The European hedgehog, a beloved wild mammal across Europe, is facing a troubling decline, with the International Union for Conservation of Nature designating it as "near threatened" in 2024. A significant factor contributing to this decline is road traffic, which is believed to result in the deaths of up to one-third of hedgehogs in certain populations due to vehicle collisions.
Recent research has uncovered that hedgehogs possess the ability to hear ultrasonic frequencies, opening up new possibilities for their protection. This discovery suggests that ultrasonic sound repellents could be developed to deter hedgehogs from dangerous areas like roads. Previously, scientists were uncertain whether hedgehogs could detect sounds in this high-frequency range.
Lead researcher, Assistant Professor Sophie Lund Rasmussen from the Wildlife Conservation Research Unit at the University of Oxford and the University of Copenhagen, stated, "Now that we know hedgehogs can perceive ultrasound, our next step is to collaborate with the automotive industry to create sound repellents for vehicles. If our future studies demonstrate that we can effectively design a device to keep hedgehogs safe from cars, it could significantly mitigate the risks posed by traffic."
Exploring Hedgehog Hearing
To assess the hearing capabilities of hedgehogs, researchers conducted experiments involving 20 rehabilitated hedgehogs from Danish wildlife rescue centers. By measuring their auditory brainstem response, the team could track electrical activity from the inner ear to the brain while exposing the animals to various sound frequencies.
The results indicated that hedgehogs can detect sounds between 4-85 kHz, with heightened sensitivity around 40 kHz, confirming their ability to hear ultrasonic sounds, which begin at frequencies above 20 kHz. Following the tests, the hedgehogs were checked by veterinarians and safely returned to their natural habitats.
Innovative Ear Structure
In addition to behavioral studies, researchers employed high-resolution micro CT scans to analyze the ear structure of a hedgehog that had been euthanized due to injury. This investigation led to the creation of a detailed 3D model of the hedgehog's ear, revealing unique features that enhance its ability to hear high-frequency sounds.
The scans indicated that hedgehogs have small, dense bones in their middle ear, which are adapted to transmit high-pitched sounds effectively. The structure of the stapes, the smallest bone in the middle ear, allows for rapid vibrations, enhancing the hedgehog's capacity to process ultrasonic frequencies.
Potential for Ultrasonic Repellents
These findings pave the way for the development of ultrasonic repellents that could be audible to hedgehogs while remaining inaudible to humans and pets. If subsequent research confirms the efficacy of these devices, they could play a crucial role in safeguarding hedgehogs from road hazards and other dangers, such as robotic lawnmowers.
Dr. Rasmussen expressed enthusiasm about the implications of their findings, noting, "Our research has revealed that European hedgehogs are equipped to perceive a wide range of ultrasonic frequencies. We are now investigating whether they utilize ultrasound for communication or prey detection." Co-author Professor David Macdonald emphasized the significance of this discovery, stating that conservation-driven research can lead to fundamental insights into species biology, ultimately fostering new conservation strategies.
