Hedgehogs Have a Hidden Ultrasonic Ability That May Protect Them From Modern Dangers

The European hedgehog (Erinaceus europaeus) has a natural defense that has served it well for millennia: it rolls into a tight, spiny ball, protecting its vulnerable underbelly from predators. However, in the modern world, this biological shield has become a fatal weakness. While it works against traditional predators, it offers no protection against cars, robotic lawnmowers, and garden trimmers.

When threatened, hedgehogs often freeze or curl into a ball, a defense that offers little protection against cars and garden machinery and can lead to severe injuries. In some local populations, up to one in three hedgehogs die due to road accidents each year. Road mortality, along with habitat degradation, roads, urban development, and other human pressures, has contributed to the Western European hedgehog being reclassified as Near Threatened on the IUCN Red List in 2024.

But a March 2026 study led by researchers at the University of Oxford and published in Biology Letters found that European hedgehogs can hear high-frequency ultrasound, a discovery that could inform future conservation tools. Led by Assistant Professor Sophie Lund Rasmussen — affectionately known as “Dr. Hedgehog” — the team discovered that European hedgehogs can perceive high-frequency ultrasound.

A Hidden Hedgehog Superpower

Using non-invasive Auditory Brainstem Response (ABR) testing on 20 rehabilitated hedgehogs, researchers confirmed the animals can hear frequencies up to 85 kHz. Researchers say the next step is to test whether ultrasonic deterrents can be developed to encourage hedgehogs to move away from hazards such as roads, robotic lawnmowers, and garden strimmers before a collision occurs.

The study didn’t just confirm that hedgehogs can hear ultrasound — researchers also used high-resolution micro-CT scans to show how hedgehog bodies are built for it. Researchers created detailed 3D models of hedgehog ear bones to study the animals’ hearing. They identified middle- and inner-ear features consistent with high-frequency hearing beyond the limits of human hearing.

The team’s 3D modeling of hedgehog ear bones revealed a partly fused joint between the eardrum and the malleus (the first ear bone). This “stiffened chain” structure, common in ultrasound-sensitive animals like bats, allows high-pitched vibrations to pass efficiently through the animal’s middle ear.

Keys to High-Frequency Hearing

By mapping the hedgehog’s ear anatomy, researchers uncovered three specific features that enable their ultrasonic hearing.

First, the scans showed that hedgehogs have a very small stapes, the smallest middle-ear bone. Also known as the stirrup, this bone is extremely small, dense, and lightweight. Its unique structure allows it to vibrate fast enough to process frequencies up to 85 kHz.

Second, hedgehogs have a compact cochlea, or inner ear, which is short and tightly coiled. This design is specifically optimized to process rapid ultrasonic vibrations, unlike the low-pitched waves humans typically hear.

Third, hedgehogs have a peak auditory sensitivity at 40 kHz — far beyond the human limit of 20 kHz and nearly matching the 45 kHz range of dogs. This suggests there may be frequencies hedgehogs can detect that fall outside normal human hearing, which is why researchers think ultrasound could be useful in future deterrent systems.

These high-frequency adaptations likely evolved to detect the high-pitched sounds of insects, the hedgehog’s primary prey. They may also facilitate private ultrasonic communication between mothers and their young, hidden from the ears of larger predators.

Building Wildlife-Safe Technology

The discovery of the hedgehog’s hearing sensitivity provides a foundation for new safety standards in the automotive and gardening industries. Since their hearing sensitivity peaks well beyond the limits of humans and most pets, ultrasonic signals can serve as a silent but effective early warning system. Ultrasonic emitters on electric vehicles or robotic lawnmowers could warn hedgehogs of approaching equipment without disturbing humans or pets.

However, a primary concern for the research team is ensuring that such safety sounds remain effective over time. If an ultrasonic sound is played constantly, hedgehogs may become accustomed to it and eventually learn to ignore it. The study suggests triggering sounds only when a machine is in motion or near an animal. This targeted approach ensures the ultrasonic warning maintains its potency and prevents the hedgehogs from becoming desensitized. Researchers are also working to identify and refine specific ultrasonic patterns. Their goal is to find frequencies that consistently prompt hedgehogs to flee, overriding their instinct to curl into a “spiny ball.”

Developing hedgehog-safe technology requires a multidisciplinary approach. Dr. Rasmussen is currently seeking partners to fund and develop acoustic deterrents.

Understanding the Spiny Ball

This research doesn’t just save lives — it reshapes our understanding of hedgehog biology. Ongoing studies are exploring how hedgehogs might use ultrasonic whispers to communicate with their young or pinpoint tiny prey.

The next phase focuses on behavioral experiments to identify the specific ultrasonic patterns that reliably trigger a hedgehog’s flight response. This collaboration between the University of Oxford, the University of Southern Denmark, and the Natural History Museum of Denmark envisions a future where industry and science align. Integrating these insights can help the automotive and gardening sectors design technology that is both effective for humans and safe for the Near Threatened hedgehog.

This research helps to bridge the gap between anatomy, behavior, and engineering. By aligning these fields, we can move toward building a world where hedgehogs safely coexist with modern machinery. This ultrasonic “force field” may finally give these spiny survivors a real chance to thrive in an increasingly human-dominated world.