Every year, large numbers of insects make long-distance migrations during different times of the year. These displacements have been extensively studied from a group perspectivebut not individually, as the challenge of tracking these tiny organisms one by one is considerable.
Recently, a studying from the Max Planck Institute for Animal Behavior (MPI-AB) and the University of Konstanz focused on sphinxes of death (acherontia atropos), which get their name from the design on their back that looks like a human skull and that migrate to Europe periodically. The work reveals that these animals can maintain perfectly straight flight paths even in unfavorable wind conditions.
This behavior, detailed in the journal Science, indicates that the moths would have a sophisticated internal compass maintain beneficial migratory paths regardless of wind conditions, illustrating how insects travel long distances taking advantage of seasonal resources.
Specifically, when the winds were favorable, they flew high and slow, allowing the air to carry them. But during strong headwinds or crosswinds, they flew close to the ground and picked up speed to maintain the control your way.
“We are not sure about the implications of climate change for this species or if it would affect its orientation, but it has been shown that this occurs in other migratory animals, affecting the moment of their movement, for example”, he explains to SINC. Myles Menzfirst author of the study.
A windproof sail
The researchers tracked the insects by radio and planes by 80 kilometersthe longest insect monitoring distance in nature to date.
Moth caught in Col de Bretolet, a passage in the Swiss Alps through which many birds and insects migrate every year. / Christian Ziegler
Although migratory insects outnumber migratory birds or mammals, their journeys are the less understood form of displacement ranged animal
“Studying insects in motion is a formidable challenge,” says Menz, who conducted the research at MPI-AB and is now a professor at James Cook University (JCU) in Australia. “They are often too numerous to tag and find again, and too small to carry tracking devices.”
However, “acherontia atropos it is quite large, which makes it more suitable for carrying a transmitter and we can breed it in captivity”, he adds.
Much of what we know about the comings and goings of these tiny animals comes from studies that sample insects at a single moment, such as through radar or direct observation, which left large blank knowledge spaces: “Understanding what insects do during migration and how they respond to climate is the last frontier in this field,” says Menz.
Pioneering tracking in size and distance
acherontia atropos is a night migrant who travels up to 4,000 kilometers between Europe and Africa each year and who also has a considerable size (9 to 12 cm). Its proportions made it easy to implant 0.2 gram markers on its body. “Moths probably eat more weight than that in one night, so these tags are extremely light on insects,” says Menz.
Moths weigh up to 3.5 g, and the radio tags they carry weigh 0.2 g, less than 15% of adult body weight. / Christian Ziegler
The researchers followed fourteen moths for a maximum of four hours, which is already considered a migratory flight due to its duration. The insects traveled from Constanta to the Alps to pave the way for the Mediterranean and northwest Africa.
“For years, it was assumed that insect migration was mostly about being blown away by the wind. But here we show that they are capable of being great navigators, like birds, and they are much less vulnerable to wind conditions than we thought,” says Menz.
The next step in this field is to answer the question of how moths can keep these lines straight. The authors believe it is possible that insects are using internal compasses, both visual and magnetic, to plot your way around the world and reach your destination smoothly. “It would also be great to be able to study the entire migratory journey to find out where they winter,” concludes the JCU professor.
Reference:
Myles HM Menz et al. “Individual tracking reveals long-distance flight path control in a nightly migrating moth,” Science