Employing Very High Frequency (VHF) Radio Telemetry to Recreate Monarch Butterfly Flight Paths.

William Morrison,James S Adelman,Steven P Bradbury,Kelsey E Fisher

doi:10.1093/ee/nvaa019

Abstract

The overwintering population of eastern North American monarch butterflies (Danaus plexippus) has declined significantly. Loss of milkweed (Asclepias sp.), the monarch's obligate host plant in the Midwest United States, is considered to be a major cause of the decline. Restoring breeding habitat is an actionable step towards population recovery. Monarch butterflies are highly vagile; therefore, the spatial arrangement of milkweed in the landscape influences movement patterns, habitat utilization, and reproductive output. Empirical studies of female movement patterns within and between habitat patches in representative agricultural landscapes support recommendations for habitat restoration. To track monarch movement at distances beyond human visual range, we employed very high frequency radio telemetry with handheld antennae to collect movement bearings on a biologically relevant time scale. Attachment of 220-300 mg transmitters did not significantly affect behavior and flight capability. Thirteen radio-tagged monarchs were released in a restored prairie, and locations were estimated every minute for up to 39 min by simultaneous triangulation from four operators. Monarchs that left the prairie were tracked and relocated at distances up to 250 m. Assuming straight flights between locations, the majority of steps within the prairie were below 50 m. Steps associated with exiting the prairie exceeded 50 m with high directionality. Because butterflies do not fly in straight lines between stationary points, we also illustrate how occurrence models can use location data obtained through radio telemetry to estimate movement within a prairie and over multiple land cover types.

Highlights

Comments This article is published as Fisher, Kelsey E., James S
Because butterflies do not fly in straight lines between stationary points, we illustrate how occurrence models can use location data obtained through radio telemetry to estimate movement within a prairie and over multiple land cover types
Tracking technology adapted for flying insects creates an opportunity to quantify movement at larger spatial scales. Application of this technology can advance understanding of how butterflies move at habitat patch edges within landscape scales

Summary

Introduction

Comments This article is published as Fisher, Kelsey E., James S. Females produce 300–400 eggs (Urquhart 1960, Oberhauser 2004) that are typically laid singly per milkweed ramet (Zalucki and Kitching 1982a) Given these behaviors, the spatial arrangement of milkweed in the landscape is expected to influence movement patterns, habitat utilization, and reproductive output (Bergin et al 2000, Misenhelter and Rotenberry 2000, Pitman et al 2018, Grant and Bradbury 2019). Animal movement models are based on correlated random walk algorithms without incorporating behavioral factors (Siniff and Jessen 1969, Smouse et al 2010, Zhao et al 2015) These algorithms can be problematic in heterogeneous landscapes that require flight direction decisions at habitat edges in the mosaic of cropland, pastures, conservation land, and roadside rights of way in the monarch’s summer breeding range (Grant et al 2018).

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