Scientists uncovered the first physiological evidence that elephants' massive middle ears may enhance bone-conducted hearing, offering new insight into how these animals could detect low-frequency ground vibrations for long-distance communication.
Study: Bone-conduction hearing in elephants and humans: a middle-ear comparative study. Image credit: Wirestock Creators/Shutterstock.com
In a recent study published in Frontiers in Audiology and Otology, a research group from the United States (U.S.) characterized bone-conduction hearing in elephants by directly comparing the middle-ear mechanics of elephants to those of humans. The results offer the first detailed physiological evidence connecting elephant ear anatomy to the animals' capacity for detecting sound and vibration at low frequencies.
Elephant Ear Anatomy Favors Low-Frequency Hearing
Mammalian middle ears range from compact, high-frequency detecting ears in small rodents to larger, low-frequency-tuned anatomies in bigger animals. Elephants have the largest middle ears among terrestrial vertebrates, with unusually massive ossicles and a hearing range that extends to very low frequencies.
While their outer ear anatomy is known to enhance low-frequency airborne hearing, the role of bone conduction, which relies on ossicular and cochlear fluid inertia, remains unclear. Earlier experiments in human cadaver ears have demonstrated that adding mass to the ossicles alters vibration patterns and lowers the middle ear's resonant frequency, suggesting that elephants' massive ossicles may alter bone-conducted vibration.
Researchers Compared Elephant And Human Middle Ears
In the present study, the researchers obtained temporal bones from three elephants, one African and two Asian, donated post-mortem by sanctuaries and zoos, along with three human temporal bones from a hospital morgue.
Each bone was trimmed to fit a specimen holder, and the middle-ear cavity was accessed surgically to allow instrumentation while keeping the eardrum and ear canal intact. They then used a mechanical shaker to provide controlled bone-conduction stimulation directly to each bone, while a three-dimensional laser Doppler vibrometer tracked the resulting motion at reflective targets placed on the umbo, incus, stapes, and cochlear promontory.
Elephant specimens were stimulated with a series of pure tones spanning roughly 7 to 13,000 Hz, while human specimens were tested across approximately 17 to 11,000 Hz. The differential velocity metric was calculated to compare how much the ossicles moved relative to the inner-ear reference point across frequencies. Furthermore, the team determined the frequency at which vibration magnitude plateaued in each species, marking the middle ear's resonant frequency for bone conduction.
Statistical models incorporating frequency and species as predictors, along with random effects to account for repeated measurements within specimens, were used to test whether elephant and human responses differed significantly across low- and high-frequency ranges. Throughout testing, specimens were kept moist and refrigerated between sessions to preserve tissue integrity, with freeze-thaw cycles minimized wherever possible. Because the experiments were performed on post-mortem temporal bones, the study examined the mechanics of bone-conduction hearing rather than hearing behavior in living elephants.
Elephants Show Stronger Low-Frequency Bone Conduction
The study found that elephants and humans share some underlying patterns in bone-conduction hearing but differ substantially in the specific frequencies and magnitudes involved. The middle ear's resonant frequency for bone conduction was approximately 400 Hz in elephants, compared with about 1.2 kHz in humans, which was consistent with what was expected based on the much larger and heavier ossicles in the elephant’s ears.
Moreover, elephant stapes showed 3 to 4 times greater relative velocity than human stapes at frequencies lower than their respective resonant frequencies, suggesting that the added mass of elephant ossicles amplifies low-frequency vibration transmission. Unexpectedly, both species exhibited a plateau in vibration magnitude below roughly 200 Hz rather than a continued decline. The researchers suggested that pressure effects from the sealed ear canal used during testing likely contributed to this pattern rather than ossicular motion alone.
Moreover, the phase measurements suggested that vibration propagated through the ossicular chain in different directions in the two species. In humans, the motion appeared to originate near the stapes and travel toward the umbo, consistent with the response being driven by fluid inertia inside the cochlea. However, in elephants, the vibration seemed to move from the umbo toward the stapes. The authors noted that this may have been due to the cochlear fluid draining from the elephant specimens during repeated freezing and thawing.
Interestingly, the researchers also noted that elephants possess a skeletal muscle capable of closing the ear canal. They proposed that this mechanism could potentially boost low-frequency bone-conduction sensitivity by roughly 30 decibels, similar to the occlusion effect experienced by humans when the ear canal is blocked.
The researchers also found that both elephants and humans exhibited stronger low-frequency bone-conduction responses below about 200 Hz than previous models had predicted, suggesting that existing models may underestimate low-frequency bone conduction in both species.
However, the researchers acknowledged that the small number of specimens available for the study was a major limitation. Nonetheless, obtaining elephant temporal bones remains a challenge for such studies, and the authors also noted that the sealed ear canal and surgical preparation required for the experiments may have influenced the measurements, along with uncertainty about the condition of the cochlear fluid in the elephant samples.
Bone Conduction May Complement Airborne Hearing
In summary, these findings provided the first physiological evidence describing how bone conduction operates in the elephant middle ear. The results reveal a resonant frequency and vibration pattern that may be suited to low-frequency detection, suggesting that elephants may supplement their well-documented airborne hearing with bone-conducted sensitivity to ground-based vibrations.
Together, these mechanisms could potentially aid long-distance communication across the vast savanna landscapes that these animals inhabit, although the study provides physiological evidence from post-mortem specimens rather than direct evidence that living elephants use bone conduction during natural communication.
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Journal Reference
O'Connell-Rodwell CE, Berezin JL, Dharmarajan A, Pignatelli A, Chen R, Uzal F, Guan X and Puria S (2026). Bone-conduction hearing in elephants and humans: a middle-ear comparative study. Frontiers in Audiology and Otology. 4:1744613. DOI:10.3389/fauot.2026.1744613
https://www.frontiersin.org/journals/audiology-and-otology/articles/10.3389/fauot.2026.1744613/full
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