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Abstract
Decisions made during oviposition and migration have critical fitness implications for monarch butterflies (Danaus plexippus). The presence of conspecifics or cues left behind can indicate desirable resources, and provide energetically-inexpensive information. We examined female monarch response to conspecific eggs across swamp milkweed (Asclepias incarnata) stalks of differing physical quality. Additionally, we asked whether monarchs reared under different conditions would orient more accurately as conspecific group size increased. Females did not change their oviposition behavior in response to social cues, neither avoiding nor preferring stalks containing conspecific eggs regardless of host-plant quality. During flight trials however, group size had a significant, positive effect on orientation, suggesting that conspecifics improve monarch navigation. These results provide novel evidence of social information use by monarchs, and indicate that social cue use may be situational, or dependent on larval rearing environment. Future work could further examine the link between rearing environment, genetics, and social behavior.