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Territorial Scent Marking in Wild Silky Sifakas
By Erik R. Patel, Ph.D., DLC Post-Doctoral Project Director, SAVA Conservation
It was recognized early on in lemur research that amongst primates “prosimians stand
out for the wealth and variety of their olfactory communication” (Jolly 1966, p.132). At
least 11 different skin glands have been identified which may be used in prosimian
chemical communication in addition to bodily excretions such as urine, feces, and possibly
saliva (Schilling 1979). Other relevant physical adaptations include large olfactory bulbs (in
the brain), presence of a vomero-nasal organ, a large interior nasal region, and a wet nose
or moist rhinarium (Fleagle 1999).
Virtually all prosimians engage in scent marking behaviors in
which particular glands are rubbed against substrates (like tree
trunks), directly against conspecifics (“allomarking”), or where bodily
excrements (urine, feces, saliva) are deposited in particular ways at
particular locations. Well studied examples include throat or chest
marking of tree trunks by male sifakas (Mertl 1979; Lewis 2005;
Powzyk 2002), “stink-fighting” in male ring-tailed lemurs who anoint
their tails with shoulder and wrist gland secretions, and then waft
their odiferous tails at male opponents (Jolly 1966; Mertl 1979), and
urine-trail marking seen in all lorisine primates and many nocturnal
lemurs (aye aye, dwarf lemurs, mouse lemurs, giant mouse lemurs)
in which a trail of urine is laid by dragging the genitalia along a
substrate while releasing a small stream of urine. Across lemur
species, the most common type is anogenital scent marking which is
found in all diurnal and cathemeral species and many nocturnals
(Colquhoun 2011; Epple 1986).
Numerous functions of lemur scent marking have been identified
including genetic relatedness and genetic quality (Charpentier et al.
2010), estrus advertisement (Kappeler 1988, Scordato et al. 2007),
dominance or status signaling (Kappeler 1990), natal status (Pochron
et al. 2005), individual identity (Scordato et al. 2007) and
territoriality or resource defense (Mertl 1979; Mertl-Millhollen 1988,
2006; Irwin et al. 2004). The territorial resource defense function of
scent marking may be one of the earliest proposed functions, but for
some lemurs like eastern sifakas, very little is known. Eastern sifakas are considered
territorial animals but direct evidence for that is not readily available.
Western sifakas, such as Verreaux’s sifaka, are known to selectively scent mark the
periphery of their territory (particularly regions with adjacent groups) and mark at high
rates during intergroup encounters (Mertl 1979, Mertl-Millhollen 1988). However eastern
sifakas have much larger home range sizes (10 to 20 times larger depending on species/
site) and far fewer intergroup encounters which can influence the extent of perimeter
marking. Recent work in several tamarin species (new world monkeys) has both
challenged the territorial function of scent marking and offered various methodological
improvements such as controlling for ranging as well as size differences between home
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S A V A C O N S E R V A T I O N
Adult male silky sifaka with chest staining re-
sulting from chest scent marking.
Photo by Kevin Schafer