Researchers at the University of Oxford have found that European hedgehogs can detect ultrasonic sounds, potentially leading to devices that protect them from road traffic. The discovery, published on March 11 in Biology Letters, reveals adaptations in their ears for high-frequency hearing. This could help reduce hedgehog deaths from vehicles, a major threat to the near-threatened species.
The European hedgehog, a familiar wild mammal in Europe, faces declining populations partly due to road traffic, which kills up to one in three individuals in some areas. In 2024, the International Union for Conservation of Nature reclassified the species as "near threatened." New research shows these animals can hear sounds up to 85 kHz, including ultrasound above 20 kHz, with peak sensitivity at 40 kHz.
To test this, scientists measured auditory brainstem responses in 20 rehabilitated hedgehogs from Danish wildlife centers using electrodes and sound bursts from 4 to 85 kHz. The animals were checked by a veterinarian and released the next night. High-resolution micro CT scans of a deceased hedgehog's ear created a 3D model highlighting small, dense middle ear bones, a partially fused joint between the eardrum and first bone, a small stapes for rapid vibration, and a compact cochlea suited for ultrasonic processing.
Lead researcher Assistant Professor Sophie Lund Rasmussen, from the University of Oxford and University of Copenhagen, stated: "Having discovered that hedgehogs can hear in ultrasound, the next stage will be to find collaborators within the car industry to fund and design sound repellents for cars. If our future research shows that it proves possible to design an effective device to keep hedgehogs away from cars, this could have a significant impact in reducing the threat of road traffic to the declining European hedgehog."
The team suggests ultrasonic repellents could deter hedgehogs from roads, robotic lawnmowers, and garden strimmers, as humans hear up to 20 kHz and most pets less than hedgehogs. Dr. Rasmussen added: "Our novel results revealed that European hedgehogs are designed to, and can, perceive a broad ultrasonic range. A fascinating question now is whether they use ultrasound to communicate with each other, or to detect prey - something we have already begun investigating."
Co-author Professor David Macdonald remarked: "It is especially exciting when research motivated by conservation leads to a fundamental new discovery about a species biology which, full circle, in turn offers a new avenue for conservation. The critical question now is whether the hedgehogs respond to ultrasound in ways that might reduce the risks of collisions with robotic lawnmowers or even cars."
The study involved collaborators from the University of Oxford, Natural History Museum Denmark at University of Copenhagen, City Dyreklinik in Copenhagen, Aarhus University, Aarhus University Hospital, and the University of Southern Denmark. The findings appear in Biology Letters (2026; 22(3)), DOI: 10.1098/rsbl.2025.0535.
