A 30m-wide mountain pass in the Pyrenees serves as a migration route for numerous insects, with up to 3,000 flies flying through a meter every minute.
(Video: Will Hawkes)
A team of experts from the University of Exeter, UK, has discovered that over 17 million insects migrate annually through Puerto de Bujaruelo, a 30m-wide gap in the Pyrenees along the border between France and Spain. The new study was published in the journal Proceedings of the Royal Society B Biological Sciences on June 11.
“It’s truly a wonder. You throw a net and find it filled with the smallest flies, all participating in this incredible mass migration,” said Will Hawkes, an expert at the Exeter Centre for Ecology and Conservation.
The new research stems from the findings of two British ornithologists, Elizabeth and David Lack, in 1950 when they encountered the migration through the Puerto de Bujaruelo pass at an altitude of 2,273m. “They witnessed a large number of hoverflies (Episyrphus balteatus) migrating across the mountains. We also went to that pass to see if the migration was still occurring and to document the species and their numbers,” Hawkes explained.
“Not only are large numbers of hoverflies still migrating through the pass, but there is much more. These insects begin their journey from a farther northern location in Europe, flying south to Spain and possibly even further in the winter. On some days, the number of flies can exceed 3,000 flying through a meter every minute,” he added.
Researchers capturing migrating flies in the Pyrenees.
In addition to hoverflies, the research team also observed cabbage white butterflies (Pieris rapae), dragonflies (Odonata), and houseflies (Musca domestica) passing through Puerto de Bujaruelo. The team utilized cameras, nets, and keen eyesight to detect and document various insect species.
Globally, insect populations are declining at an alarming rate, and it is likely that the number of insects migrating through the pass has also decreased since they were first observed 70 years ago. Scientists hope that these new findings could promote habitat protection for insects. “Insects are remarkably resilient and can recover quickly,” Hawkes noted.
The simultaneous movement of so many insects in the same direction is a wonder of nature, according to lead researcher Karl Wotton. “The combination of high mountains and wind patterns makes migration at high altitudes, which is often invisible, a rare sight that can be observed from the ground,” Wotton stated.
