For a few weeks each year, roads around the world become amphibian death traps. According to the estimates of Germany’s Nature and Biodiversity Conservation Union, every year millions of amphibians die on German roads. In spring shortly after the thaw, frogs, toads and other amphibians set out to make the journey to their spawning grounds, driven by reproductive instinct. With limbs still stiff after the cold weather, these already sluggish creatures make slow progress. One of the main obstacles are the roads that amphibians often have to cross on the way, since the animals can’t dash across like we humans can. The results are fatal: according to NABU, current studies have shown that, even at a rate of 60 cars per hour, 90 percent of toads crossing the road will be run over. Despite the best efforts of committed nature conservationists, who pick the amphibians up to help them across the road, and careful drivers, the best solution for both people and the animals is to come up with a system that guides the amphibians safely beneath the roads.
"That’s why we’re building a test route at our outdoor testing site," explain Dr. Severin Seifert and Anna Renzl from the Fraunhofer Institute for Building Physics IBP. Together, the two IBP researchers from the Building Chemistry, Building Biology and Hygiene department are helping the company Ehlert Apparatebau GmbH to develop an innovative protection system for amphibians on the move. The project is being sponsored as part of the German Federal Ministry for Economic Affairs and Energy’s Central Innovation Program SME, using toads and common frogs from the Miesbach area in Bavaria in Germany to test individual components in spring 2015.
"Until now, the guide systems have mostly been constructed out of steel, plastic or concrete. The pros and cons of these materials has been the subject of sometimes controversial debate in expert circles. Opponents of steel, which heats up very quickly in the sun, point to the risk that animals could get stuck on the hot metal and burn," explains Seifert, a scientist from the group for Concrete Technology and Functional Construction Materials . Plastic, meanwhile, is not as stable or resistant, while concrete components have always been very heavy and difficult to handle. "By constructing components out of lightweight concrete, we want to develop an alternative that combines all the advantages of today’s amphibian guide systems as well as offering additional benefits." These concrete components are to be thin and extremely light while remaining highly durable, with a surface that offers amphibians the best possible guidance.
Dr. Severin Seifert and his colleagues at the concrete application laboratory are currently working on developing a special fine-grain lightweight concrete. To stabilize the concrete components, researchers intend to bolster them with textiles, and are currently looking for a suitable material. "Our main concern is that the material is suitable for the job and compatible with our special lightweight concrete mix – though of course we must always keep cost in mind," says Seifert. "Ultimately, we want the components to be affordable so that they can be used as widely as possible."
Anna Renzl from the Building Biology group is one of the scientists working on surface functionalization – with the aim of making sure that the surface of the components offers amphibians the best possible guidance. The thermal properties of concrete are already better for amphibians than plastic or steel. And since toads, frogs and other amphibians are cold-blooded animals, they prefer dark, warm and humid environments. Renzl intends to exploit this fact. "By treating the surface of the concrete with pigments, we want to optimize its properties so that these components become guide boards in the true sense of the word." In other words, when amphibians reach the embankment at the side of the road, the boards co-developed by Fraunhofer IBP will not only act as a barrier but also guide the animals to a tunnel leading beneath the road. "We know from experience that amphibians seek out darker, more humid environments, and we could turn this to our advantage in guide systems. If the color becomes darker nearer to the tunnel entrance, making the area increasingly warm and pleasant for amphibians, then the animals would automatically progress towards it," says the biologist. The surface structure can also be optimized so that the amphibians are not even tempted to try and climb up the sides of the guide barrier.
So that the Fraunhofer scientists can test their developments under realistic conditions, over the past months they have constructed a test route for the amphibians at Fraunhofer IBP’s outdoor testing site in Valley. Animal rights activists can rest easy, as the researchers have obtained a special dispensation from the government of Upper Bavaria to observe the animals on the new route and to see how they react to the customized surface. "We are also working alongside the
local nature conservation association
. Animals are handled with the greatest of care. And as soon as the observation is over, they are returned safely to their habitats – across the road, of course," assures Renzl. In other words, the tests are a far cry from crude animal testing. "The frogs and toads we will be using are the test pilots – or perhaps more accurately, test hoppers. They will make it clear if our developments work."
A few animals were able to make a test run during this year’s amphibian migration. Collected from the side of the road by workers from the Holzkirchen nature conservation association, the local toads and common frogs made a stopover at Fraunhofer IBP before being released at their desired destination. "We’re extremely grateful for local community support, as it’s an advantage to be able to work with native species. For all we know, amphibians bred in captivity or brought in from abroad might behave in a different way. If we want to develop the best possible guide system, we need to know how the animals native to Germany will react," explains the biologist. The test animals have an easy job: they only have to do what they always do. The test route comprises concrete blocks modified with various organic surface coatings. The Fraunhofer IBP researchers then observe how the animals react – whether the test subjects like the surface or not – and rate the various modifications according to their efficiency.
Testing will take place in the coming spring, when native amphibians make the journey to their breeding grounds following their period of hibernation. Until then, the researchers have time to work on their developments. "We would be delighted to be able to play our part in ensuring that fewer animals die on the roads during the migration period," say Renzl and Seifert. (ate)