PP520 - What Is the Low-Frequency Range (Hz) of Hearing in African Elephants (Loxodonta africana)?

The African Elephant (Loxodonta africanas), spanning across all thirty-seven African countries, prowls the earth as the largest land mammal. Characterized with ears that are 'larger-than-life', elephants utilize their outer ear ("pinna") for both heat radiation and transduction of sound. Elephant hearing is largely dictated by their pinnae and internal anatomy. The Loxodonta africanas pinna spans approximately 1.0 by 0.5 m with a tympanic membrane that has an area of 103 mm2. Larger tympanic membranes and large Middle Ear spaces are structurally and physically optimal for a low-frequency hearing range (Garstang, 2004).

The purpose of this study was to determine the lowest-frequency (Hz) signal which can be detected by the African Elephant. The lowest perceived frequency can be determined through electrophysiological analysis and behavioral observation. Elephant audition and bioacoustics provides information regarding inter-species communication. Studies conducted by R.B. Martin found that elephants, even when separated by several kilometers, exhibited coordinated movements and moved directly toward each other in response to species-specific low-frequency vocalizations (1978). The production and interpretation of low-frequency signals is also involved in the ability of a male elephant to find a mature female elephant (Poole & Moss, 1981). 

The low-frequency (Hz) hearing range of the African Elephant (Loxodonta africanas) was assessed by using Brainstem Auditory Evoked Response (BAER) testing. BAER testing is a non-invasive evoked potential procedure which assesses the integrity of the auditory system. The response waveforms to broadband clicks were recorded at a rate of 0.40/s. Intensity was decreased until the Wave V responses lacked a repeatable latency (290-330 ms) and amplitude. This single-subject research study was conducted on a 45-year old female African Elephant over the period of one year. 

The data collection of this study will conclude on December 1st, 2022. The current results analyzed have averaged that the lowest frequency recorded with a repeatable Wave V using a Brainstem Auditory Evoked Response test is 3 Hz. There is limited research conducted previously on elephant audition. Further studies may be conducted to fully assess the hearing range of the African Elephant. Through a higher understanding of elephant audition, this provides greater context on the topic of elephant communication and signal detection. Additionally, it supports the growing field of Animal Audiology in its span of auditory research.