Ethomics for Ecotoxicology: Automated Tracking Reveals Diverse Effects of Insecticides on Bumble Bee Foraging and In-Nest Behavior.

The majority of flowering plants depend on insect pollination for reproduction and declining pollinator populations pose a threat to biodiversity as well as critical crop pollination services globally. Widespread insecticide use negatively impacts pollinator physiology and behavior even at environmentally-realistic concentrations below lethal toxicity, leading to reduced fitness and long-term population declines. However, significant gaps remain in our understanding of how insecticides affect diverse aspects of behavior and ultimately influence pollinator populations and pollination services. These gaps partly stem from the challenge of quantifying sublethal effects of pesticides on the complex behavioral repertoires of insects. Current methods often focus on a narrow set of behaviors at a time, limiting our ability to capture the comprehensive range of impacts within management-relevant timescales. The emergence of low-cost techniques for high-throughput behavioral quantification, or "ethomics", holds enormous potential to address this knowledge gap. Here, we used automated, computer vision-based tracking implemented on open-source hardware (Raspberry Pis) to investigate the sublethal effects of an emerging "bee-safe" butenolide insecticide (flupyradifurone), as well as a neonicotinoid insecticide (imidacloprid), on bumble bee (Bombus impatiens) behavior. We simultaneously quantified the behavior of uniquely tagged individual workers both within the nest, and during foraging in a semi-field environment, to assess the holistic effects of insecticides under naturalistic conditions. Both insecticides increased mortality risk and altered behavior, but in distinct ways across behavioral contexts. Imidacloprid modified nest behavior by decreasing activity, while flupyradifurone altered spatial behavior within the nest (shifting bees toward the brood). Imidacloprid-but not flupyradifurone-reduced overall foraging activity, while both affected floral preference. Overall, our results highlight the complex potential mechanistic links between sublethal insecticide exposure, behavior, and pollinator health. This work emphasizes the need-and possibility-for rapid and holistic pesticide risk assessment under realistic environmental conditions using high-throughput ethomics, and could inform the development of sustainable agricultural practices and conservation strategies.