Understanding the interactions between parasites, hosts, and their shared environment is central to ecology. Variation in infestation prevalence may be the result of varying environmental and population characteristics; however, variations in parasitism may also depend on individual characteristics that influence both the exposure and susceptibility to parasites. Using 12 years of data from a population of wild eastern chipmunks relying on pulsed food resources, we investigated the determinants of bot fly parasitism at both the population and individual level. We assessed the relationship between infestation prevalence and weather conditions, population size and food abundance. Then, we assessed the relationship between infestation intensity and chipmunk behavior, sex, age, body mass and food abundance. Precipitation, temperature and population size were positively related to infestation prevalence, while beech masts were negatively related to infestation prevalence, highlighting the importance of local environmental conditions on hosts and parasites. We also found that the influence of activity and exploration on infestation intensity varied according to sex in adults. More active and faster exploring males had more parasites compared to females, suggesting that reproductive behaviors may influence parasite exposure. For juveniles, infestation intensity was greater when juveniles emerged in the spring as opposed to fall, possibly because spring emergence is synchronized with the peak of bot fly eggs in the environment, low food availability and longer activity period. Our results suggest that the environmental, population and host characteristics that are advantageous for reproduction and resource acquisition may come at the cost of increasing parasitism.

了解寄生虫，宿主及其共享环境之间的相互作用对于生态至关重要。侵染率的变化可能是环境和人口特征变化的结果；但是，寄生虫的变化也可能取决于影响寄生虫暴露和易感性的个体特征。我们使用依赖于脉冲食物资源的野生东部花栗鼠种群的12年数据，调查了种群和个体水平上的蝇蝇寄生虫的决定因素。我们评估了侵染率与天气状况，人口规模和食物丰度之间的关系。然后，我们评估了侵染强度与花栗鼠行为，性别，年龄，体重和食物丰度之间的关系。沉淀，温度和种群数量与感染率呈正相关，而山毛榉桅杆与感染率呈负相关，突出了当地环境条件对寄主和寄生虫的重要性。我们还发现，活动和探索对侵扰强度的影响根据成年人的性别而异。与雌性相比，雄性更活跃且探索速度更快的寄生虫具有更多的寄生虫，这表明生殖行为可能会影响寄生虫的暴露。对于幼鱼来说，当春季出现幼虫而不是秋季时，侵扰强度会更大，这可能是因为春季出现与环境中的fly蝇卵高峰同步，食物供应不足和活动时间较长。我们的结果表明，环境，