Introduction to Exceptional Hearing
Bats possess some of the most advanced hearing systems in the animal kingdom. As they navigate through the night sky, these remarkable creatures emit high-frequency calls and listen intently for the returning echoes to find their way in the dark. While the bat’s calls may be inaudible to many animals, the greater wax moth can detect frequencies as high as 300 kilohertz, which is roughly 15 times more than what humans can hear. By perceiving the bat’s call, the moth is alerted to danger and manages to evade its predator just in time.
Both bats and greater wax moths are often highlighted for their impressive auditory capabilities, sparking the question: which animals truly possess the best hearing?
“What is ‘best’ is always relative,” said Christine Köppl, a professor of cochlear and auditory brainstem physiology at the University of Oldenburg in Germany. “Sensitivity, the ability to distinguish between similar sounds, and the ability to localize sounds are all different factors that create an animal’s sense of hearing,” she stated in an email to Live Science. The complexity of these factors complicates any efforts to rank hearing abilities, yet certain species stand out.
Owls: Masters of Prey Detection
Among animal auditory systems, Christine Köppl expresses particular admiration for barn owls (Tyto alba). “I have worked on barn owls, so they are on top of my list,” she noted. Their entire auditory system has evolved to enhance their nocturnal hunting skills, allowing them to accurately locate prey by sound.
Owls utilize their acute hearing to complement their vision, especially in low-light conditions. They can detect even the slightest movements of a mouse beneath layers of snow or leaves. This capability is attributed to a few key adaptations:
- The facial feathers of barn owls form a dish shape that channels sound directly into their ears.
- Their right and left ears are positioned at slightly different heights, which helps them discern the precise location of sound by detecting minute differences in timing.
Echolocators: Bats and Dolphins
Bats and dolphins, despite their vastly different habitats, both exhibit the remarkable ability to echolocate.
“I love dolphin and bat ears, because they’re not simply picking up sound and processing it, but they’re using it for active imaging of their environments,” stated Darlene Ketten, a research scholar emeritus at Woods Hole Oceanographic Institution.
Echolocation involves emitting sounds that bounce off surrounding objects, with the returning echoes providing critical information about the environment. According to Ketten, dolphins and some bat species create intricate mental maps using sound, surpassing human-made sonar technology.
Bats are equipped with features that enhance their echolocation:
- They possess large outer ears that are adept at collecting sound waves.
- Their brains contain substantial auditory processing centers, akin to the significant visual processing areas in humans.
Dolphins also rely on powerful auditory systems; their auditory nerve is about two to three times thicker than that of many terrestrial mammals. However, their ears differ from those of land animals. Dolphins’ external ear openings are merely small holes, and they likely use fat deposits around their jaws to sense sound waves in water.
Unique mechanisms in their ears help both bat and dolphin species eliminate interference from their own echolocation calls, allowing clear perception of their surroundings.
Pinnipeds: The Dual-Environment Experts
Brandon Southall, president and senior scientist for Southall Environmental Associates, champions the often-overlooked pinnipeds—seals, walruses, and sea lions—for the title of best hearing.
“They do the nearly impossible thing of having to hear both above and below the water,” Southall remarked.
Each species is adapted to its specific acoustic environment. When humans submerge their heads underwater, sound becomes muffled, as our ears are optimized for air. Pinnipeds, however, function in both land and aquatic environments, needing to excel in hearing in both mediums.
“If you take a dolphin and you put it in air, it’s virtually deaf and has no directionality,” Southall explained.
Interestingly, some pinnipeds can hear almost as well as owls on land and at comparable levels to dolphins underwater. Southall has even documented seals reacting to the sound of crunching snow from a distance of up to 1 mile (1.6 kilometers).
Their unique adaptation involves filling the middle ears with blood while submerged, which allows sound waves in water to travel with minimal distortion. Upon returning to land, the ears refill with air, enabling them to detect sounds traveling through the air.
“It’s mind-blowing,” Southall concluded.
