Flight Strategies of Migrating Monarch Butterflies (Danaus plexippus L.) in Southern Ontario

Abstract

Most migrating butterflies fly relatively close to the ground, presumably to avoid the full force of the wind and to better control their courses (Baker 1978; Walker 1980; Walker and Riordan 1981; Walker TJ 1985). In North America, the monarch butterfly, Danaus plexippus L., is a well-known exception. During the late summer and fall migration, individuals of this species regularly fly high above the ground (Beall 1941a, b; Gibo and Pallett 1979; Gibo 1981 ;Schmidt-Koenig 1984;Lugger 1980;Urquhart 1960) and often proceed by soaring flight (Gibo 1981; Gibo and Pallett 1979; Schmidt-Koenig 1979; Schmidt-Koenig 1985). The migrating D. plexippus can reach surprising altitudes, presumably by circling in thermals. Glider pilots have observed the butterflies flying more than 1 km above the ground (Gibo 1981). In addition to being the only North American butterfly known to migrate at high altitudes, D. plexippus also accomplish a remarkable feat of navigation. Each fall most of the eastern North American population make their way to a small group of overwintering sites in the mountains of central Mexico (Brower 1977; Calvert et al. 1979; Brower 1984; Urquhart and Urquhart 1976, 1977, 1978).