Sound localization in large mammals: localization of complex sounds by horses.

The research article investigates how horses identify the direction of sounds despite having large distances between their ears—an attribute among large mammals that is believed to enhance sound direction precision. Interestingly, the study finds that the horses’ ability to determine the direction of sound is significantly lower than other large mammals.

Study Background and Objectives

• The research is rooted in the notion that large mammals are able to localize sounds more accurately due to the large distance between their ears (interaural distance).
• This is believed to create broad binaural time and spectral differences, enhancing the mammal’s ability to identify the sound direction.
• Thus, the study aims to test this theory by determining the sound localization thresholds for horses and measuring the magnitude of the binaural cues available to them.

Research Method

• Sound localization thresholds for single clicks and 100-millisecond noise bursts were determined specifically for horses.
• The researchers then measured the magnitude of the binaural time and spectral cues for sound direction on a horse.

Key Findings

• Despite having relatively large interaural distances and broad binaural cues, horses displayed poor sound direction thresholds compared to other large mammals.
• On average, their thresholds were 22 degrees for noise and 30 degrees for clicks—significantly lower than expected.

Conclusion

• The research indicates that sound-localization accuracy is not solely determined by the physical availability of binaural cues.
• This suggests that other factors beyond ear distance could influence a species’ ability to localize sounds.