It has long been assumed that reindeer´s avoidance of power lines in the tundra was due to their reluctance to make themselves vulnerable to predators by crossing the clear cuts made in the forest to accommodate the pylons. But why the Arctic populations, living in tree-free regions, would develop the same habit of staying clear of power lines was difficult to explain. A question made even more mysterious by the persistency of this behavior decades after the lines had been installed and significant human activity had ceased in the region.
The answer, this study finds, lies in the UV light that is emitted by power cables. Along high power lines, electric charges can build up in the cable and then be released into the air, generating a flash or corona of UV light; a well-known fact among power companies, who are partly addressing the issue in order to limit power leakage, but not enough to prevent the phenomenon all together.
UV light is invisible to the human eye, but most mammals can see it, as was revealed by a recent study. The reindeer´s highly sensitive vision, especially during the dark winter months, makes these flashes and corona appear particularly bright, which, together with the unpredictable pattern of flashes, makes it all the more hard for the animals to get accustomed to the phenomenon.
As a result, power lines, which run very long distances, can interfere with migration routes, breeding grounds and grazing for both mammals and birds, and contribute to loss and fragmentation of habitat, which constitutes the primary threat to biodiversity worldwide.
More on this study on webpages of The Guardian, The Independent, The Telegraph and the BBC.
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Picture: Reindeer herd in Finnmark, Northern Norway. © Lawrence Hislop