Those who climb the mountains soon notice a curious detail: the flies seem less unleashed, almost clumsy. It is not an impression: At altitude the flies really react more slowly. To slow down it is the set of pungent cold, thin air and reduced oxygen. The frost stiffens the muscles making them fly more slowly, the rarer air of the mountain weakens the beat of the wings And the little oxygenation removes energy from their body. Visual perception is also affected by altitude, with consequences that explain why they become easier to catch.
The capture of flies and the climate in the mountains
We all know: it is colder in the mountains. In fact, in fact, the temperature drops quickly, On average of 6 ° C for each kilometer altitude. Going up from the valley floor up to 4000 meters the temperature drops clearly, a thermal leap similar to what it would meet by traveling for thousands of kilometers to the polar regions. For a fly, which depends on the external climate to regulate its metabolism, this cold represents a concrete challenge: at these temperatures, i muscles of the flies “stiffen”making sure that they move more slowly to one temperature of 18 ° C. In addition, chemical reactions that feed the flight to lose efficiency.
In high altitude the air is less dense
It is not just the cold that creates problems. The air, as you climb, not only cools down, but it also becomes less dense. At 4000 meters, in fact, the partial pressure is about half of the sea level. The wings must therefore perform a major work To generate the same lift. Some Alpine insects, such as bombs, have evolved wings and flight strategies that allow extraordinary performance even at altitudes higher than those of Everest. The common plains flies, however, they do not have these energy reserves and at high altitude they appear more clumsy.
The rarefied air makes oxygenation complicated
The flight requires ahuge amount of oxygen: In the few moments that separate rest from take -off, consumption can increase up to a hundred times. Already theoxygen at high altitude decreasesbut above all, with rarefied air, the diffusion of oxygen in the tissues becomes slower and the muscles cannot work at most. Experiments conducted on Drosophilaby Dillon and his team in 2006 of University of Washingtonshow that, in conditions similar to those of the great peaks, land flies walk more slowly And they often hesitate to take off. It is not inability, but a forced choice from the environment: in difficult conditions save energylimiting rapid movements.
Mosses in the mountains see and react with more slowness
Finally, the altitude also affects the sight of the flies, their main defense tool. They are able to perceive the movement of a hand that approaches in fractions of second, thanks to a very powerful visual system. But the quality of lightlow temperatures and stress they reduce speed with which this information is processed. Sensitivity to certain colors, such as blue, also varies according to the environment and temperature. At high altitude, the result is one less lightning reaction And one more margin for those who try to catch them.
