Unraveling the World’s Longest Non-stop Migration: The Indian Ocean Crossing of the Globe Skimmer Dragonfly

Abstract

Insect migration redistributes enormous quantities of biomass, nutrients and species globally. A subset of insect migrants perform extreme long-distance journeys, requiring specialized morphological, physiological and behavioral adaptations. The migratory globe skimmer dragonfly (Pantala flavescens) is hypothesized to migrate from India across the Indian Ocean to East Africa in the autumn, with a subsequent generation thought to return to India from East Africa the following spring. Using an energetic flight model and wind trajectory analysis, we evaluate the dynamics of this proposed transoceanic migration, which is considered to be the longest regular non-stop migratory flight when accounting for body size. The energetic flight model suggests that a mixed strategy of gliding and active flapping would allow a globe skimmer to stay airborne for up to 230–286 h, assuming that the metabolic rate of gliding flight is close to that of resting. If engaged in continuous active flapping flight only, the flight time is severely reduced to ∼4 h. Relying only on self-powered flight (combining active flapping and gliding), a globe skimmer could cross the Indian Ocean, but the migration would have to occur where the ocean crossing is shortest, at an exceptionally fast gliding speed and with little headwind. Consequently, we deem this scenario unlikely and suggest that wind assistance is essential for the crossing. The wind trajectory analysis reveals intra- and inter-seasonal differences in availability of favorable tailwinds, with only 15.2% of simulated migration trajectories successfully reaching land in autumn but 40.9% in spring, taking on average 127 and 55 h respectively. Thus, there is a pronounced requirement on dragonflies to be able to select favorable winds, especially in autumn. In conclusion, a multi-generational, migratory circuit of the Indian Ocean by the globe skimmer is shown to be achievable, provided that advanced adaptations in physiological endurance, behavior and wind selection ability are present. Given that migration over the Indian Ocean would be heavily dependent on the assistance of favorable winds, occurring during a relatively narrow time window, the proposed flyway is potentially susceptible to disruption, if wind system patterns were to be affected by climatic change.

Varieties of visual navigation in insects

“…2 ). The North American common green darner dragonfly ( Anax junius ) makes similar seasonal journeys, travelling over multiple generations between wintering ranges around the Gulf of Mexico and their summer ranges in the northern U.S. and southern Canada (Hallworth et al 2018 ; Wikelski et al 2006 ), while the wandering glider dragonfly ( Pantala flavescens ) makes transoceanic journeys across the Indian Ocean, migrating between India and eastern Africa (Anderson 2009 ; Hedlund et al 2021 ).…”

Projected Effects of Climate Change on Species Range of Pantala flavescens, a Wandering Glider Dragonfly

“…It can also be found on many islands, but on some remote ones, such as Amsterdam Island in the middle of the Indian Ocean and Easter Island in the Pacific Ocean, it has apparently become a non-immigrant [34][35][36]. The nymphs of P. flavescens develop relatively quickly, taking about 40 to 60 days depending on the water temperature [37,38]. Generally, the optimum temperature for the growth and development of P. flavescens larvae was above 35 • C [32].…”

“…Global climate is increasing and shifting the habitat range of many species [16]. P. flavescens is an extraordinary migratory dragonfly that lives in tropical and temperate regions and migrates from the tropics to the temperate regions each spring [52], even crossing oceans [37]. For example, P. flavescens migrates from India across the Indian Ocean to East Africa in the fall, while the next generation returns from East Africa to India the following spring [37].…”

“…P. flavescens is an extraordinary migratory dragonfly that lives in tropical and temperate regions and migrates from the tropics to the temperate regions each spring [52], even crossing oceans [37]. For example, P. flavescens migrates from India across the Indian Ocean to East Africa in the fall, while the next generation returns from East Africa to India the following spring [37]. These suggest that dragonflies are able to choose favorable winds for migration, but if wind system patterns are affected by climate change, the proposed flight path may be disrupted.…”

Changing patterns of the East Asian monsoon drive shifts in migration and abundance of a globally important rice pest

“…Most insect migrants engage in windborne movements high above the ground, where their self-propelled flight speeds are considerably slower than typical windspeeds, and thus they are transported more-or-less downwind (Chapman et al, 2010(Chapman et al, , 2015Reynolds et al, 2017). With such transport on fast-moving airstreams, even minute insects can cover hundreds of kilometers in a single day or night of continuous flight, and thousands of kilometers over several successive days or nights of migration (Chapman et al, 2012;Florio et al, 2020;Gao et al, 2020;Hedlund et al, 2021;Huestis et al, 2019;Hu et al, 2019Hu et al, , 2021. In addition to the fundamental importance of winds, migration can be terminated by weather events such as heavy rainfall, downdrafts, and cold temperatures (Drake & Farrow, 1988;Drake & Reynolds, 2012;Wainwright et al, 2022;Westbrook & Isard, 1999); thus, meteorological factors have a critical influence on insect migration patterns (Chapman et al, 2015;Drake & Farrow, 1988;Reynolds et al, 2017).…”