Hedgehogs can hear high-frequency ultrasound, which could help keep them safe from cars. Scientists hope to use ultrasound repellers to deter hedgehogs from roads.
Cars kill up to one in three hedgehogs. This is a major reason for their population decline across Europe.
How Scientists Discovered Hedgehog Hearing
Researchers from the University of Oxford and Denmark studied 20 hedgehogs. These hedgehogs were being cared for in Danish wildlife rescue centers.
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Start Your News DetoxScientists placed small electrodes on the hedgehogs. These electrodes recorded electrical signals between the inner ear and the brain. They played short bursts of sounds through a loudspeaker.
The electrodes showed that the hedgehog's brainstem reacted to sounds from 4 to 85 kHz. This means hedgehogs can hear very high frequencies, including ultrasound (above 20 kHz). For comparison, humans can only hear up to 20 kHz, and dogs up to 45 kHz.
The study was published in Biology Letters.
Unique Ear Structure
Researchers also used micro-CT scans on a dead hedgehog. They created a 3D model of its ear. This model revealed new details about hedgehog ears.
Hedgehogs have very small, dense middle-ear bones. They also have a partly fused joint between the eardrum and the first bone. This makes the chain of bones stiffer. This stiffness helps them hear high-pitched sounds efficiently. These features are common in mammals like bats, which use ultrasound to find prey.
Future Solutions
These findings could lead to new designs for garden tools and vehicles. Ultrasound repellers could keep hedgehogs away from dangerous areas. Since hedgehogs hear higher frequencies than pets like dogs, these repellers could be designed not to bother pets.
Dr. Sophie Lund Rasmussen, the lead researcher, is an assistant professor at the Wildlife Conservation Research Unit at the University of Oxford and University of Copenhagen. She hopes to work with the car industry to develop sound repellents for cars. If these devices prove effective, they could greatly reduce hedgehog road deaths.
Deep Dive & References
Hedgehogs hear high-frequency ultrasound - Biology Letters, 2025
