Hedgehogs Hear Ultrasound, Could Save Them From Traffic

A breakthrough discovery about hedgehog hearing could finally protect them from their biggest killer: traffic.

Scientists at Oxford University just confirmed that hedgehogs can hear ultrasound frequencies up to 85kHz, far beyond what humans or even dogs can detect. This surprising ability means engineers could design car-mounted devices that warn hedgehogs away from dangerous roads without bothering pets or people.

Vehicles kill an estimated one in three hedgehogs across Europe, driving a drastic decline in their population over recent decades. The gentle mammals freeze or curl into defensive balls when startled, making them especially vulnerable to passing cars.

Researchers tested 20 rehabilitated hedgehogs at Danish wildlife centers using tiny electrodes that measured brain responses to different sound frequencies. The hedgehogs responded to sounds between 4 and 85kHz, placing them in the ultrasound-hearing category alongside echolocating bats.

To understand how this works, scientists performed detailed CT scans of hedgehog ears. They discovered the animals have unusually small, dense middle-ear bones with a partly fused joint between the eardrum and ear bones, creating a stiff chain that efficiently transmits high-pitched sounds.

The Ripple Effect

Beyond saving hedgehogs from cars, this research could transform garden safety too. Lawn mowers and strimmers equipped with ultrasound signals could alert hedgehogs to move before the blades arrive, preventing another common cause of injury and death.

Dr. Sophie Lund Rasmussen, who led the study, is already seeking partners in the automotive industry to develop practical devices. Since hedgehogs hear much higher frequencies than dogs (who max out around 45kHz), designers can create repellers that protect wildlife without disturbing household pets.

The technology could work like existing deer whistles but tailored specifically for hedgehog hearing. As cars approach, ultrasound emitters would create an invisible barrier of sound, giving hedgehogs time to retreat to safety.

For a species facing population collapse, this simple solution addresses one of their most persistent threats with technology that already exists.