Bat bridges erected across many major British roads to reduce roadkill are a waste of money because bats don’t like to use them, one of the UK’s leading experts has warned.
The bridges, which can cost hundreds of thousands of pounds, have been installed to help bats safely cross new highways despite evidence that they do not work, according to John Altringham, an ecologist at Leeds University.bats
“I’ve no idea who came up with this strange idea, nobody seems to admit to it now,” he told The Independent. “It seemed to me even before we did the science that no self-respecting bat was going to look at these strange things.”
Professor Altringham, who will this week submit a report to the Government on the issue, estimates that between 15,000 and 340,000 bats are killed on our roads every year.
He said road builders were continuing to use bat bridges – essentially poles on either side of the road with some wires strung between them – as a box-ticking exercise, even though they have proved ineffective. He said a “big industry” had grown up about the legal requirements designed to safeguard bats from traffic.
“When you want to build a road, you have to do bat surveys and spend money on these mitigation features. A significant amount of money is spent on it, but then nobody bothers to do any serious or accurate monitoring,” professor Altringham said.
Animals in decline
Animals in decline
1/8 Harbour seal (Phoca vitulina)
Where: Orkney Islands. What: Between 2001-2006, numbers in Orkney declined by 40 per cent. Why: epidemics of the phocine distemper virus are thought to have caused major declines, but the killing of seals in the Moray Firth to protect salmon farms may have an impact.
2/8 African lion (Panthera leo)
Where: Ghana. What: In Ghana’s Mole National Park, lion numbers have declined by more than 90 per cent in 40 years. Why: local conflicts are thought to have contributed to the slaughter of lions and are a worrying example of the status of the animal in Western and Central Africa.
3/8 Leatherback turtle (Dermochelys coriacea)
Where: Indonesia, Malaysia, Mexico, Costa Rica. What: Numbers are down in both the Atlantic and Pacific. It declined by 95 per cent between 1989-2002 in Costa Rica. Why: mainly due to them being caught as bycatch, but they’ve also been affected by local developments.
4/8 Wandering albatross (Diomedea exulans)
Where: South Atlantic. What: A rapid decline. One population, from Bird Island, South Georgia, declined by 50 per cent between 1972-2010, according to the British Antarctic Survey. Why: being caught in various commercial longline fisheries.
5/8 Saiga Antelope (Saiga tatarica)
Where: Kazakhstan, Mongolia, Russia, Turkmenistan, Uzbekistan. What: fall in populations has been dramatic. In the early 1990s numbers were over a million, but are now estimated to be around 50,000. Why: the break up of the former USSR led to uncontrolled hunting. Increased rural poverty means the species is hunted for its meat
6/8 Swordfish (Xiphias gladius)
Where: found worldwide in tropical, subtropical and temperate seas. Why: at risk from overfishing and as a target in recreational fishing. A significant number of swordfish are also caught by illegal driftnet fisheries in the Mediterranean
7/8 Argali Sheep (Ovis mammon)
Where: Central and Southern Asian mountains,usually at 3,000-5,000 metres altitude. Why: domesticated herds of sheep competing for grazing grounds. Over-hunting and poaching.
8/8 Humphead Wrasse (Cheilinus undulatus)
Where: the Indo-Pacific, from the Red Sea to South Africa and to the Tuamoto Islands (Polynesia), north to the Ryukyu Islands (south-west Japan), and south to New Caledonia. Why: Illegal, Unregulated and Unreported (IUU) fishing and trading of the species
“They are doing what they are obliged to do legally. There’s a lot of box-ticking you have to do. There are people who really don’t care whether it’s successful or not. I think that applies to a lot of the builders.”
In 2009, research showed that two bat bridges constructed across a bypass in Cornwall had cost about £27,000 for every bat that used them.
Professor Altringham said there was a “huge amount of uncertainty” about how many bats are killed in the UK. His estimate was calculated using research from the United States and Poland, but he said even if the true number was in the middle or towards the lower end of the range “it’s still a potentially significant mortality”.
The problem is caused by bats’ tendency to fly low to avoid predators when crossing open ground such as a road.
Professor Altringham’s research, which he will discuss at the Bat Conservation Trust’s Wildlife and Transport Infrastructure Symposium this month, suggests bats are more willing to fly under a road than use a bat bridge. In one case, 96 per cent of bats used an underpass, partly because it lay on a route they had traditionally used. Green bridges – effectively an area of countryside on top of the road – are another technique that, he said, was worthy of further study.
The Highways Agency defended the use of bat bridges as one strategy to reduce deaths. “We are legally bound to protect endangered species such as bats … and after considering all options we look at bat bridges. Our monitoring does show that these structures are used,” a spokesperson said. “However, we always look to see if there are further effective ways of protecting our endangered wildlife.”