), forest health (gypsy moth outbreak risk), and abundance of songbirds. The project will contribute to primary education through a web-based resource created in collaboration with educators and targeted toward grades 6-12. The project will also provide research training for both undergraduate and graduate students. Finally, the research will inform efforts to enhance biological pest control, conserve rare species, or reduce spread of diseases.
The suitability of the environment for plant or animal species differs from place to place, and these differences can affect how species affect each other. Suitability is usually considered over large areas, but even small-scale differences could amplify disease transmission or enable rare species to persist, particularly for animals that rarely move far. Our objectives were to measure and test how small-scale patterns of two ecologically important rodents (white-footed mice and chipmunks) affect their prey (gypsy moths) and their parasites (blacklegged ticks that carry Lyme disease). We used track plates to measure rodent activity across six well-studied oak-forest plots in upstate New York, 2008-2010. To uncover why some areas are rodent "hot spots" (high activity) and others are "cold spots", we compared local rodent activity to availability of food (seeds and arthropods) and cover. We also tried to create local "cold spots" by removing rodents in small areas. We searched the plots extensively for gypsy moth larvae and egg masses each year, measured attacks on gypsy moth pupae (mostly by mice), and tested nymphal blacklegged ticks for Lyme-disease infection. The interaction web explored by this research inspired educational materials aimed at helping students understand the workings of complex ecological systems, because familiar organisms have impacts that directly affect people. Mouse and chipmunk populations were low to moderate during the 3 years of field work, and their local activity varied substantially from point to point within our study areas. Mouse "hot spots" typically had thick brush and abundant arthropods, so both food and cover were important. Our attempts to create rodent "cold spots" were unsuccessful: removal spots had slightly higher activity of both species, perhaps as neighboring animals moved in. However, spots where we applied the same treatment (removal or not) over all 3 years had more consistent patterns of rodent activity than where we changed treatments each year, so we successfully manipulated the consistency of the rodent activity pattern over years. Local track activity of mice was a good predictor of predation on gypsy moth pupae, and we tended to find gypsy moth egg masses in spots meeting two conditions in early to mid-summer: 1) there were several caterpillars nearing the pupal stage and 2) there were few mouse tracks. The time window lasted 6 weeks, which makes sense because gypsy moths entered the pupal stage over a wide time range. Therefore, we showed that small-scale differences in mouse activity create refuges where gypsy moths could persist. We collected the most blacklegged tick nymphs in areas with moist conditions and dense ground vegetation, but nymph abundance was not related to past activity of mice or chipmunks. The fraction of ticks carrying Lyme-disease bacteria was weakly related to past mouse activity at the scale of our plots, but not at smaller scales. Therefore, we did not find that small-scale variations in small mammal activity strongly affected the abundance of Lyme-disease carrying ticks, at least over the two years we studied this. Food chains and food webs are frequently taught in schools, yet most students cannot apply these ideas to real organisms in their local environment, nor use these concepts to understand how ecosystems respond to environmental change. We found that 6th and 7th grade students understand simple links between pairs of species, but often don’t recognize that influences go both ways, extend to other species, or vary in strength and over time. We used these findings to craft an interactive web-based curriculum module for students to explore the complexities of the "acorn connection" and apply their new understanding to other ecological interactions. The module, soon to be available on the Cary Institute’s website, includes 4 chapters and instructions for complementary field studies. The module was pilot tested in two middle schools and one high school in 2011, with 6 teachers and 413 students participating. Also, a Cary Institute educator went into the classrooms and taught a hands-on lesson based on the Lyme module. The pilot results are being used to assess student thinking about complex ecological interactions, and to shape the final version of the Module. In term of broader impacts, this project is the first to specifically attempt to manipulate consistency (over time) of the spatial pattern of animal activity, and to measure predicted consequences. Despite confirming some hypothesized relationships at small scales, our findings highlight the difficulty of observing and predicting patterns at small spatial scales, even when such small scales may be important. This project has provided important field and laboratory experience to 25 undergraduates, 8 graduate students, 2 volunteers, and 7 technical professionals, and has led to or is leading to numerous scientific publications. The education program has provided a novel approach to teaching ecological complexity in schools.
