Why So Many Hedgehogs Die on Roads—and the Technology That Could Save Them

Across Europe, roads have quietly become one of the most dangerous places for hedgehogs. The small nocturnal mammal known as the European hedgehog (Erinaceus europaeus) is increasingly found dead along highways and rural roads, killed by passing vehicles. What might appear as scattered accidents has now been recognized by scientists as a significant conservation issue.

Scientific studies in recent years have confirmed that vehicle collisions are among the leading causes of death for hedgehogs in the wild. A study titled “Predicting hedgehog mortality risks on British roads using citizen science roadkill data”, published in the journal PeerJ in 2020, highlighted how road traffic significantly contributes to the decline of hedgehog populations in the United Kingdom.

The research was led by Patrick G. R. Wright, who analyzed thousands of roadkill reports submitted by citizen scientists across the UK. By mapping these records, the researchers were able to identify clear spatial patterns in hedgehog road mortality.

The study found that hedgehog deaths on roads are not random events. Collisions occur more frequently in suburban and rural areas where hedgehogs commonly roam in search of food and mates. Because these animals are primarily active at night, they often cross roads during periods when visibility is low and traffic remains steady.

Similar conclusions were reported in another study titled “Impacts and Potential Mitigation of Road Mortality for Hedgehogs”, published in the journal Animals in 2020. Led by L. J. Moore, the research identified traffic as one of the primary mortality factors affecting hedgehogs, alongside disease and predation.

Across Europe, the scale of the problem can be alarming. Several transport ecology analyses estimate that between 3 and 30 percent of local hedgehog populations may die each year due to vehicle collisions.

Researchers explain that the natural behavior of hedgehogs makes them particularly vulnerable to road traffic. These animals frequently cross roads while foraging or searching for mates. When threatened, hedgehogs typically curl into a tight defensive ball — an effective defense against predators such as foxes, but a fatal strategy when faced with a fast-moving car.

Hedgehogs Can Hear Ultrasound

While the growing number of road deaths has raised conservation concerns, recent scientific findings may offer a surprising opportunity for mitigation.

A study titled “Hearing and anatomy of the ear of the European hedgehog (Erinaceus europaeus)”, published in the journal Biology Letters in March 1, 2026, revealed that hedgehogs possess a much broader hearing range than previously understood.

The research was led by Sophie Lund Rasmussen from the University of Oxford in collaboration with an international team of scientists. The researchers tested the hearing abilities of hedgehogs using a method known as auditory brainstem response, which measures neural reactions to sound. They also conducted micro-CT scans to examine the internal structure of the animals’ ears.

Their findings showed that hedgehogs can detect sounds ranging from approximately 4 to 85 kilohertz. This range includes ultrasonic frequencies, which are far above the upper limit of human hearing.

The anatomical analysis of the hedgehog’s ear supported these results. The structure of the cochlea and the relatively lightweight middle ear bones appear well adapted for detecting high-frequency sounds.

According to Rasmussen, this discovery could open new pathways for protecting hedgehogs from traffic.

“Once we know that hedgehogs can hear ultrasound, it becomes possible to design technologies that warn them before vehicles approach,” Rasmussen explained.

Turning Biological Knowledge into Conservation Technology

The discovery of hedgehogs’ ultrasonic hearing ability has inspired scientists to explore a new approach to reducing road mortality, ultrasonic warning systems for vehicles.

The concept is straightforward. Vehicles could be equipped with devices that emit ultrasonic signals within a frequency range detectable by hedgehogs but inaudible to humans.

When a hedgehog hears this sound from a distance, the signal could act as an early warning, prompting the animal to move away from the road before a vehicle arrives. Researchers refer to this idea as an ultrasonic repeller, a device designed to deter animals using high-frequency sound.

If proven effective, such technology could potentially be installed not only in cars but also in garden equipment such as lawn mowers and strimmers, which are known to injure hedgehogs in urban gardens.

However, researchers emphasize that the concept remains at an early stage. Further studies are required to determine the most effective sound frequencies, the optimal detection distance, and whether hedgehogs consistently respond by avoiding the sound.

Still, the idea highlights how fundamental biological research can lead to innovative conservation strategies.

Why Hedgehogs Matter to Humans

The effort to protect hedgehogs often raises an important question, why should such a small animal matter to human life?

The answer lies in the ecological roles hedgehogs play within environments shared with people. Hedgehogs are active insect predators, feeding on beetles, caterpillars, slugs, and other invertebrates that can damage crops and garden plants.

By consuming these organisms, hedgehogs contribute to natural pest control, helping regulate insect populations in agricultural landscapes, gardens, and parks.

Hedgehogs are also an integral part of the food web. They function as predators of invertebrates while also serving as prey for larger animals such as foxes and birds of prey. Removing a species from this network can disrupt ecological balance.

In addition, hedgehog populations are often considered indicators of environmental health. Declines in their numbers may signal broader ecological problems such as habitat loss, excessive pesticide use, or increasing pressures from human infrastructure.

For these reasons, conserving hedgehogs is not simply about protecting a single species. It also reflects a broader effort to maintain healthy ecosystems that ultimately support human well-being.

As scientists continue to explore the sensory world of animals, new technologies may emerge that help reduce the unintended consequences of human development. And perhaps one day, a sound that humans will never hear could become a quiet safeguard for the hedgehogs crossing Europe’s roads at night. (Sulung Prasetyo)