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Box A2

Do You Hear What I Hear? Hearing and Sound in Animals
Erik Miller‐Klein

The capacity to hear sounds provides ani- the high frequency sounds associated with
mals with the ability to effectively monitor their vocalisations and physical size. In gen-
the activities and dangers in their environ- eral, most medium to large land animals have
ment usually outside the range of the other hearing that is equivalent to or greater than
senses. This hypersensitivity to the sounds humans’, so animals’ should be able to per-
around them means that zoo professionals ceive the human voice. The human vocal
should be acutely aware of the animal’s lis- range should not be a hurdle for communi-
tening abilities, and potential issues within cating and training zoo animals.
their captive environment. Hearing sensitiv- Animals with mobile pinna can signifi-
ity is measured with respect to sound’s range cantly change their sensitivity to the direc-
in amplitude and frequency, and can be tion of sound by adjusting the direction of
recorded through audiometric testing for a their ear. When loudspeakers were located in
representative sample of each species. An front of an animal, those animals with mobile
audiogram is a visual depiction of the sounds pinnae were able to optimally position their
which can be perceived, for example a human pinnae for detecting sound. For example
audiogram has been compared to a few reindeer could change their threshold of sen-
example animals, shown in Figure A2.1. sitivity by as much as 21 dB depending on
The audiograms in Figure A2.1 present the whether the reindeer’s pinnae were pointing
sensitivity of the ear to sounds with respect to towards or away from the sound source,
frequency. The lowest points on the graph are which is a 105% reduction in perceived sound
where the hearing of that species is the most (Flydal et al. 2001). Therefore it is important
sensitive, and where the line ends on the x‐ to watch the ears of the animal you are work-
axis is the frequency range limit for that spe- ing with, and training, to ensure their pinnae
cies. Research has shown that species are are faced towards you, otherwise your voice
most sensitive to the frequencies associated may not be perceptible above the other
with communication and survival. For exam- sounds that are distracting them.
ple, elephants can hear low frequency air- The function of the ear and pinna is only
borne sounds more efficiently than most one part of the challenging acoustic condi-
species (Herbst et al. 2012), as their inner ear tions of working with, and training, animals
lets them hear and communicate through low in captivity. One of the greatest challenges
frequency ground‐borne surface vibrations that is rarely discussed, but has the most sig-
(Reuter et al. 1998). Whilst the mouse has a nificant impact on the zoo professionals’
limited frequency range, it is most sensitive to ability to communicate with the animal is

Zoo Animal Learning and Training, First Edition. Edited by Vicky A. Melfi, Nicole R. Dorey, and Samantha J. Ward.
© 2020 John Wiley & Sons Ltd. Published 2020 by John Wiley & Sons Ltd.