osmiaCAM: A Low-cost Imaging Monitoring System for Linking Solitary Bee Foraging, Nest Provisioning, and...

While social bees are a primary focus of research and monitoring efforts among pollinators, more than 80% of bee species are solitary. For solitary bees, foraging behavior and efficiency directly impact the reproductive outcomes of individuals (fitness), as the consequences of foraging performance are not buffered by a colony. Cavity-nesting bees (e.g., Osmia spp. and Megachile spp. (Megachilidae)) progressively provision pollen in cells within hollow stems and other cavities, with each cell generally containing one offspring, making their reproductive output easily quantifiable. Cavity-nesting bees thus represent an ideal system to study fitness effects of individual variation in foraging niche, including differences in foraging activity and responses to environmental conditions. Understanding the links between individual performance and fitness can improve our understanding of solitary bee behavior, physiology, and ecology, particularly in response to environmental change. However, quantifying both foraging activity and provisioning rates within nests is prohibitively labor-intensive in many cases, especially for the extended time periods (i.e., weeks or months) over which nests are provisioned and under naturalistic ecological conditions. While recent work has established computer vision tools for automated monitoring of foraging activity at solitary bee nests, combining these approaches with in-nest monitoring could help better link foraging to fitness in solitary bees. Here we introduce Osmia Camera Activity Monitoring (osmiaCAM), a low-cost, open-source, automated monitoring system for foraging and nest-provisioning behavior of cavity-nesting bees, including key pollinator and research model organisms, such as Osmia spp. and Megachile spp. We demonstrate the potential of this system in a small validation experiment in Central California, where we quantified foraging transits and nest provisioning rates of Osmia spp. under variable weather conditions. This validation experiment yielded accurate, near-continuous monitoring for several weeks continuously. The osmiaCAM system has broad applications across cavity-nesting solitary bee species, facilitating research on their behavior, ecology, and responses to rapid environmental change. The development of autonomous monitoring systems and associated data analysis pipelines provides an opportunity for open-source ecological methods that would be applicable across a multitude of systems and disciplines.