Shocking wildlife casualty levels from electric fences

Animals such as pangolins and tortoises that typically stay still, rather than flee, when sensing danger are among the many unintended casualties of the use of electric fences around wildlife areas, a study in African Journal of Wildlife Research found.

Researchers investigated data collected from the arid Kalahari region of South Africa, and considered why some species suffer more fatalities than others.

The use of electric fences around wildlife reserves and game farms where potentially dangerous animals roam are regulated in South Africa, to protect surrounding communities and their livestock from possible attacks. The fences are also used for personal security and to protect livestock against predators and theft.

Data for the studywas collected on a private game reserve in the Kalahari over a period of five years during which 108km of electrified fencing was patrolled three times a week. It showed that in five years, 43 vertebrate species collided 652 times with the main fence or tripwire. That amounted to one incident every 2 to 3 days. On average one animal died every 8.5 days - 213 animals in all. Most fatalities were among mid-sized animals, says zoologist, Darren Pietersen, who works for the non-profit Tikki Hywood Foundation, based in Zimbabwe. These included 40 steenbok, 28 Temminck's pangolins and 9 springbok. Larger-sized reptiles included 59 rock monitors and 28 serrated tent tortoises. Fifteen kori bustards , Africa's largest flying bird, also died. Almost all incidences involving reptiles, three out of every five (61,76%) birds, and one in every six cases (16,87%) involving mammals were fatal. The incident reports highlighted specific trends, says Pietersen. More fatalities occurred in summer, especially among reptiles. Mammals weighing more than 45 kilograms generally survived an electric shock, but anything smaller rarely did.

Mid-sized animals often became entangled in the fencing while trying to escape.

Pietersen says the number of deaths among pangolins and slow-moving tortoises reflects how these animals react to danger. “Unlike rabbits or antelope, they do not take flight when threatened. Pangolins curl up in a ball. Tortoises retract into their shells.”

Tortoises

An unpublished MSc thesis from the University of the Witwatersrand estimates that up to 30,000 tortoises die by electrocution in South Africa each year. Their size often counts against leopard tortoises in particular, says Sharon Holt, of South Africa's National Museum. At around 13 kilograms and with a shell standing at least 30cm off the ground, these bulky tortoises are the world's fourth largest.

Holt was lead author of a recent paper in the African Journal of Herpetology about the plight of leopard tortoises in central South Africa. It advocates for "more intensive regulation of electrified fences" because it is mostly bigger tortoises, already of breeding age, that are killed.

“Leopard tortoises take a long time to grow, with females only reaching sexual maturity at 15 years,” notes Holt. “Our models showed that high death rates amongst breeding size adults is likely to result in significant local population declines, even elevating extinction rates within several years.”

Pangolins

The IUCN's Pangolin Specialist Group describes electric fences as "a significant threat" that cause the death of between 2 and 13% of the South Africa Temminck's pangolin population annually. These percentages come from a chapter by Pietersen and others in The Red List of Mammals of South Africa, Swaziland and Lesotho.

His recent study in African Journal of Wildlife Research took Pietersen back to earlier work on the same Kalahari private game reserve where he, in the 2010s, saw his first fatally electrocuted Temminck's pangolin. He recalled how the animal was curled tightly around the lowest wire of an electrified wildlife fence. The 10-kilogram male was quite big compared to ones normally found in the Kalahari.

The sight of the dead orange-brown scaly mammal, the only pangolin species in Southern and Eastern Africa, moved him deeply, and led him to examine the impact of poorly designed electric fences on pangolins living in arid regions as part of his MSc degree at the University of Pretoria. In a subsequent paper in the South African Journal of Wildlife Research he listed electrocution as the No. 1 threat to vulnerable Temminck's pangolins in Southern Africa, ahead of the illegal or traditional medicine trade, habitat loss, road deaths or traps.

He now estimates that up to 2000 pangolins are killed on electric fences in South Africa each year, eclipsing the estimated 50 to 100 pangolins killed by poachers in the country. A pangolin which comes across a standard livestock or veterinary fence while roaming through its large home range in search of ants and termites is usually able to navigate across it successfully. Most try to find a weak point along the fence through which to force themselves, or scuttle over the lowest wire. Pangolins have even been known to climb fences as high as 2m. It's a different matter when a fence is electrified. Most South African provincial regulations indicate that the lowest such wires must be 10–20 cm above the ground, to deter predators. That's lower than most pangolins stand on all fours, says Pietersen, so they cannot duck underneath. Pangolins' strategy of curling up into a shielding ball of keratinous scales when threatened generally works against predators. But because these animals do not have protective scales on their stomachs, this defence strategy fails when they curl up around a high voltage wire in reaction to the shock of contact with an electrified fence.

In the absence of circuit breakers, the nocturnal animals become suspended in shock as the current flows through them. "If the continuous shocks do not kill them outright, exposure to the harsh sun does," Pietersen explains.

Towards solutions

Through his work for the Tikki Hywood Foundation, Pietersen helps to protect lesser known, smaller, endangered animals and works with other NGOs and willing fencing contractors to find practical solutions to curb the impact of electric fences.

"Easy things can be done to lessen the impact of electric fences, such as lifting the lowest electrified wire about 30cm from the ground," notes Pietersen. "Any electrified strand that is set too low, be it on the tripwire or the main fence, poses a threat to animals." He believes this modification can still keep larger predators within protected areas, but concedes that other solutions are needed for livestock farmers who worry about jackals. One option is better energisers - the device that provides pulsed charges to a fence.To this end, the Tikki Hywood Foundation, together with organisations such as Pangolin.Africa and fencing contractors are field testing a design which aims to allow animals of all sizes to extract themselves from a fence before being electrocuted - and without compromising the integrity of the fence itself. "Unfortunately this does not always work with pangolins when they wrap themselves around the fence wire. They only generate a very small amount of amps, which the energiser cannot pick up," says Murray Maclaughlin, project manager of Maclin Power Fencing, one of the companies involved in the field testing.

In mid-September the problem will be discussed along with the impact of power lines and roads at the 2nd virtual Global Congress for Linear Infrastructure and Environment (GCLIE). Its African-focused predecessor, ACLIE, first held in 2019, follows a week later in Kenya, from 18 to 21 September 2023.