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Current Zoology
60 (1): 16–25, 2014
Antipredator deception in terrestrial vertebrates
Tim CARO*
Department of Wildlife, Fish and Conservation Biology, and Center of Population Biology, University of California, Davis, CA
95616, USA
Abstract Deceptive antipredator defense mechanisms fall into three categories: depriving predators of knowledge of prey’s
presence, providing cues that deceive predators about prey handling, and dishonest signaling. Deceptive defenses in terrestrial
vertebrates include aspects of crypsis such as background matching and countershading, visual and acoustic Batesian mimicry,
active defenses that make animals seem more difficult to handle such as increase in apparent size and threats, feigning injury and
death, distractive behaviours, and aspects of flight. After reviewing these defenses, I attempt a preliminary evaluation of which
aspects of antipredator deception are most widespread in amphibians, reptiles, mammals and birds [Current Zoology 60 (1): 16
25, 2014].
Keywords
1
Amphibians, Birds, Defenses, Dishonesty, Mammals, Prey, Reptiles
Introduction
In this paper I review forms of deceptive antipredator
defenses in terrestrial vertebrates, a topic that has been
largely ignored for 25 years (Pough, 1988). I limit my
scope to terrestrial organisms because lighting conditions in water are different from those in the air and
antipredator strategies often differ in the two environments. I define antipredator deception as a behavioural
or morphological trait that reduces the profitability of a
predatory attempt through dishonesty by obscuring the
presence of an animal, increasing its apparent handling
time, or lowering the apparent benefits of consumption.
Antipredator deception can occur by means of (i) depriving the predator of information, (ii) by providing
cues and (iii) through signals and all are seen in vertebrates. Most examples of crypsis, be they principally
morphological as in background matching, behavioural
as in remaining still, or both are selected so as to prevent the predator detecting the presence of prey in the
environment. Cues (which are generated inadvertently
for purposes other than communication [Bradbury and
Vehrencamp, 2011]) may be honest markers of unprofitability or dishonest markers in that they increase apparent handling time of an otherwise profitable prey
item. For example, body inflation in anurans may make
gripping prey more difficult or it may fool the predator
into assessing the prey is too large to handle (Toledo et
al., 2011). Similarly, a rapid change in flight path in
Received Sep. 9, 2013; accepted Dec. 10, 2013.
 Corresponding author. E-mail: [email protected]
© 2014 Current Zoology
homeotherms may increase the distance between prey
and the pursuing predator or dupe the predator about the
flight path trajectory, or both (FitzGibbon, 1990).
Last, an antipredator defense may be a dishonest
signal. Bradbury and Vehrencamp (2011) state that “true
deception occurs when a sender produces a signal
whose reception will benefit it at the expense of the
receiver regardless of the condition with which the signal is supposed to be correlated” (see also Maynard
Smith and Harper, 2004). Examples of Batesian mimicry or death feigning fall into this category. These have
been selected to make the predator respond in a way
that benefits the signaler but not the receiver.
Unfortunately, it is often problematic to demonstrate
dishonesty because the trait may be honest but imperfect or incomplete (Endler, 1978). For instance, a bluff
charge might be deceitful or simply a charge that failed
to be carried through raising the issue of intent which is
difficult to investigate operationally. In addition, a signal may be honest to a small predator but dishonest to a
large one. Empirical data and sensory and economic
analyses are required to tease apart these possibilities
yet none exist for vertebrates. Therefore many of the
putative cases of antipredator deception listed below,
broadly in predatory sequence, are difficult to attribute
unequivocally as dishonest because convincing data on
their beneficial consequences for prey, and the mechanisms by which they are achieved, are lacking even in
these well known taxa.
CARO T: Antipredator deception
2
Crypsis: Depriving the Predator of
Information
2.1 Background matching
Crypsis is a range of strategies that prevents detection (Stevens and Merilaita, 2009) and is therefore a
type of deception in that the colour, morphology and
behaviour of an individual make it difficult to distinguish from the background (Diamond and Bond, 2013).
I concur with Ruxton (2011) that a cryptic organism has
an impact on the sensory system of the receiver such
that if the organism was removed, the flow of information would change. This distinguishes crypsis from hiding. Crypsis occurs by means of several mechanisms
only some of which are found in terrestrial vertebrates
(Edmunds, 1974; Ruxton et al., 2004). The principal
one is background matching, where the appearance of
the animal generally matches the colour, lightness and
pattern of one (specialist) or several (compromise)
background types (Stevens and Merilaita, 2011). The
most famous example of background matching is of
industrial melanism in the peppered moth Biston betularia (Kettlewell, 1973). In mammals, comparative
studies reveal that patterns of colouration in species of
artiodactyls (Stoner et al. 2003a), carnivores (Ortolani
and Caro, 1996; Allen et al., 2011), lagomorphs (Stoner
et al., 2003b), cetaceans (Caro et al., 2011) and pinnipeds (Caro et al., 2012) often resemble the general
colour features of their habitat suggesting that predators
(generally) are being deceived about the presence of
prey in the environment. Within species, experiments
with different coloured plasticine Peromyscus mice
show that there is strong selection by predators for prey
to match the background closely (Vignieri et al., 2010).
In birds, females are often drab compared to males,
and it has long been thought that female ground nesting
species need to be brown or speckled to avoid being
detected while incubating their eggs (Wallace, 1868;
Soler and Moreno, 2012). In addition, speckled egg
colouration is thought to be an adaptation to avoid detection by predators (Kilner, 2006) especially in open
nesting passerines (Westmoreland and Kiltie 1996; but
see Cherry and Gosler, 2010). In quail Coturnix japonica, eggs of different hue may be laid on the types of
substrate that make them optimally camouflaged (Lovell et al., 2013).
Remarkable resemblances are found between lizards
and snakes and their backgrounds (Cooper, 2012; Farallo and Forstner, 2012; Isaac and Gregory, 2013).
Across snakes, blotched patterns are seen in large, slow
17
ambush-hunting species, spots are found on species
residing near cover, and small speckled patterns are
found on habitat generalists (Allen et al., 2013). Testudines and crocodilians have dark and mottled shells and
skins that appear to match their aquatic environment
(Norris and Lowe, 1964; Greene, 1988). Anuran and
salamander species appear to match leaf litter, pond and
river vegetation using uniform or mottled colouration to
avoid detection by predators (e.g., Hoffman and Blouin,
2000; Cooper et al., 2008; Eastman et al., 2009). For
example, lighter Ambysoma barbouri salamander larvae
have higher survival than darker larvae in fish filled
streams (Storfer et al., 1999). As an aside, glass frogs
(Centrolenidae) have transparent ventra which might
possibly help to blend in with the background and avoid
detection (Rudh and Qvarnstrom, 2013).
In general, mammals do not change colour during
their lifetimes but some species have particularly coloured natal coats. For example, pinniped species that
have white natal coats live in the arctic and are subject
to terrestrial predation whereas species that give birth
on islands or in caves where predation risk is low have
black natal coats (Caro et al., 2012). Artiodactyl species
that hide their young after birth have spotted neonates
(Stoner et al., 2003a). Some arctic and tundra artiodactyls and carnivores show seasonal colour change taking
on lighter coats in winter (Ortolani and Caro, 1996;
Stoner et al., 2003a). Similarly, in birds, some arctic
species have white winter plumage (Ward et al., 2007).
Other gaudy birds change colour only when they reach
sexual maturity, or revert to drab plumage out of the
breeding season (Berggren et al., 2004). All these are
strongly suggestive of colour change being linked to
predator avoidance.
Colour change is more prevalent and can be more
rapid in poikilotherms where it is used for both social
signaling and crypsis (Waring, 1963). Regarding the
latter, some morphs of Pacific tree frogs Hyla regilla
change from green to brown in a matter of weeks
(Wente and Phillips, 2003). Ambystoma barbouri salamander larvae change their colour to resemble their
background whereas A. texanum move to backgrounds
that match their colour (Garcia and Sih, 2003). Moorish
geckos Tarentola mauritanica change colour to match
their background (Vroonen et al., 2012) and dwarf chameleons Bradypodion taeniabronchum change colour in
response to both background and type of predator (Stuart-Fox et al., 2006).
Crypsis can also be behaviourally mediated with an
animal choosing a microhabitat to increase similarity to
18
Current Zoology
a background, or aligning its orientation to increase
localized similarity, or choosing a background with
greater scene complexity where searching is difficult
(Webster et al., 2011). Many vertebrates select habitats
in which they are cryptic such as spotted felids resting
and hunting in trees (Allen et al., 2011), align themselves to match background patterns such as great bitterns Botaurus stellaris pointing their bill upwards and
turning to expose their vertically striped breasts when
standing in reeds (Cott, 1940); and rest in leaf litter such
as mottled copperheads Agkistrodon contortix (Bechtel,
1978).
Usually morphological crypsis is closely associated
with behavioural crypsis as predators often detect prey
through movement (Roosevelt, 1910). For instance,
species that show morphological crypsis often move
slowly or rest quietly for considerable portions of the
day, or freeze when threatened by predators. For example, artiodactyls with spotted young lie hidden when
their mothers leave to forage (Stoner et al., 2003a); willow grouse Lagopus lagopus become motionless when
approached by a predator (Gabrielsen et al., 1985); and
lizard sit-and- wait predators show cryptic freezing behaviour when threatened whereas widely foraging species flee from predators (Vitt and Congdon, 1978).
Blotched and ringed snakes rely on immobility and
threat whereas striped and unicoloured snakes flee when
disturbed (Jackson et al., 1976). Similarly, immobility
may reduce the severity of predatory attack in salamanders (Brodie, 1977).
2.2 Countershading
Dorsal pigmentary darkening takes the form of a
light ventral surface and darker dorsum (Poulton, 1888;
Thayer, 1896; Kiltie, 1988). Many invertebrates and
vertebrates show this pattern of colouration (De Ruiter,
1956; Gomez and Thery, 2007). Dorsal pigmentary
darkening may help to make an animal cryptic through
self-shadow concealment where directional light that
would lead to the creation of shadows cast by the animal’s own body is reduced or cancelled out by countershading (Stevens and Merilaita, 2011). Alternatively, it
could reduce conspicuous brightness contrast when
viewed from above or below, especially in birds in the
air and amphibians in water; or it could reduce threedimensional cues making it difficult to be recognized as
a prey item; or it could blur the outline of an animal
when viewed from above (Rowland, 2011). Allen and
coworkers showed experimentally that countershading
in ruminants is well matched to that expected for minimizing self-shadow, and that countershading in artio-
Vol. 60
No. 1
dactyls is associated with desert habitats, small body
size and living near the equator where lighting and predation risk are intense (Stoner et al., 2003a; Allen et al.,
2012). Dorsal pigmentary darkening is so widespread in
vertebrates that it might not only be involved in countershading but could also serve in protecting the animal
from UV light, in thermoregulation or in protection
from abrasion (Rowland, 2011).
2.3 Masquerade
Another means of depriving a predator of information is through masquerade where prey recognition is
prevented by prey resembling an uninteresting object,
such as a leaf or stick (Stevens and Merilaita, 2011). It
differs from crypsis because it foils recognition rather
than detection but I have included it here for convenience. Masquerade is found in some caterpillars (Skelhorn et al., 2010a) where it has been shown to foil recognition by bird predators (Skelhorn et al., 2010b) but it
has never been formally investigated in terrestrial vertebrates and there are only a few anecdotal examples.
These include resting frogmouths Podargus strigoides
resembling the ends of broken branches (Kortner and
Geiser, 1999); tree-living colubrids with long thin bodies that look similar to vines (some Oxybelis species
move in an irregular swaying motion akin to a vine
trembling in the wind [Gower et al., 2012]); and toads
in the Rhinella typhonius group resembling a fallen leaf
(Duellman and Trueb, 1994).
2.4 Using the environment to change appearance
Some species anoint themselves with soil to change
colour. Male ptarmigan Lagopus mutus are white in
winter but they dirty their plumage at the arrival of
snowmelt in spring and as opportunities for attracting
mates dwindle (Montgomerie et al., 2001). California
ground squirrels Spermophilus beecheyi and Siberian
chipmunks Eutomias sibiricus anoint themselves with
snake scent by chewing on shed skin and then licking
themselves probably deceiving snake predators as to
their identity (Kobayashi and Watanabi, 1981; Clucas et
al., 2008). European hedgehogs Erinaceus europaeus
perform similar behaviour possibly to disguise their
smell from predators (Herter, 1965).
3 Batesian Mimicry: Dishonest Signals
3.1 Visual
In Batesian mimicry, a harmless mimic resembles an
aposematic animal, the model, so that the predator confuses the two and avoids the mimic (Mallet and Joron,
1999). Batesian mimicry is common in invertebrates
(McIver and Stonedahl, 1993; Mallet and Gilbert, 1995;
CARO T: Antipredator deception
Oxford and Gillespie, 1998). In contrast to insects
(Guilford, 1990), however, aposematism is comparatively rare in homeotherms (Dumbacher and Fleischer,
2001; Caro, 2013), and anecdotes about mammals resembling dangerous heterospecifics seem unfounded
(Caro, 2005). In venomous snakes, however, aposematism is more common and many instances of Batesian
mimicry have been reported, in particular in harmless or
mildly venomous colubrid and aniliid snakes mimicking
highly venomous elapid coral snakes in the Americas
(Greene and McDiarmind, 1981; Savage and Slowinski,
1992; Brodie, 1995). Other non-venomous snakes
mimic the highly characteristic dorsal patterns of venomous vipers (Gans, 1961; Brodie and Brodie, 2004).
Some of these mimics are imperfect (Sherratt, 2002)
either because the strong toxicity of the model makes
predators generalize across a variety of snake colour
patterns (Pough, 1988) or because of limited predator
cognitive abilities (Kikuchi and Pfennig, 2010). A behavioural example of snake mimicry is when colubrids
flatten their heads to resemble European vipers so as to
reduce attacks by raptors (Valkonen et al., 2011). Batesian mimicry has been reported in salamanders too: experimental studies show hesitancy of bird predators
attacking putative mimics of toxic model species
(Howard and Brodie, 1971; Kutchta et al., 2008).
Among poison dart frogs, non-toxic Allobates species
mimic both highly toxic or less toxic but highly conspicuous Epipedobates poison dart frog species (Darst
et al., 2006). The extent of mimetic resemblance depends on model toxicity with more precise mimicry of
less toxic models that are less immune to predatory attack (Darst and Cummings, 2006).
Less well-worked cases of mimicry include juvenile
Kalahari desert lacertids Eremias lugubris using a jerky
motion that resembles movements of noxious beetles
(Huey and Pianka, 1977). Also, pygopodids are limbless
lizards that show false strikes that might mimic the behaviour of elapid snakes (Bustard, 1968). Some frogs
produce odours that resemble those of smashed plants
perhaps misleading the predator that a larger danger is
present (Smith et al., 2004).
3.2 Acoustic
When disturbed in their burrows, burrowing owls
Athene cunicularia produce hisses that sound like an
agitated rattlesnake Crotalus viridis. California ground
squirrels with experience of rattlesnakes respond by
becoming more cautious when entering these burrows,
so it is possible that these sounds deter carnivores that
might dig for fledglings or roosting adults (Rowe et al.,
19
1986).
In Mullerian mimicry two toxic species resemble
each other so as to share predator education. Mullerian
mimics are each aposematic and advertise relatively
honestly unless levels of toxicity are very unequal.
Mullerian mimicry in vertebrates has been documented
in Pitohui birds (Dumbacher and Fleischer, 2001),
Asian pit vipers (Sanders et al., 2006) and poison dart
frogs (Symula et al., 2001).
4
Bluff: Dishonest Cues and Signals
4.1 Apparent size
Some vertebrates increase their apparent size when
threatened by predators. Piloerection in response to heterospecific and conspecific threat is well documented in
mammals. For example, many carnivores erect their
dorsal hair and appear larger when threatened (Ewer,
1968). Many avian species fluff up their feathers when
standing their ground against predators. Cobras erect
hoods and elapids and colubrids flatten their foreparts
when in a defensive posture which enlarges the size of
their heads (Greene, 1988); some crotaline viperids
thrash and raise loops of their body off the ground
(Gower et al., 2012). Corytophanes cristatus, a neotropical iguana, elevates a dorsal crest to increase its
size when viewed laterally (Davis, 1953). Some lizards
elevate frills around their throat when threatened.
Ranids, hylids and especially bufonids inflate their
bodies when in jeopardy (Marchisin and Anderson,
1978; Toledo et al., 2011). Markings and spots on
enlarged parts of the body may draw attention to an
increase in apparent size: some mammals have darker
dorsal crests, for instance. These strategies may fool
predators about true body size and are therefore dihonest signals, or make prey handling more difficult and are
therefore honest cues, or both.
4.2 Charges
Large species with weaponry may initiate bluff
charges at predators. For example, a charge by an African elephant Loxodonta africana deters most people
approaching on foot. Other large mammals including
Cape buffalo Synercus caffer and black rhinoceros
Diceros bicornis bluff charge. Large birds such as ostrich Struthio camelus will see off predators in this way.
4.3 Exaggerated threat displays
Startle signals are common in Lepidoptera where
bright patches of colour are displayed when the animal
is disturbed at rest (Stevens, 2005). In vertebrates putative examples of dishonest threat include “eyespots” on
the dorsolateral surface of the gecko Sphaerodactylus
20
Current Zoology
semasiops that may frighten predators (Thomas, 1975).
Physalaemus frogs have eyespot-like toxic glands on
their lateral skin that they display when alarmed (LenziMattos et al., 2005) but it is not clear whether this is
honest or dishonest signaling. More commonly, terrestrial vertebrates gape, hiss or spit at their persecutor
showing intention movements to bite. For example,
collared peccaries Pecari angulatus, duck-billed platypuses Ornithorhynchus anatinus, American coots Fulica
americana and crested guans Penelope purpurascens
growl, whereas young carnivores, parids and tetraonids
hiss at predators (Caro, 2005). Some testudines, such as
the common snapping turtle Chelydra serpentine, hiss
and gape; and snakes, Boidae for instance, hiss vociferously when danger threatens. Other snakes, such as
desert horned vipers Cerastes cerastes, rub body scales
together creating a hissing sound (Greene, 1988); yet
others such as the western hook-nosed snake Gyalopion
canum make popping noises by expelling air through
the cloaca (Gower et al., 2012). The Australian gecko
Nephrurus asper lunges at predators (Bustard, 1967).
Several anuran taxa open their mouths and gape at
predators (Duellmann and Trueb, 1994), others additionally scream (Toledo and Haddad, 2009). Such
threats may honestly draw attention to dangerous jaws
or teeth but may carry dishonest information about the
prey’s ability to defend itself.
Some birds utter distress calls when grasped by a
predator which serves to attract other predators but can
simultaneously startle the predator into releasing its grip
(Conover, 1994; Moller et al., 2011).
5
Feignts: Dishonest Signals and Cues
5.1 Injury
Charadiiformes, galliformes, anseriformes, columbiformes and passerines perform a wide variety of deceptive behaviours while nesting that include distraction
displays (in which the parent runs off in a crouched position resembling a small rodent); feigning injury (erratic fluttering where the bird makes convulsive attempts to run, fly, and jump); or false brooding (in
which the parent squats on the ground apparently incubating) (Gochfeld, 1984). These are instances of dishonest signaling. Many of these behaviours, such as
pretending that the wing is broken or mimicking death
throes, apparently make the parent easier to capture.
Moreover, some involve entrapment whereby the parent
returns to the intruder if it loses interest. Armstrong
(1954) outlined six factors that predispose birds to show
injury feigning: when the young are in open terrain be-
Vol. 60
No. 1
cause prey can see predators from a distance, (ii) when
the nest is accessible to non-avian predators; (iii) when
the nest is inconspicuous or insubstantial; (iv) among
birds that nest alone; (v) when predation occurs in daylight and by mammalian or reptilian predators; and (vi)
in northern latitudes with extended daylight. These
ideas constitute an interesting and novel attempt to
identify ecological drivers of deception in one group of
vertebrates.
5.2 Death
Death feigning, tonic immobility or thanatosis is
widespread in terrestrial vertebrate taxa (Dodd and Brodie, 1976; Caldwell et al., 1980; Greene, 1988; Caro,
2005) especially in birds. For example, tonic immobility
in European avian species is strongly associated with
extent of goshawk Accipter gentilis and cat Felis catus
predation (Moller et al., 2011). In reptiles, death feigning has been reported in crocodilians, snakes, testudines,
and is ubiquitous in gekkotan lizards (Greene, 1988).
Dwarf boas autohemmorrhage from the eyes and mouth;
hognosed snakes bleed from the cloaca (Gower et al.,
2012). Some anurans will flip onto their backs in a
death-like pose (Toledo et al., 2011). Rigid postures in
snakes and lizards and immobility in anurans are also
known. Superficially thanatosis in homeotherms resembles sleep but differs from it in several ways. In common possums Didelphis marsupialis, for instance, the
eyes and mouth are open in death feigning, the lateral
but not dorsal aspect is uppermost, feet and toes are
visible and flexed, the ears twitch at a sharp sound, and
no responses are elicited by prodding (Francq, 1969).
Little work has been performed on thanatosis and it may
be that, rather than providing dishonest cues that the
animal is dead, lack of movement in some prey species
confers selection benefits by depriving predators of the
necessary movement stimulus to launch a final attack
(Thompson et al., 1981).
6 Distraction: Dishonest Signals
An attack to the tail is less costly than to the head
and some species have morphological or behavioural
mechanisms for attracting attention to this part of the
body. Powell (1982) showed that trained red-tailed
hawks Buteo jamaicensis more often missed artificial
long-tailed weasels Mustela freneta that had a spot on
their tail than models with spots in other places. Iguanids and agamids sometimes elevate and wave their tails
at approaching predators before they flee which may
divert attack from the head. Snakes and amphisbaenians
may divert attack in the same way. For instance, Asian
CARO T: Antipredator deception
sand boas Eryx tataricus wave their tails which are patterned to resemble their head. Many snakes hide their
heads under coiled bodies removing this critical feature
from attack (Greene, 1988).
Lepidosaurian lizards, some salamanders, and a few
snakes and rodents autotomize their tails when attacked
(Cooper, 1998). Tails are usually shed after the tail has
been seized and may then act as a distraction especially
if they thrash as occurs in some lizards (Arnold, 1988).
Some skinks thrash their attached tail in the presence of
a snake apparently to draw the snake’s strike, the tail is
then autotomized (Cooper and Vitt, 1985). Whether
autotomy is necessarily a means of deception or a
means of providing predators with alternative food to
the prey’s body is an open question. Autotomy also occurs in some rodents but is unlikely to be deceptive as
tails are not thrashed or waved in anticipation of attack.
Some snakes, such as atractaspidine lamprophids, have
pointed hardened tail tips that they poke into predators
that have seized them which may dupe the latter into
perceiving they have been bitten.
Some snakes regurgitate recent meals when disturbed
which may distract predators from the live animal.
Defecation after being contacted by a predator is widespread in vertebrate taxa and foul smelling cloacal discharge occurs in amphibians, and in snakes, especially
large, slow ambush-hunters (Allen et al., 2013). These
may distract the attention of the predator (deception) or
provide alternative food to the body (provide resources).
Most of these antipredator defenses seem to have been
selected to signal to predators. Some appear to be honest in providing a meal or signaling noxiousness, others
appear to dishonestly attract a predator to less critical
parts of the body.
7 Flight: Dishonest Cues
Certain rodents such as kangaroo rats and artiodactyls such as Thomson’s gazelles Gazella thomsoni flee
from predators by running in zigzags; California ground
squirrels jump sideways; and great tits Parus major roll
and loop in flight. Rapid changes in flight direction or
bursts of speed could be possible forms of deception in
that they fool the predator about the path or speed of
flight. Zig-zagging, looping, twisting or sudden bouncing (termed protean behaviour, Humphries and Driver,
1967) may confuse the predator making it difficult to
select individual targets, in aiming at quarry, in pursuing
it, in concentrating attention on it, or in filtering complex information from several individuals showing different coloured surfaces or colour patches displayed in
21
or out of synchrony (Milinski, 1977; Ohguchi, 1981;
FitzGibbon, 1990); it is difficult to know whether to
interpret these as deceptive.
Motion camouflage is movement in a fashion that
decreases the probability of movement detection (Stevens and Merilaita, 2011). There are no known examples in homeotherms but it is believed to occur in some
snakes (Lindell and Forsman, 1996). Longitudinally
striped snakes and unicoloured speckled snakes can flee
quickly and it is difficult for humans to ascertain that
the animal is moving forward without individually recognizable markings such as dorsal blotches that provide
reference points. In addition, if movement is detected
the apparent velocity is lower in uniformly coloured
than blotched species (Jackson et al., 1976). A separate
point is that contrasting patterns in some snakes may
make speed and trajectory difficult to estimate (Brodie,
1992; Stevens et al., 2008).
Some species display prominent patches of colour
during flight including lagomorphs such as European
rabbits Oryctolagus cuniculus and artiodactyls such as
bushbuck Tragelaphus scriptus. Towards the end of
flight these conspicuous patches are suddenly hidden
causing prey to apparently vanish.
8
Conclusions
While antipredator deception can occur at any point
during the predatory sequence from where the predator
is searching for prey to where it is about to consume it,
our present knowledge of antipredator defenses suggests
that instances of deception other than crypsis are not
widespread in terrestrial vertebrates (see Table 1). Thus
antipredator deception in vertebrates principally relies
on depriving predators of information. Deception is
Table 1 A very crude approximation of the numbers of
species showing different types of antipredator deception
in vertebrates
Mammals
Birds
Reptiles Amphibians
Background matching
+++
+++
+++
+++
Countershading
+++
++
+++
+
+
Masquerade
+
+
Environmental use
+
+
Batesian mimicry
++
+
++
++
+++
+
+
+
++
+
++
++
Bluff
++
++
Feignts
++
Distraction
+
Flight deception
++
+++ denotes common, ++ sometimes observed, + rare; unfilled cells
denote not recorded.
22
Current Zoology
maintained in evolutionary terms if the costs to the receiver are low or if the costs of detecting cheats are very
high. Generally, most terrestrial vertebrate prey-predator
systems likely fall into the first type as predators can
always find other prey items if they are duped into failing to detect, recognize or pursue prey. Only in snake or
salamander mimicry systems are there likely to be very
high costs of trying to ascertain cheats. Snake models
can be highly venomous, potentially making mistakes in
prey classification lethal. Unlike invertebrates, absence
of toxicity in most terrestrial vertebrate taxa makes instances of Batesian mimicry unusual and this path to
deceptive trait evolution relatively rare.
How can we explain the distribution of different
forms of deception across vertebrate taxa? In every terrestrial vertebrate class evolution has favoured crypticity through background matching (Cott, 1940). This
means of avoiding detection by predators perhaps confers greatest benefits in avoiding predatory attack although it carries potential costs of restricting organisms
to certain habitats or to foraging at certain times of day
(Ruxton et al., 2004). Crypticity through self-shadow
concealment by means of dorsal pigmentary darkening
may be common in mammals although countershading
may be driven by other factors such as background
matching from above and below during flight in birds.
Reptiles and amphibians have less need to reduce self
shadow as they have short legs and move nearer to the
ground. Batesian mimicry is restricted to some groups
of snakes and salamanders. Bluff attacks and exaggerated threat displays are seen in all classes and constitute
a defense of last resort where similar-sized or smaller
predators may be intimidated. Feigning injury is principally found in birds: likely these are geared towards
duping mammalian predators but the reasons that these
are not seen in mammalian prey are unclear. Death
feigning is seen in all taxa and it deserves more study
because the extent to which this behaviour helps avoid
attack and the mechanisms by which it affects predatory
behaviour are poorly understood. Distraction behaviours
are found in only a few groups; furthermore it is not
clear whether such traits are strictly deceptive. Protean
behaviour and motion camouflage during flight is similarly difficult to attribute unequivocally to deception
(Table 1).
In summary, all classes of terrestrial vertebrates exhibit deceptive antipredator defenses but the extent to
which they are deployed by a given prey species must
depend on the background on which it lives, prey morphology and defenses, the visual capabilities and be-
Vol. 60
No. 1
haviour of the predator, its relative size compared to its
predators, and even defenses of sympatric prey species.
This eclectic mix of evolutionary drivers makes it difficult to predict where antipredator deception occurs in
nature and whether the paucity of deceptive antipredator
defenses recorded thus far in terrestrial vertebrates is
representative or simply reflects a lack of scientific attention to this topic.
Acknowledgements I thank Zhiyun Jia, Mika Mokkonen and
Carita Lindstedt-Kareksela for the invitation, Hannah Walker
for sending books, Martin Stevens for discussion, and two
anonymous reviewers for comments.
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