An experimental displacement and over 50 years of tag-recoveries show that monarch butterflies are not true navigators

Abstract

Monarch butterflies (Danaus plexippus) breeding in eastern North America are famous for their annual fall migration to their overwintering grounds in Mexico. However, the mechanisms they use to successfully reach these sites remain poorly understood. Here, we test whether monarchs are true navigators who can determine their location relative to their final destination using both a "compass" and a "map". Using flight simulators, we recorded the orientation of wild-caught monarchs in southwestern Ontario and found that individuals generally flew in a southwest direction toward the wintering grounds. When displaced 2,500 km to the west, the same individuals continued to fly in a general southwest direction, suggesting that monarchs use a simple vector-navigation strategy (i.e., use a specific compass bearing without compensating for displacement). Using over 5 decades of field data, we also show that the directional concentration and the angular SD of recoveries from tagged monarchs largely conformed to two mathematical models describing the directional distribution of migrants expected under a vector-navigation strategy. A third analysis of tagged recoveries shows that the increasing directionality of migration from north to south is largely because of the presence of geographic barriers that guide individuals toward overwintering sites. Our work suggests that monarchs breeding in eastern North America likely combine simple orientation mechanisms with geographic features that funnel them toward Mexican overwintering sites, a remarkable achievement considering that these butterflies weigh less than a gram and travel thousands of kilometers to a site they have never seen. mark-recapture | clock-and-compass orientation | numerical model | analytical expectation model | longitudinal displacement

Sun Compass Orientation Helps Coral Reef Fish Larvae Return to Their Natal Reef

“…The succession of orientation mechanisms suggested here for reef fish larvae is similar to the innate mechanisms used by birds and monarch butterflies during migration: first a compass mechanism based on global cues for the long-distance navigation phase followed by a homing process based on more local cues (e.g. [22], [24], [35], [36]). …”

“…However, thus far, no plausible mechanism has been demonstrated that could allow pelagic larvae to locate the natal reef from distances beyond a few kilometers after their initial period of passive dispersal during which they are not capable of sustained directional swimming. For longer distance directional movements, animals typically use an innate or acquired compass [18], [19], [20], [21], [22], [23], [24]. Thus, the aim of the present paper is to investigate whether reef fish larvae have a compass mechanism that could be helpful for long-distance homing.…”

Importance of the antenniform legs, but not vision, for homing by the neotropical whip spider,Paraphrynus laevifrons

“…However, the general success of the control and VD subjects in returning to their home refuge and, more importantly, the fact that they were released on the ground indicates that amblypygids can characteristically return to their home refuge following experimental displacement to unfamiliar locations. Finally, it is worth noting that despite the impressive distance of their migration, monarch butterflies do not count among the arthropod species that can re-orient following displacement, at least during migration (Mouritsen et al, 2013).…”

“…However, it is becoming increasingly apparent that despite their relatively small brains and generally shorter distances traveled (the monarch butterfly, Danaus plexippus, not withstanding; Mouritsen et al, 2013), many arthropod species also display an impressive navigational ability (Cheng, 2012;Collett and Graham, 2004;Boles and Lohmann, 2003;Layne et al, 2003). Indeed, both honey bees (Apis mellifera; Menzel et al, 2005) and an Australian ant species (Myrmecia croslandi; Narendra et al, 2013) have been shown to be able to return to their nests even after experimental displacement to unfamiliar locations, suggesting a cognitively rich navigational capacity.…”

Sensory basis of lepidopteran migration: focus on the monarch butterfly

“…The idea that migrant insects, such as the monarch, possess a map sense along with having different compass senses is unclear [13], especially given preliminary results from longitudinal displacement studies [6]. Future experiments testing the use of the magnetic compass as part of a geomagnetic map sense in monarchs, as seen in other animals that use an inclination magnetic compass [28–29], can help resolve this issue.…”