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Making Sense of Scents: Olfactory Perception in Animals
Neil Jordan

Olfaction is the action or capacity of smelling the secretions of such specialised glands,
and is arguably the oldest form of communi- body orifices associated with digestion and
cation in nature. Olfaction underpins critical reproduction are also sources of scent signals
interactions as diverse as chemotaxis in sin- used in olfactory communication (e.g. Jordan
gle celled organisms (Vickers 2000), the pol- et al. 2013). Whilst chemical information
lination of flowering plants (Wright and may be excreted or secreted passively from
Schiestl 2009), and the nipple‐searching the bodies of animals as they move through
behaviour exhibited by newborn mammals their environment, animals often actively
(Hudson and Distel 1983). Whilst all forms of deposit olfactory signals into the environ-
communication involve the provision of ment using a diverse range of behaviours col-
information by a sender and the receipt and lectively called scent marking.
response to that information by a receiver As scent marks may be costly to produce
(Bradbury and Vehrencamp 1998), olfaction and supplies are limited (Gosling et al. 2000),
contrasts with other forms of communica- scent marks are adapted and released so as to
tion in that it does not require close proxim- maximise their longevity in the environment
ity between senders and receivers (Bradbury and the likelihood of their detection by target
and Vehrencamp 1998). This increases the receivers (e.g. Roberts and Lowen 1997).
breadth of contexts in which olfaction may Both chemical and behavioural adaptions
be employed and has profound effects on the may be employed to ensure that signals
design, distribution, and perception of olfac- remain in the environment for as long as pos-
tory signals and the anatomical equipment sible. For example, fatty acids are commonly
used in this process. found in scent secretions and are thought to
slow the release of signalling components
(Alberts 1992), a goal which may be further
Scent Production and promoted by the observation that animals
Distribution commonly place their scents in sites pro-
tected from the elements (Eisenberg and
Animals from ants to elephants are covered Kleiman 1972). Additionally species often
with an array of exocrine glands. These con- scent mark in prominent places, such as
gregations of sebaceous and apocrine tissues the crossroads of trails (Barja et al. 2004),
are often under the control of hormones, presumably to promote the discovery of sig-
which control the production and release of nals by intended receivers. The intended
chemical signals (Ebling 1977). In addition to recipients of these olfactory messages vary

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.