Editing Reindeer (section)

=== Clicking sound ===
The knees of many species and subspecies of reindeer are adapted to produce a clicking sound as they walk.<ref name=clicking>Banfield, Alexander William Francis (1966) "The caribou", pp. 25–28 in ''The Unbelievable Land''. Smith, I.N. (ed.) Ottawa: Queen's Press, cited in {{Cite journal
| pmid = 18986518
| year = 2008
| last1 = Bro-Jørgensen
| first1 = J.
| title = Knee-clicks and visual traits indicate fighting ability in eland antelopes: Multiple messages and back-up signals
| journal = BMC Biology
| volume = 6
| page = 47
| last2 = Dabelsteen
| first2 = T.
| doi = 10.1186/1741-7007-6-47
| pmc = 2596769
| doi-access = free
}}</ref> The sounds originate in the tendons of the knees and may be audible from several hundred meters away. The frequency of the knee-clicks is one of a range of signals that establish relative positions on a dominance scale among reindeer. "Specifically, loud knee-clicking is discovered to be an honest signal of body size, providing an exceptional example of the potential for non-vocal acoustic communication in mammals."<ref name=clicking/> The clicking sound made by reindeer as they walk is caused by small tendons slipping over bone protuberances (sesamoid bones) in their feet.<ref name="Shackleton2013">{{citation|title=Hoofed Mammals of British Columbia |first=David |last=Shackleton |date= May 2013 |publisher=Royal BC Museum |isbn=978-0-7726-6638-3 |orig-year=1999}}</ref><ref name="Banfield1966">{{citation|last=Banfield |first=Alexander William Francis|chapter=The caribou|title=The Unbelievable Land|editor-last=Smith|editor-first=I.N.|location=Ottawa|publisher=Queen's Press|year=1966|pages=25–28}}</ref> The sound is made when a reindeer is walking or running, occurring when the full weight of the foot is on the ground or just after it is relieved of the weight.<ref name="Dugmore1913" />