The European hedgehogs (Erinaceus europaeus) are among the most emblematic animals of European fauna, but their populations are in decline. In 2024, the International Union for Conservation of Nature (IUCN) upgraded the species’ classification to “Near Threatened.”
Road casualties are one of the main causes of death for hedgehogs. It is estimated that each year up to 335,000 die from road traffic collisions in the United Kingdom and up to 340,000 in the Netherlands. In the 2023 Red Book of the Mammals of Mainland Portugal, it is pointed out that “the hedgehog is susceptible to roadkill on roads with some frequency, especially during the spring and summer, periods when they are more active.”
In the same publication it is stated that, for example, in Évora, an annual average of nearly three hedgehogs road-killed per kilometre is estimated, during a 12-year monitoring period. Although experts suggest that deaths from vehicle collisions may contribute to the species’ decline, “the impact of roadkills on the size of populations in Portugal remains unknown.”
Be that as it may, and although there are other threat factors, such as pollution, habitat destruction and the use of pesticides, roadkill is putting pressure on hedgehogs in several regions. Precisely to mitigate these impacts, a team of scientists studied the hearing of these small spiny mammals and concluded that using ultrasound on roads could reduce the number of animals run over.
In a paper recently published in the journal ‘Biology Letters’, they reveal that these animals can hear ultrasounds, something that was not yet clearly known.
“Having discovered that hedgehogs can hear ultrasounds, the next step will be to find partners in the automotive industry to finance and design sonic repellents for cars,” explains, in a statement, Sophie Lund Rasmussen, of the University of Oxford and the University of Copenhagen and the study’s first author.
“If future investigations show that it is possible to create an effective device to keep hedgehogs away from cars, this could have a significant impact on reducing the threat of road traffic to the species’ decline,” the study asserts.
The work involved testing the hearing of 20 hedgehogs at wildlife rehabilitation centres in Denmark, placing small electrodes on the animals to record electrical signals that travel from the inner ear to the brain. Based on the results obtained, it was confirmed that these mammals can hear sounds above 20 kilohertz, the minimum frequency of ultrasound, and up to 85 kilohertz.
The scientists are confident that it is possible to create ultrasound devices that deter hedgehogs from the roads, but that do not affect humans or other animals, such as dogs and cats. If these devices prove effective, they could be used not only to reduce deaths from road traffic, but also by lawn mowers and electric trimmers.
“It is especially exciting when a conservation-motivated investigation leads to a new fundamental discovery about the biology of a species, which in turn offers a new lifeline for conservation,” says David Macdonald, co-author of the study.
For the scientist, the “big question” now is to know whether hedgehogs respond to ultrasounds in a way that reduces the risks of collision with cars and other potentially deadly machines.
