Habitat loss is a key factor in monarch butterfly population decline (Flockhart 2015). Monarch habitat restoration efforts are focused on increasing milkweed (Asclepias sp.) for oviposition and other native prairie plants as nectar sources. Utilization of these resources by monarchs and other pollinators is a function of detecting visual and/or olfactory cues and their associated search patterns. The focus of this project is to understand how monarchs are currently utilizing the landscape so that we can better implement guidelines for habitat restoration. New habitat should be planted to increase overall habitat connectivity based on detectability. Radio telemetry is a valuable technique for studying movement of animals when, as in this case, we need to measure movement patterns at distances several hundred meters from a human observer. We are employing active radio telemetry techniques to track monarchs in large scale landscapes to understand how monarchs “make decisions”. From this information, we will begin to understand typical flight distances between stopping for oviposition or nectar and the distance monarchs are able to detect resources (perception distance).
We observed radio-tagged and untagged monarchs to estimate transmitter attachment’s effect on normal behavior. Colony-reared (USDA-ARS Ames, IA) monarchs were not inclined to fly (2/10 tagged and 8/10 untagged flew), however, time spent resting and feeding were not significantly different between tagged and untagged individuals (two sample t-test; p = 0.12; p = 0.31, respectively). Field captured monarchs were more motivated to fly. Nine of 10 field captured monarchs flew with transmitters, with 10.5 ± 10.2% of the time spent flying. To track flight paths, a radio-tagged field-collected monarch was released in the center of a habitat patch surrounded by 4 technicians with antennas and receivers. Every minute, technicians simultaneously took a bearing in the direction of the strongest signal. Based on triangulation, bearings were used to calculate estimated locations with error ellipses. In 2016, thirteen monarchs were released individually and their locations were simultaneously triangulated for up to 103 minutes. Flight tracks were overlaid on the site with ArcMap. In summer 2017, operators will be stationed in habitats surrounding a prairie to track flight at habitat edges. Perception distance will be estimated as monarchs exhibit flight behavior directed towards host plants and/or nectar plant patches in a restored prairie.