Could Ultrasound Technology Save Hedgehogs From Deadly Roads?

Scientists Discover Hedgehogs Hear Ultrasound — And It Could Save Their Lives

A groundbreaking study has revealed that hedgehogs possess the ability to hear ultrasonic frequencies far beyond the range of human hearing, opening the door to a potentially life-saving technology that could keep these beloved mammals safely away from roads and garden machinery.

The Road Traffic Crisis Facing Hedgehogs

Hedgehog populations across Europe have suffered a sharp and troubling decline over recent decades. A significant contributing factor is road traffic — with estimates suggesting that vehicles are responsible for killing as many as one in every three hedgehogs. Finding an effective, non-invasive deterrent has become a conservation priority, and this new research may finally offer a practical solution.

How the Study Was Conducted

Researchers from the University of Oxford, working alongside colleagues based in Denmark, tested the auditory capabilities of 20 hedgehogs that had been rehabilitated at Danish wildlife rescue centres. The team measured auditory brainstem responses by attaching small electrodes to the animals, which captured electrical activity passing between the inner ear and the brain as bursts of sound were played through a loudspeaker.

Published in the journal Biology Letters, the findings confirmed that hedgehog brainstems responded to sounds spanning a frequency range of 4 to 85kHz. This demonstrates a clear capacity to perceive ultrasound — defined as frequencies above 20kHz. To put this in perspective, humans can hear up to 20kHz, while dogs are capable of detecting sounds up to approximately 45kHz.

Unique Ear Anatomy Unlocked

The research team went a step further by conducting high-resolution micro-CT scans of a hedgehog's ear to construct a detailed, interactive 3D anatomical model. This revealed previously undocumented structural features that help explain the animal's impressive hearing range.

The scans showed that hedgehogs have exceptionally small, dense bones in the middle ear, along with a partially fused connection between the eardrum and the first of these bones. This structural arrangement stiffens the bone chain, making it highly efficient at transmitting high-pitched sound — a characteristic typically associated with echolocating bats and other mammals that rely on ultrasound to navigate and hunt.

A New Era of Hedgehog-Safe Technology

Armed with this knowledge, scientists believe it is now feasible to engineer devices that emit ultrasonic signals capable of deterring hedgehogs from hazardous environments. Potential applications include ultrasound repellers fitted to cars, as well as garden equipment such as lawn mowers and strimmers — all of which pose a serious risk to hedgehogs that often shelter in grass or roadside vegetation.

Importantly, because hedgehogs detect frequencies significantly higher than those audible to dogs, it should be possible to design repellers that do not disturb or distress household pets.

What Comes Next

Dr. Sophie Lund Rasmussen, the study's lead author and an assistant professor at the Wildlife Conservation Research Unit at both the University of Oxford and the University of Copenhagen, outlined the team's ambitions going forward.

"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," she said. "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."

With hedgehog numbers continuing to fall, the development of ultrasound-based deterrent technology could represent one of the most practical and scalable conservation tools to emerge in years.