Does photoperiod influence the start of the fall migration of monarch butterflies?

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Rinnah Clark Patrick Guerra


By Rinnah Clark, Biology

Advisor: Patrick Guerra

Presentation ID: CC_7

Abstract: Every fall, Eastern North American monarch butterflies travel southwards from the northern ranges of their habitat to their overwintering grounds in Central Mexico. In this study, the question we asked was whether monarch butterflies use day length as an environmental cue to determine when they should begin the fall migration. To address this, we used fall monarch sighting data from the citizen science program Journey North (2,114 fall monarchs seen in the field from 2010-2017), and examined if there was any relationship between sightings and photoperiod (values taken from We predicted that fall monarchs should be sighted at photoperiods that are consistent with the onset of fall, e.g., < 12-13 hours of daylight. In addition, we predicted that the photoperiods at which monarchs will be seen at more northern latitudes would be longer than the photoperiods at which monarchs will be sighted at more southern latitudes. This should occur, as monarchs at more northern latitudes will have to leave earlier during the season, since they will have a further distance to travel to Mexico relative to their more southern conspecifics.

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