Could ultrasound be the key to saving the European hedgehog from the brink of extinction? Researchers at the University of Oxford have unveiled pioneering findings that may transform conservation strategies for this beloved mammal. Their study, published today in Biology Letters, reveals for the first time that European hedgehogs possess the remarkable ability to detect high-frequency ultrasound, a discovery with profound implications for reducing roadkill and other hazards.
The European hedgehog (Erinaceus europaeus) is a treasured native species across much of Europe, yet it is currently facing a stark population decline. In a dramatic conservation turning point, the International Union for Conservation of Nature (IUCN) recently listed the species as “near threatened,” reflecting a worrying trend confirmed over the past decade. Among the leading threats to hedgehog survival are road traffic accidents, which studies estimate may be responsible for up to one in three deaths in local populations. This mortality rate underscores the urgent need for innovative interventions.
In seeking novel solutions, Assistant Professor Sophie Lund Rasmussen and her team from the University of Oxford and University of Copenhagen focused on the auditory capabilities of hedgehogs, an area that had remained largely unexplored. Previous assumptions about hedgehog hearing did not account for their potential sensitivity to ultrasound, a sound frequency range beyond the limits of human perception. Ultra-high-frequency sounds, traditionally associated with bats’ echolocation, had not been documented in hedgehogs until now.
To investigate, researchers conducted auditory brainstem response (ABR) testing on 20 rehabilitated hedgehogs brought from Danish wildlife rescue centers. This sophisticated neurophysiological technique involves placing tiny electrodes on the animals’ heads to measure electrical impulses traveling from the inner ear to the brain in response to sound stimuli. Testing spanned a broad frequency range from 4 kHz to 85 kHz, revealing that hedgehogs demonstrate peak sensitivity around 40 kHz, well within the ultrasonic spectrum.
The ability to hear ultrasound could open pathways to developing ultrasonic repeller devices, designed to emit high-frequency sounds perceived by hedgehogs but inaudible to humans and common pets. Such devices could potentially be integrated into roadside infrastructure or vehicular systems to deter hedgehogs from approaching dangerous zones, thereby mitigating the risk of fatal collisions. This innovation could revolutionize wildlife conservation by reducing anthropogenic mortality with non-invasive technology.
Complementing the neurological findings, the researchers employed micro-computed tomography (micro-CT) scanning on a deceased hedgehog specimen, facilitating an unprecedented 3D reconstruction of the animal’s ear anatomy. This analysis unveiled specialized structural adaptations—a small and dense constellation of middle ear bones, with a unique partial fusion between the eardrum and the malleus, the first bone in the ossicular chain. Such morphology enhances stiffness, critical for efficiently transmitting high-frequency sound vibrations.
Additionally, the study highlighted the presence of a particularly small stapes bone, the third ossicle, which interfaces with the fluid-filled cochlea within the inner ear. The stapes’ diminutive size reduces mass, allowing it to vibrate rapidly and sustain the transmission of ultrasonic frequencies. The cochlea itself was characterized as compact and relatively short, features conducive to processing rapid auditory signals. These anatomical traits parallel the adaptations seen in echolocating bats, underscoring the hedgehog’s auditory specialization.
Understanding these anatomical and neurological features broadens the scientific comprehension of how terrestrial mammals perceive their environments through sound. The implications extend beyond academic knowledge into tangible conservation applications. For instance, ultrasonic sound repellents could serve as a non-lethal method to steer hedgehogs away not only from roads but also from robotic lawnmowers and garden strimmers, devices increasingly implicated in unintentional wildlife harm.
The exciting potential of this technology calls for interdisciplinary collaboration. Professor Rasmussen emphasized the importance of partnering with automotive manufacturers and engineers to develop and refine effective ultrasound-based deterrents integrated directly into vehicles or roadside infrastructure. Such advancements could instigate a significant reduction in hedgehog road casualties, complementing broader conservation efforts aimed at stabilizing and eventually increasing populations.
Moreover, the discovery invites further scientific curiosity regarding the ecological functions of hedgehog ultrasound hearing. Do these animals utilize ultrasound communication among themselves? Is ultrasonic detection a mechanism for prey localization, perhaps enabling hedgehogs to identify insects or other small animals that produce ultrasonic cues? Ongoing investigations aim to unravel these behavioral and ecological questions, promising a richer understanding of hedgehog biology.
Professor David Macdonald, co-author and renowned conservationist, remarked on the serendipitous nature of this research. What began as a conservation-driven inquiry unearthed fundamental biological insights, which in turn propose innovative conservation solutions. The critical next phase involves testing behavioral responses to ultrasound in naturalistic settings to determine whether hedgehogs actively avoid these sounds, paving the way for practical deployment.
The collaborative nature of this study, involving experts from the University of Oxford, University of Copenhagen, Aarhus University, and associated veterinary clinics, exemplifies the power of international scientific partnerships. Together, they combine cutting-edge neurophysiology, imaging technology, and conservation biology to address pressing wildlife challenges. Their commitment extends to ethical considerations, as rehabilitated hedgehogs involved in experiments were carefully monitored and released unharmed.
Humans perceive sounds within the 20 Hz to 20 kHz frequency range, making ultrasonic sounds above 20 kHz imperceptible to us. Hedgehogs’ auditory sensitivity extends well into the ultrasonic domain up to 85 kHz, a range that not only surpasses human hearing but also that of common pets such as dogs and cats. This selective hearing range offers a unique avenue for targeted conservation interventions that minimize disturbance to other animals or humans.
As hedgehog populations continue to decline, urgent adoption of innovative solutions is essential. The application of ultrasonic technology represents a promising frontier, combining animal physiology insights with practical conservation engineering. By better understanding and harnessing the European hedgehog’s unique auditory capabilities, researchers hope to foster coexistence between humans and wildlife in increasingly urbanized landscapes.
This groundbreaking study offers hope: that the very sound frequencies beyond our own hearing could serve as a shield for hedgehogs against the growing threats they face. With continued research and development, ultrasound could emerge as a subtle but powerful guardian for one of Europe’s most cherished mammals.
Subject of Research: Hearing ability and ear anatomy of the European hedgehog in relation to conservation applications
Article Title: Hearing and anatomy of the ear of the European hedgehog Erinaceus europaeus
News Publication Date: March 11, 2026
Web References: http://dx.doi.org/10.1098/rsbl.2025.0535
Image Credits: European hedgehog. Credit: Tine Reinholt Jensen
Keywords: European hedgehog, ultrasound hearing, auditory brainstem response, ear anatomy, conservation technology, roadkill reduction, ultrasonic repellents, micro-CT scan, hedgehog population decline, Erinaceus europaeus
