Post provided by Kelsey E. Fisher
Kelsey Fisher describes the motivations and challenges in the development of a novel automated radio telemetry method to track the movement of butterflies at the landscape scale published in their new Methods article ‘Locating large insects using automated VHF radio telemetry with a multi‐antennae array’.
Understanding animal movement across varying spatial and temporal scales is an active area of fundamental ecological research, with practical applications in the fields of conservation biology and natural resource management. Advancements in tracking technologies, such as GPS and satellite systems, allow researchers to obtain more location information for a variety of species than ever before. It’s an exciting time for movement ecologists! However, entomologists studying insect movement are still limited because of the large size of tracking devices relative to the small size of insects.
Monarch butterflies are at risk of quasi-extinction, in part, from the loss of breeding habitat. Our research team’s effort at Iowa State University, funded by a USDA-NIFA grant in collaboration with the Iowa Monarch Conservation Consortium, aims to establish a sound scientific foundation for Iowa’s monarch butterfly conservation. Habitat restoration efforts include increasing native prairie plants for adult forage and milkweed (Asclepias spp.) for oviposition and larval development. Breeding-season monarch butterflies in the United States are highly mobile and females are not patch residents. Therefore to explore the impact of spatial arrangement of restored habitat on monarch butterfly movement and egg-laying behavior across the Iowa landscape an agent-based model was developed (Grant et al. 2018). However, model parameters were based on expert opinion and observations on monarch flight patterns within small, artificial fields and no empirical evidence of monarch movement at a landscape scale was available to evaluate model simulations. Improved understanding of how monarchs move through the landscape and utilize resources can provide better parameter estimates and support the development of biologically relevant habitat restoration plans.
In 2016, we began considering how to improve estimates of model input parameters and the extent which model simulations were representative of monarch flight paths at the landscape scale. These brainstorming sessions lead us to wonder if we could track wild monarchs across the Iowa landscape to provide evidence that supports the model. Observing landscape-scale movement of butterflies with only binoculars is difficult, if not impossible, so we turned to an unconventional approach for entomologists. Armed with handheld VHF radio telemetry equipment, very small transmitters (0.25 g), and butterfly nets, we headed to a restored prairie. We successfully estimated the locations of 13 radio tagged monarchs every minute for up to 30 minutes, recreated their flight paths, and estimated habitat utilization with continuous time movement models (Fisher et al. 2020). While this was an advancement in insect tracking, our methods were still limited by personnel requirements, spatial area coverage, and temporal resolution.
The use of automated systems has been suggested to increase scalability and data collection intervals, while potentially reducing errors in location estimates (Kissling et al. 2014). Our research group developed and employed an automated radio telemetry system from commercially available equipment designed to increase the frequency of data collection for flying insects, using the monarch as a model species. We modeled our design after a customized, automated system deployed in Panama successfully tracked 38 avian and mammalian species (Kays et al. 2011).
The five-year process of developing this automated radio telemetry method was full of challenges including long, hot Iowa summers, unpredicted extreme weather conditions, some heavy lifting, extensive data collection, and approaches to manage complex datasets. Developing this system was an exercise in creativity from designing the tower system and figuring out how to attach and stabilize the antennae, fitting the equipment in field vehicles, collaborating with landowners, to finally figuring out how to collect calibration data (see pictures of transmitter attached to hat). Our team persisted to push the technology and statistical approaches to the limit and provided a substantial methodological advancement for locating butterflies that can act as a benchmark as technology improves.
Our research team saw a gap in understanding of butterfly movement at the landscape scale and developed a method to provide an incremental improvement in the knowledge base. The information acquired by our team is valuable for refining predictions of realized fecundity estimated with the agent-based model and developing restoration recommendations to increase monarch habitat connectivity at a landscape scale. We look forward to hearing feedback on our system from the movement ecology and entomology communities. We are excited to see how our approach recently published in Methods in Ecology and Evolution will improve and welcome the opportunity for collaboration in the future.
To find out more about animal movement ecology and methods to track butterflies and other insects, read the Methods in Ecology and Evolution article by Fisher and colleagues, ‘Locating large insects using automated VHF radio telemetry with a multi‐antennae array’