Spike in numbers: Sounds good for hedgehog survival rates

Hedgehog numbers are falling all over Europe. But new research shows there’s a ray of hope for this ancient beast

You might expect that hedgehogs, rummaging for creepy-crawlies in leaf-litter, would have little use for high-pitched noise detection. But you’d be wrong! Picture: iStiock

The fox has many tricks. The hedgehog has but one. But that is the best of all. Ralph Waldo Emerson.

Hedgehog numbers are falling all over Europe. But now there’s a ray of hope for this ancient beast; new research suggests that its extraordinary acoustic ability might be harnessed to help rescue it.

Strike middle C on the piano and the string vibrates 262 times per second (262 Hz). The instrument’s top note rings at 4,186 Hz. Most young people can detect a 20,000 Hz sound. It’s just as well that we can’t hear anything higher-pitched than that; the powerful ultra-high pulses of echo-locating bats would be deafening. Did natural selection limit our hearing sensitivity so that we could talk to each other?

Dogs leave us in the halfpenny place when it comes to sound detection. Your canine pet responds to frequencies of up to 60,000 Hz. Cats, it’s claimed, hear 85,000 Hz noises and locate the sources of them. Felines hunt in the heart of darkness when hyper-sensitivity to sound is crucial.

You might expect that hedgehogs, rummaging for creepy-crawlies in leaf-litter, would have little use for high-pitched noise detection. But you’d be wrong! Twenty hedgehogs from Danish rescue centres were acoustically tested recently by Sophie Lund Rasmussen, the well-known ‘Doctor Hedgehog’, and a team from Oxford University. The hogs, the researchers discovered, detect frequencies of up to 85,000 Hz. Their sensitivity peaks at around 40,000 Hz.

Hedgehogs, mostly active at night, are not your typical stealth hunters. The slugs and snails they target can’t flee, so why did hedgehogs evolve ultra-sound detection abilities? In a paper just published, the authors suggest that noises have a role to play ‘in prey detection and communication’. Some creepy-crawlies are far from silent. The wide range of sensitivity to ultrasounds may be important for ‘directional hearing’.

'Near threatened'

That hedgehogs are sensitive to high-pitched sounds is a welcome finding. The European species is now classified by the International Union for the Conservation of Nature as ‘near threatened’. The main enemy is the motor vehicle; hedgehogs, trying to cross roads, are squashed to death under the wheels of cars.

Rolling into a prickly ball at the first sign of danger was a game-changer for hedgehogs back in Emerson’s day, but it has become a liability for their 21st Century descendants. Road traffic is estimated to kill one in every three of them.

‘These findings’, according to the researchers who carried out the recent tests, suggest that it might be possible to develop ‘ultrasonic repellents to mitigate traffic collisions and habitat disturbances’ and ‘conservation strategies for this declining species’.

A high-pitched sound-emitting device, attached to a vehicle, might warn hedgehogs of impending danger, without its noise disturbing people. But would it work?

I remember lifting a terrified curled-up hedgehog and moving it to safety away from the road. My car’s headlights must have warned the poor creature of danger. Would hedgehogs not respond to an acoustic warning in a similar fashion? And there are other wild creatures to consider; possible negative impacts on them would have to be taken into account. Further research is needed.

Sophie Rasmussen et al. Hearing and anatomy of the ear of the European hedgehog. Biology Letters. 2026.