Scientists at the University of Oxford have discovered something nobody knew about hedgehogs: they can hear ultrasound — sounds far beyond the range of human hearing. And now the researchers want to use that discovery to help save them.
The study, published in *Biology Letters* on March 11, 2026, found that European hedgehogs can detect sounds up to 85 kHz, with their strongest sensitivity around 40 kHz. Humans typically hear nothing above 20 kHz. The discovery opens a potential new tool for one of Britain and Europe's most beloved but quietly declining mammals.
**The Problem These Hedgehogs Face**
European hedgehog populations have been falling for decades. Road traffic is one of the leading causes: vehicle collisions kill an estimated one in three hedgehogs in some local areas. In 2024, the International Union for Conservation of Nature reclassified the European hedgehog as "near threatened" — a designation that reflects years of population decline.
Hedgehogs freeze when startled rather than fleeing — a behaviour that worked well against predators in the ancient past, but is devastating on a busy road.
**The Unexpected Discovery**
The research was led by Assistant Professor Sophie Lund Rasmussen from Oxford's Wildlife Conservation Research Unit. Her team measured the auditory brainstem responses of 20 rehabilitated hedgehogs from Danish wildlife rescue centres — essentially measuring the electrical signals in the brain as the hedgehogs responded to sounds at different frequencies.
The results were striking. Not only could the hedgehogs hear ultrasound, but their inner ear anatomy — revealed through high-resolution micro-CT scans — showed features specifically adapted for high-frequency sound processing, similar to the ears of echolocating bats.
> "Hedgehogs can hear high-frequency ultrasound, which suggests this ability may play an important role in their sensory world — and potentially in how we can protect them." > — University of Oxford, Wildlife Conservation Research Unit
Why hedgehogs evolved ultrasonic hearing isn't yet fully understood. The researchers are investigating whether they use it to communicate or to detect insects — their primary food source — in ways previously unrecognised.
**The Road Safety Application**
If hedgehogs respond to ultrasonic frequencies, it becomes theoretically possible to design devices that emit ultrasound in ways that deter them from crossing roads — or that signal the presence of an approaching vehicle before it reaches them.
Sophie Lund Rasmussen's team is now seeking to collaborate with car manufacturers to develop exactly this: ultrasonic sound repellents that could be fitted to vehicles, warning hedgehogs of their approach in a frequency the animals can actually detect.
If it works, the application would extend beyond roads. Garden strimmers and robotic lawnmowers also kill significant numbers of hedgehogs — smaller machines where ultrasonic devices might be even simpler to implement.
**What This Tells Us About Wildlife Sound**
The discovery reflects a broader pattern in animal sensory research: the animals around us have perceptual worlds that differ radically from our own. Bees see ultraviolet light. Elephants communicate through ground vibrations. Birds navigate by the Earth's magnetic field.
In each case, understanding the animal's sensory world opens entirely new possibilities for conservation — technologies that work with the animal's biology rather than against it.
Hedgehogs, it turns out, are listening to a frequency band we've never considered. The question now is whether we can use that knowledge to give them a better chance on our roads. 🦔💡
*Sources: Rasmussen, S.L. et al., Biology Letters (March 11, 2026). Royal Society. University of Oxford News. The Independent.*
