Influence of habitat quality and resource density on breeding‐season female monarch butterfly Danaus plexippus movement and space use in north‐central USA agroecosystem landscapes

Abstract

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Monarch Butterfly Ecology, Behavior, and Vulnerabilities in North Central United States Agricultural Landscapes

“…Although prior work suggested natural flight step length should differ on the basis of habitat class, similar to the way turn angles do (Zalucki and Kitching 1982a , Zalucki 1983 , Delattre et al 2010 , Schultz et al 2012 , 2020a, Evans et al 2020b , Kral-O'Brien and Harmon 2021 ), we observed no difference in step length, with 90% of all steps measuring less than 50 m (Fisher et al 2020a , Fisher and Bradbury 2022 ). Using radio telemetry, we were able to quantify large emigration step lengths (i.e., the remaining 10% of steps; Fisher et al 2020a , Fisher and Bradbury, 2021 , 2022 ) that were previously only theorized (Crone and Schultz 2022 ). Long-distance emigration occurred periodically via single steps with lengths from 50–1900 m and was initiated from well within the habitat class boundaries (i.e., not because the butterfly intercepted the boundary while foraging).…”

“…In a series of studies, we observed wild-captured breeding-season females under field conditions in free-flying, radio-telemetry experiments (supplemental figure S10) and in tethered-flight trials (supplemental figure S11). In automated (Fisher et al 2021 , Fisher and Bradbury 2022 ) and handheld radio-telemetry studies (Fisher et al 2020a , Fisher and Bradbury, 2021 , 2022 ), we documented temporally and spatially fine-grained movement paths of female monarchs within habitat classes of varying resource quality and composition. We aimed to better understand monarch butterfly movement patterns, including natural step lengths (distance between two stopping locations), directionality in association with habitat classes, and the perceptual distance relative to nectar and milkweed resources.…”

“…Our research demonstrated that, as we anticipated, turn angles differed in high-density and low-density habitats (defined in table 2 ). Monarchs in resource-devoid habitats, such as sod fields (Fisher and Bradbury 2021 ) and crop fields (Fisher and Bradbury 2022 ), traveled in straight lines as evidenced by small turn angles, suggesting they do not waste time and energy searching for resources where they are unlikely to be encountered. Conversely, the flight paths were torturous when the monarchs were in high-density habitat and surrounded by milkweed and nectar resources, reminiscent of the looping, foray flight patterns described by Conradt et al ( 2003 ).…”

“…Conversely, the flight paths were torturous when the monarchs were in high-density habitat and surrounded by milkweed and nectar resources, reminiscent of the looping, foray flight patterns described by Conradt et al ( 2003 ). However, monarchs within intermediate-density habitats traveled with a high degree of directionality between clusters of resource plants (Fisher and Bradbury 2022 ). When the monarchs were moving among resource plants, foraging was the dominant behavior, suggesting that the monarchs were efficient at locating resources when they were surrounded by a grass-dominated land cover in an intermediate habitat class.…”

“…When the monarchs were moving among resource plants, foraging was the dominant behavior, suggesting that the monarchs were efficient at locating resources when they were surrounded by a grass-dominated land cover in an intermediate habitat class. These findings suggest that movement patterns are likely a product of resource density and distribution, because the resources were not evenly distributed within the habitat classes (Fisher and Bradbury 2022 ).…”