The ‘Landscape of Fear’ concept
Mammalian predators often do not to use their home range or territory
uniformly, and thus areas of high activity (core areas) would be
expected to be associated with a high density of kairomones and other
predatory chemical cues (Atkins et al. 2019). Prey individuals,
therefore, should avoid such areas and may be able to assess relative
predation risks in different areas (Atkins et al. 2019).
Conversely, the removal or reduction of predation risk may enable the
dispersal of prey populations; declines in Persian leopards
(Panthera pardus ) and African hunting dogs (Lycaon pictus )
allowed the recovery and distribution of Cape bushbuck
(Tragelaphus sylvaticus ) in Mozambique (Atkins et al.2019). Relationships such as these, however, have formed across multiple
generations of predator and prey species and, as such, alterations may
not result in observable ecological changes immediately; a 50 to 130
year absence of predators may result in the inability of prey to
identify recolonizing predators as a threat (Berger et al. 2001).
Such phenomena have given rise to the concept of a “landscape of fear”
(LOF), where prey may reduce their temporal and spatial exposure to core
predator areas in relation to perceived predation risk, although a
variety of other biological and evolutionary factors besides fear also
influence habitat use (Laundré et al. 2001; Laundré et al.2010; Bleicher 2017).
As a prerequisite for prey to actively avoid predation threats, it must
be possible to identify and associate predatory cues with predation risk
(Griffith 1920; Schaller 1974; Mech 1970: Table 1). In some cases, the
ability to identify scents specific to a predator species may be
advantageous; foraging beavers (Castor fiber ) show significantly
fewer defensive behaviours in response to the odours of dogs
(Canis familiaris ) compared to those of wolves (Canis
lupus ) (Rosell & Czech 2000); grey kangaroos (Marcopus
fuliginosis ) can discriminate the urine of coyotes (Canis
latrans ) from dingoes (Canis lupus dingo ) (Parsons et al.2007); mule deer (Odocoileus hemionus ) respond to the faecal
remnants of coyotes and mountain lion (Felis concolor ), but not
those of African lions (Panthera leo ), leopards, or tigers
(Panthera tigris ) (Mulller-Schwarze 1972). The type of kairomone
left by a predator is often species-specific; weasel (Mustela
nivalis ) tracks are rich in sulphur compounds, while those of beech
martens (Martes foina ) contain no sulphur-rich components
(Schildknecht & Birkner 1983; Apfelbach et al. 2015). The
ability to detect kairomones also differs between prey species; the
abundance of trace amine-associated receptors (TAARs), a group of
olfactory receptors used to detect kairomone presence, differs between
prey species (Borowsky et al. 2001; Ferrero et al. 2011).
Rodents may possess up to seventeen TAARs, while primates only six
(Borowsky et al. 2001; Ferrero et al. 2011). The ability
to differentiate between predatory threats and benign, albeit from
closely related predators, chemical cues may reduce the energetic
expenditure spent on vigilance and evasion.
Furthermore, the extent of predation risk likely varies, and prey
species should possess the ability to distinguish between the least
threatening and more ominous indicators. These abilities are often
demonstrated in the occurrence of “giving up distributions” (GUDs),
with the emphasis on whether prey animals sacrifice foraging behaviour
in relation to the perceived risk of predation (Brown 1988; Brownet al. 1994; Laundré et al. 2001). For instance, moose
(Alces alces ) quit more than half of experimental areas following
repeated exposure to urine from wolf and grizzly bears (Ursus
arctos ) (Pyare & Berger 2003). More specifically, a forager should
terminate feeding in a food patch when the value of its harvest rate (H)
no longer exceeds the sum of the energetic cost of foraging (C),
predation risk (P) and missed opportunity cost (MOC): H=C+P+MOC (Brown
1988), and has been shown to apply in a range of taxa under varying
ecological conditions (Stokes et al. 2004; Merwe & Brown 2008;
Shrader et al. 2008; Valeix et al. 2009; Iribarren &
Kotler 2012; Clinchy et al. 2013; Gallagher et al. 2017).