It has long been understood that power lines and electricity pylons are repellant to many species, but not why. Humans dislike them on aesthetic grounds, but unlike many other animals we cannot see UV light. Now it has “come to light” as it were, that many of the species on earth experience power lines are something utterly terrifying to them.
High voltage power cables, strung around the world on unwieldy scaffolds of strutting pylon towers, have become features of almost all landscapes. Whilst they are invasive, unavoidably ugly, and a obtruberance for historical film-makers they have become part of the status quo. To us. To many birds and animals they are something rather more ominous. They are barriers to ancient migration patterns and lines which cannot be crossed in the search for a mate. Why so?
According to a study published in Conservation Biology, it is all down to the flashes of ultraviolet light given out at irregular intervals by the lines themselves. These are intensified at the insulator points and represented as coronas along the lines. Ionised gases build up at certain points and these then emit the UV glow and throw off random flares as these gases dissipate. Power companies are aware of the phenomenon and do try to control it, as it symbolizes power leakage. However they cannot stop it from happening altogether. Helicopter mounted cameras monitor for such conduction problems, but even these have a low range of UV, much lower than the animals.
Combined teams from the universities of University College London (UCL), The Arctic University of Norway and University of Oslo in Norway,along with researchers from the Moorfields Eye Hospital in London, have collaborated on a paper citing avoidance of power lines as a source of fear for many species. The research was funded by the Biotechnology and Biological Sciences Research Council.
As one professor on the survey explained it, suspended cables are neither “a physical barrier” nor are they particularly associated with “human activity.” Even so, animals avoid them by distances of several kilometers. Glenn Jeffery from UCL has concluded that this avoidance is linked with animals “ability to detect ultraviolet flashing” and that they find this frightening. The higher the voltage, the wider the berth of avoidance occurs. This goes on for decades after the original installation.
This is having a detrimental effect on the security of natural territories. Fragmentation, cross-crossed by the power lines, is breaking up patterns of behaviour that are deeply ingrained. Reindeer are especially sensitive. In Norway, a herd of wild reindeer were followed to detect how they reacted to the power lines. Because their eyes pick up the flashes of ultraviolet emitted by high voltage electricity being transmitted, they experience this more acutely when it is dark. In snowy conditions, the flashes are then refracted around by bouncing off the white ground.
Many species, from birds to elephants, have the same enhanced vision, and will go out of their way to avoid power lines. While humans have become accustomed to them as inert and inevitable structures, most wildlife has not. The human eye can only see down to the blue-violet end of the color spectrum in a wavelength of light. (We,and the monkeys, are alone in this) Reindeer, by contrast, have reflectors at the back of their eyes. These have evolved to allow them to pick up UV light in the long dark winters, thus allowing them to search for plants to eat under the heavy snow cover. What looks to a human to be a grey and passive feature, to most animals is an alarming flashing and scary looking barrier. To reindeer, with their large irises, a power pylon is gleaming, bright, and eerily frightening.
From Africa to the Arctic 35 species have been found to be sensitive to UV radiation and are suffering the effects of the fragmentation of their natural habitat. In the Norway study, the 220,000 reindeer were established to have split up into 23 separate groups as a result of human infrastructure, which also includes roads.
This poses a real threat to biodiversity and “is a major global issue” says Dr Nick Tyler of the University of Tromso. Overhead power cables, he cites, are a “major and ubiquitous cause” of the loss and fragmentation of animal habitats. The avoidance of the power lines leads to interference with breeding, loss of grazing and interference with migration routes.
The many dozens of species found, through autopsy, to have eyes that can see UV, include red pandas, hedgehogs, dogs, cattle, okapi, bats, rats and cats. Worldwide, says Dr Tyler there are “hundreds of examples” of animals going out of their way to avoid power lines.
The previous theory as to the already noted avoidance patterns, was that corridors cut through forest to accommodate the installation and erection of electricity cables had affected animals such a reindeer, exposing them to predators. This explanation could not account for the reindeer of northern Norway who live on avast treeless tundra, herded by the Sami people.
Attempting to bury all existing power lines would be extremely unrealistic and wildly expensive. A more practical solution, suggests Glen Jeffery of UCL, would be to put non-conducting shield material around the cables. It is a responsibility that the power companies may eventually be forced to face up to.
Now that is is known that most mammals and birds see power lines as terrifying chains of flashing light, it is an explanation, at last, for their persistent avoidance of them.
By Kate Henderson