What do the Maldives and dragonflies have in common?
Well, not a lot, seeing as how there is no surface water to speak of in the Maldives, and dragonflies need it in which to breed. Yet every year in October, Maldives resident and naturalist Charles Anderson started to take note of the fact that swarms of dragonflies were suddenly appearing, staying for a couple of months, then vanishing again just as quickly. At first he didn’t think too much of it, but when he started thinking about their fresh water dependence, he realised something strange was going on, so decided to investigate further.
Talking to colleagues in mainland India, he realised that the dragonflies – these are a specific species known as the Wandering Glider or Globe-Skimmer – weren’t just coming across to the Maldives to die, so something else must be going on. Spreading his net of informants a bit further afield, he started getting information that the dragonflies were being seen a few weeks later in East Africa, having travelled a couple of thousand kilometres across open ocean.
Incredibly, the Wandering Gliders were riding the front between the monsoon seasons, travelling at around 2000 metres in altitude, tracking the rains to East Africa where they would breed.
But the story (and the journey) didn’t end there…
Most mosquitoes have a larvae-dominant lifestyle; that is the larval or nymph period takes about 10-11 months (but can be up to four years!) and the adult stage only one or two months. The adults don’t have a lot of time in which to breed before they die.
In the case of the Wandering Glider however, things are quite different. Nymphs only have about six weeks to develop into adults, then they have to be up and off again, looking to breed, following the rains. From East Africa, they don’t go back to India though. The winds are against them by this time, and the dry season has settled in on the Asian sub-continent. Instead, the second generation of dragonflies continues south, following the winds, which are necessarily moving in towards the next rains, which are falling in Southern Africa.
Once in Southern Africa – hopefully we see a few of them at Londolozi this summer – another breeding bout takes place, and generation #3 emerges. By now the season is changing, and the population does a 180. They fly back north, retracing their steps to East Africa, where they breed yet again, and the fourth and final generation emerges for the flight back across the ocean back to India, where the cycle begins anew.
16 000 kilometres (10 000 miles) is the total distance flown in four generations of dragonfly over the course of a year; a truly remarkable migration! It was previously thought that the Monarch Butterfly undertook the longest migration of any insect (just under 10 000 km for the round-trip), but the Wandering Gliders wipe the floor with the Monarchs!
Riding the same air currents, and at similar altitudes, come a host of insectivorous migrational birds as well. Amur Falcons, European rollers and Blue-cheeked bee-eaters will all be flooding south, snacking on a number of dragonflies as they go.
We always make a big deal of bird migrations (which we should, as they’re pretty phenomenal as well) but I always used to try make them seem that much more hardcore by saying they didn’t have the benefit of the in-flight meal. Well, if they’re cruising along in the midst of a few million Wandering Gliders, maybe they do after all…
Birds, insane dragonflies, emerging dung beetles, impala lambs… the joys of summer are almost upon us. I just know that this year I’m going to be making a much bigger deal out of the Wandering Gliders than I have have before!