Tortoises in the Karoo are under severe threat from the spread of electric fences which shock them, trap them and "cook them to death in their own shells". The 400,000km² of semi-desert in the heart of the country has the most diverse tortoise population in the world.But now they are "vulnerable to extinction" in a fast-changing habitat.Earlier this year, a national study by the Endangered Wildlife Trust found that wildlife ranching was on the rise, bringing with it an increase in fencing.story_article_left1Another study, by Andrew Beck at the University of the Witwatersrand, found that electric fences were gaining popularity not just among game ranch owners, but livestock farmers too.Beck found that 10 species of reptile were being killed by electric fencing, and 90% of them were tortoises.A survey on a farm near Graaff-Reinet found 14 dead tortoises in a single morning along 10km of fencing, and an earlier survey found that 52 tortoises had died over a short space of time along 8.4km of electric fencing in the Thomas Baines Nature Reserve."When tortoises come into contact with an electrified strand they usually react by retracting the head and limbs into the shell and thus remain a part of the circuit, receiving regular shocks, which ultimately results in death," Beck explained.Some of them urinate out of fear, allowing even more current to pass through their bodies.All three studies found that raising the lowest strands of the fences - currently 20cm from the ground - would stop them from being a death trap for tortoises and other small animals.Steve Smith, a conservationist with a special interest in the Karoo, said "no changes in design or regulations" had been implemented despite the findings.He described the many dead tortoises he had come across in the area.full_story_image_vleft1"They are all up against the live wire, the head is retracted, and the tortoise cooks to death inside its shell," he said.He called for the introduction of fencing regulations and enforcement by nature conservation authorities.The simplest solution would be a design change: all electric fences should be "35-45cm above ground".Sue Milton, an ecologist working on veld restoration in the Karoo, said some species of tortoises were "vulnerable to extinction" and that electric fences were an additional threat to tortoises on top of changes in land use, vehicle traffic, increases in crow numbers and reduction in vegetation cover.Fences with strands lower than 20cm from the ground killed tortoises, snakes, monitor lizards, aardvark, porcupines and other animals that tried to walk or dig under them.story_article_right2The more game farms and other fenced areas pop up, "the greater the mortality of vulnerable animals [like tortoises] will be".Milton said fences also restricted animal movements in times of drought, and could limit the search for mates, further fuelling the population decline.The solution was simple: "Placement of the bottom wire above 30cm [from the ground] would save so many animals."Adri Kitshoff-Botha, CEO of industry organisation Wildlife Ranching South Africa, said fences were necessary for demarcation and the benefits of game ranching far outweighed the risks."Most conservation of wildlife in this country takes place on private land where ownership has to be demarcated through the use of fences. Electric fences are used to keep damage-causing animals out," she said.The organisation was aware of the fact that "some reptilian species and other small animals like tortoises might suffer as a consequence of fencing [that has been] strung too low".But biodiversity on game ranches was rich, and the industry view was that "the overall contribution of private game ranching, which would obviously necessitate some form of fencing, far outweighs the negative consequences that results from fencing".Kitshoff-Botha said the organisation was drafting a code of best practice for electric fencing.farbert@sundaytimes.co.za..