In
evolutionary biology
Evolutionary biology is the subfield of biology that studies the evolutionary processes (natural selection, common descent, speciation) that produced the diversity of life on Earth. It is also defined as the study of the history of life fo ...
, mimicry in vertebrates is
mimicry
In evolutionary biology, mimicry is an evolved resemblance between an organism and another object, often an organism of another species. Mimicry may evolve between different species, or between individuals of the same species. Often, mimicry f ...
by a
vertebrate
Vertebrates () comprise all animal taxa within the subphylum Vertebrata () ( chordates with backbones), including all mammals, birds, reptiles, amphibians, and fish. Vertebrates represent the overwhelming majority of the phylum Chordata, ...
of some model (an animal, not necessarily a vertebrate), deceiving some other animal, the dupe.
Mimicry
In evolutionary biology, mimicry is an evolved resemblance between an organism and another object, often an organism of another species. Mimicry may evolve between different species, or between individuals of the same species. Often, mimicry f ...
differs from
camouflage
Camouflage is the use of any combination of materials, coloration, or illumination for concealment, either by making animals or objects hard to see, or by disguising them as something else. Examples include the leopard's spotted coat, the ...
as it is meant to be seen, while animals use camouflage to remain hidden. Visual, olfactory, auditory, biochemical, and behavioral modalities of mimicry have been documented in vertebrates.
There are few well-studied examples of mimicry in vertebrates.
Still, many of the basic types of mimicry apply to vertebrates, especially among snakes. Batesian mimicry is rare among vertebrates but found in some reptiles (particularly snakes) and amphibians.
Müllerian mimicry is found in some snakes, birds, amphibians, and fish.
Aggressive mimicry is known in some vertebrate predators and parasites, while certain forms of sexual mimicry are distinctly more complex than in invertebrates.
Classification
Defensive
Batesian
Batesian mimicry
Batesian mimicry is a form of mimicry where a harmless species has evolved to imitate the warning signals of a harmful species directed at a predator of them both. It is named after the English naturalist Henry Walter Bates, after his work on bu ...
is a form of defense that allows a harmless species to mimic the appearance of a toxic, noxious, or harmful species to protect itself from predators. By mimicking the appearance of a harmful species, a predator is less likely to attack the species due to its awareness of the signal of warning color patterns. Batesian mimicry occurs in multiple vertebrates, but is less prevalent in mammals due to a relative rarity of well-marked harmful models. However, this form of mimicry is prevalent in snakes and frogs, where chemical defense has coevolved with distinct coloration. Still, mammals have evolved Batesian mimicry systems where particularly powerful or harmful models exist.
![Venomous and nonvenomous coral snake coloration illustration](https://upload.wikimedia.org/wikipedia/commons/7/7e/Venomous_and_nonvenomous_coral_snake_coloration_illustration.jpg)
For example, Batesian mimicry may occur in
cheetah
The cheetah (''Acinonyx jubatus'') is a large cat native to Africa and central Iran. It is the fastest land animal, estimated to be capable of running at with the fastest reliably recorded speeds being , and as such has evolved specialized ...
cubs. They replicate the appearance of a
sympatric
In biology, two related species or populations are considered sympatric when they exist in the same geographic area and thus frequently encounter one another. An initially interbreeding population that splits into two or more distinct species sh ...
species, the
honey badger
The honey badger (''Mellivora capensis''), also known as the ratel ( or ), is a mammal widely distributed in Africa, Southwest Asia, and the Indian subcontinent. Because of its wide range and occurrence in a variety of habitats, it is listed ...
(''Mellivora capensis).'' The honey badger has a white or silvery back with a black or brownish underbelly and grows to a body length of about three feet long and ten inches high. As cubs, cheetahs have the same reverse-
countershading
Countershading, or Thayer's law, is a method of camouflage in which an animal's coloration is darker on the top or upper side and lighter on the underside of the body. This pattern is found in many species of mammals, reptiles, birds, fish, and ...
color pattern and are roughly the same size. Due to this conspicuous coloration, potential predators like lions and birds of prey are less likely to hunt cheetah cubs, as from a distance they appear to be honey badgers. Honey badgers make an effective model because their aggressive nature and glands on their tails that produce a noxious fluid enable them to deter predators up to 10x its size.
Batesian mimicry also occurs in the
scarlet kingsnake
The scarlet kingsnake or scarlet milk snake (''Lampropeltis elapsoides'') is a species of kingsnake found in the southeastern and eastern portions of the United States. Like all kingsnakes, they are nonvenomous. They are found in pine flatwoods, ...
. This species resembles the venomous
coral snake
Coral snakes are a large group of elapid snakes that can be divided into two distinct groups, the Old World coral snakes and New World coral snakes. There are 16 species of Old World coral snakes, in three genera (''Calliophis'', '' Hemibungarus' ...
, sharing a pattern of red, black, and yellow bands. Although the order of the color rings differ between the two snakes, from a distance a predator can easily mistake the scarlet kingsnake for its venomous model.
Müllerian
Müllerian mimicry
Müllerian mimicry is a natural phenomenon in which two or more well-defended species, often foul-tasting and sharing common predators, have come to mimic each other's honest warning signals, to their mutual benefit. The benefit to Müllerian ...
is another form of defensive mimicry, except the system involves two or more species that are all toxic, noxious, or harmful. These species develop similar appearances to collectively protect against predators. This adaptation is said to have evolved due to the additive protection of many species that look the same and reliably have harmful defenses. That is to say, this mimicry system evolves convergently. If a predator is aware of the potential threat of one species, the predator will also avoid any species with a similar appearance, creating the Müllerian mimicry affect. Again, the relative lack of noxious models limits most examples to systems that involve reptiles or amphibians.
Müllerian mimicry is found in many
pitvipers
The Crotalinae, commonly known as pit vipers,Mehrtens JM (1987). ''Living Snakes of the World in Color''. New York: Sterling Publishers. 480 pp. . crotaline snakes (from grc, κρόταλον ''krotalon'' castanet), or pit adders, are a subfa ...
. All pit vipers are capable of delivering a life-threateningly venomous bite. In Asia, different species found throughout Asia have evolved separately to have a very similar appearance. Each species is found in different places in Asia, but have the same green coloration with reddish tail tip. These shared colorations are warnings signals for predators. Because a predator is aware of these warning signals, it will avoid all species with this color pattern. Species that benefit from this system include ''
Trimeresurus macrops'', ''
T. purpureomaculatus'', ''
Trimeresurus septentrionalis
''Trimeresurus septentrionalis'', commonly known as the Nepal pit viper or northern white-lipped pit viper,Gumprecht A, Tillack F, Orlov NL, Captain A, Ryabov S. 2004. ''Asian Pitvipers''. GeitjeBooks. Berlin. 1st Edition. 368 pp. . is a venom ...
'', ''
T. flavomaculatus'' and ''
T. hageni''.
Müllerian mimicry is also found in a ring of poisonous frog species in Peru. The mimic poison frog ''
(Dendrobates imitator)'' mimics 3 similarly poisonous frogs of the same genus that live in different areas. These are ''
D. variabilis'', ''
D. fantasticus,'' and ''
D. ventrimaculatus''.
''D. imitator'' can replicate the different appearances of all 3 species with color patterns ranging from black spots with yellow back and bluish green limbs, larger black spots with yellow outline, and black linear spots with yellow and bluish green outline.
![Slow lorises in defensive posture - 1678-9199-19-21-2](https://upload.wikimedia.org/wikipedia/commons/4/46/Slow_lorises_in_defensive_posture_-_1678-9199-19-21-2.png)
The
slow loris
Slow lorises are a group of several species of nocturnal strepsirrhine primates that make up the genus ''Nycticebus''. Found in Southeast Asia and bordering areas, they range from Bangladesh and Northeast India in the west to the Sulu Archipe ...
is one of the few known
venomous mammals
Venomous mammals are animals of the class Mammalia that produce venom, which they use to kill or disable prey, to defend themselves from predators or conspecifics or in agonistic encounters. Mammalian venoms form a heterogeneous group with differe ...
, and appears to use Müllerian mimicry for protection. It is hypothesized that this venom may have allowed it to develop a system of Müllerian mimicry with the
Indian cobra
The Indian cobra (''Naja naja''), also known as the spectacled cobra, Asian cobra, or binocellate cobra, is a species of cobra found in India, Pakistan, Bangladesh, Sri Lanka, Nepal, and Bhutan, and a member of the "big four" species that are ...
. Slow lorises appear to look similar to the cobras with "facial markings undeniably akin to the eyespots and accompanying stripes of the spectacled cobra". Dark contrasting dorsal stripes are also apparent in both species,, helping to confuse predators from above. When in aggressive encounters, slow lorises will make a grunting noise that mimics the hiss of a cobra. This example of Müllerian mimicry is likely unique to vertebrates due to its multiple modalities: biochemical, behavioral, visual, and auditory. Since the cobra is undoubtedly more dangerous to predators (and prey, as the loris eats predominantly fruits, gums, and insects), it is unclear if the benefit from this system is mutual; Still, both species are dangerous in their own right, and can therefore most accurately be classified as Müllerian.
Aggressive
Aggressive mimicry
Aggressive mimicry is a form of mimicry in which predators, parasites, or parasitoids share similar signals, using a harmless model, allowing them to avoid being correctly identified by their prey or host. Zoologists have repeatedly compared t ...
is a form of mimicry, opposite in principle to defensive mimicry, that occurs in certain
predators
Predation is a biological interaction where one organism, the predator, kills and eats another organism, its prey. It is one of a family of common feeding behaviours that includes parasitism and micropredation (which usually do not kill the ...
,
parasite
Parasitism is a close relationship between species, where one organism, the parasite, lives on or inside another organism, the host, causing it some harm, and is adapted structurally to this way of life. The entomologist E. O. Wilson has ...
s or
parasitoid
In evolutionary ecology, a parasitoid is an organism that lives in close association with its host (biology), host at the host's expense, eventually resulting in the death of the host. Parasitoidism is one of six major evolutionarily stable str ...
s. These organisms benefit by sharing some of the characteristics of a harmless species in order to deceive their prey or
host
A host is a person responsible for guests at an event or for providing hospitality during it.
Host may also refer to:
Places
* Host, Pennsylvania, a village in Berks County
People
*Jim Host (born 1937), American businessman
* Michel Host ...
. Most examples of aggressive mimicry involve the predator employing a signal to lure its prey towards it under the promise of food, sex, or other rewards—much like the idiom of a
wolf in sheep's clothing
A wolf in sheep's clothing is an idiom of Biblical origin used to describe those playing a role contrary to their real character with whom contact is dangerous, particularly false teachers. Much later, the idiom has been applied by zoologists to v ...
.
In predators
Some predators pretend to be prey or a third-party organism that the prey beneficially interacts with. In either situation, the mimicry increases the predator's chances of catching its prey.
One form of predatory mimicry,
lingual luring, involves wriggling the tongue to attract prey, duping them into believing the tongue is a small worm, an unusual case of a vertebrate mimicking an invertebrate. In the puff adder ''
Bitis arietans
The puff adder (''Bitis arietans'') is a viper species found in savannahs and grasslands from Morocco and western Arabia throughout Africa except for the Sahara and rainforest regions.U.S. Navy. 1991. ''Venomous Snakes of the World''. US Govt. ...
'', lingual luring only occurs in the act of attracting amphibian prey, suggesting that puff adders distinguished between prey types when selecting how to perform a display of aggressive mimicry.
Another form of aggressive mimicry is
caudal luring
Caudal luring is a form of aggressive mimicry characterized by the waving or wriggling of the predator's tail to attract prey. This movement attracts small animals who mistake the tail for a small worm or other small animal. When the animal approac ...
, in which the tail is waved to mimic prey. By mimicking invertebrate larva, the predator attracts prey of small vertebrates such as frogs, lizards, and birds. Male puff adders have longer, more obvious-looking tails.
Sidewinder rattlesnakes, puff adders, lanceheads, and multiple other ambush-predatory snakes use caudal luring to attract prey.
Complicated forms of aggressive mimicry have also been observed in fish, creating a system that resembles Batesian mimicry. The
false cleanerfish
The false cleanerfish (''Aspidontus taeniatus'') is a species of combtooth blenny, a mimic that copies both the dance and appearance of ''Labroides dimidiatus'' (the bluestreak cleaner wrasse), a similarly colored species of cleaner wrasse. It ...
, ''Aspidontus taeniatus'', is a fin-eating blenny that has evolved to resemble a local species of cleaner wrasse, ''
Labroides dimidiatus
The bluestreak cleaner wrasse, ''Labroides dimidiatus'', is one of several species of cleaner wrasses found on coral reefs from Eastern Africa and the Red Sea to French Polynesia. Like other cleaner wrasses, it eats parasites and dead tissue o ...
'', which engages in
mutualistic cleaning with larger fish. By closely mimicking the coloration and the cleaner fish's distinctive dancing display, false cleanerfish are able to remain in close quarters with large predatory reef fish, and gain access to victims during foraging.
Some aggressive mimics switch rapidly between aggressive mimicry and defensive behavior depending on whether they are in the presence of a prey or a potential predator. For example, the sidewinder rattlesnake ceases aggressive behavior upon the arrival of a predatory toad and begins species-typical defensive displays.
Host-parasite
Host-parasite mimicry is a form of aggressive mimicry in which a parasite mimics its own host.
Brood parasitism
Brood parasites are animals that rely on others to raise their young. The strategy appears among birds, insects and fish. The brood parasite manipulates a host, either of the same or of another species, to raise its young as if it were its own ...
is a common form of parasitic aggressive mimicry that occurs in vertebrates, with cuckoos being a notable example. Brood parasite mothers will surrender their offspring to be raised by another organism, of either the same or a different species, unbeknownst to the other organism. This allows the progeny to be nurtured without energy expenditure or parental care by the true parent.
![Cuckoo Eggs Mimicking Reed Warbler Eggs](https://upload.wikimedia.org/wikipedia/commons/e/ef/Cuckoo_Eggs_Mimicking_Reed_Warbler_Eggs.JPG)
Cuckoos are brood parasites that lay their eggs to match the color and pattern of their host's own eggs. Different species of cuckoo hatchlings have been known to mimic the acoustic sound, such as during begging, and appearance of the host offspring.
Unlike most vertebrates that perform aggressive mimicry, certain brood parasitic birds display signals of two distinct modalities at the same time. For example,
Horsfield's bronze cuckoo
Horsfield's bronze cuckoo (''Chrysococcyx basalis'') is a small cuckoo in the family Cuculidae. Its size averages 22g and is distinguished by its green and bronze iridescent colouring on its back and incomplete brown barring from neck to tail. Hor ...
nestlings have been found to employ both acoustic and visual sensory modalities at the same time to increase efficiency and success of their mimicry.
However, host-parasite systems are not always as precise.
Great spotted cuckoo
The great spotted cuckoo (''Clamator glandarius'') is a member of the cuckoo order of birds, the Cuculiformes, which also includes the roadrunners, the anis and the coucals.
It is widely spread throughout Africa and the Mediterranean Basin. It i ...
s are brood parasites that lay eggs that can successfully dupe other birds such as the
magpie
Magpies are birds of the Corvidae family. Like other members of their family, they are widely considered to be intelligent creatures. The Eurasian magpie, for instance, is thought to rank among the world's most intelligent creatures, and is one ...
,
pied starling
The pied starling or African pied starling (''Lamprotornis bicolor'') is a bird endemic to South Africa, Lesotho and Eswatini. It is common in most of its range, but largely absent from the arid northwest and the eastern lowlands of South Afric ...
, and
black crow, despite having different egg color, egg size, and offspring features. It is hypothesized that these differences in characteristic have evolved after the mimicry system due to
genetic isolation, as the appearance of eggs laid by European an African great spotted cuckoos are different.
Evidence also exists for other forms of parasitic mimicry in vertebrates. One such form is interspecific social dominance mimicry, a type of social parasitism where a subordinate species (usually determined by size) evolves over time to mimic its dominant ecological competitor, thereby competing with its previously socially dominant opponent.
One such example is found in the
tyrant flycatcher
The tyrant flycatchers (Tyrannidae) are a family of passerine birds which occur throughout North and South America. They are considered the largest family of birds known to exist in the world, with more than 400 species. They are the most dive ...
family, in which different birds of similar appearance exist from six different genera. Smaller-bodied species from four genera have been found to mimic the appearance of the larger species of the other two genera, suggesting that an avian mimicry complex has contributed to
convergent evolution
Convergent evolution is the independent evolution of similar features in species of different periods or epochs in time. Convergent evolution creates analogous structures that have similar form or function but were not present in the last com ...
, providing a competitive advantage in the same ecological niche.
Automimicry
Automimicry
In zoology, automimicry, Browerian mimicry, or intraspecific mimicry, is a form of mimicry in which the same species of animal is imitated. There are two different forms.
In one form, first described by Lincoln Brower in 1967, weakly-defended m ...
is a type of mimicry that occurs within a single species, in which an individual mimics either a different member of its own species or a different part of its own body. In some cases, it is considered a form of Batesian mimicry, and is exhibited by a wide variety of vertebrates. Many of the basic strategies automimics use in invertebrates is repeated in vertebrates, such as eyespots.
Sexual
In
sexual mimicry Sexual mimicry occurs when one sex mimics the opposite sex in its behavior, appearance, or chemical signalling. It is more commonly seen within invertebrate species, although sexual mimicry is also seen among vertebrates such as spotted hyenas. Sexu ...
, an organism mimics the behaviors or physical traits of the opposite sex within its species.
Spotted hyena
The spotted hyena (''Crocuta crocuta''), also known as the laughing hyena, is a hyena species, currently classed as the sole extant member of the genus ''Crocuta'', native to sub-Saharan Africa. It is listed as being of least concern by the IUC ...
s are one of the few vertebrate examples. In spotted hyenas, females have a pseudo-penis, which is highly erectile clitoral tissue, as well as a false scrotum. Females have evolved to mimic or exceed the testosterone levels of males
This is advantageous because it lends females heightened aggression and dominance over the males in a highly competitive environment. Alternatively, it may have evolved for the advantage it bestows upon sexually indistinguishable cubs, which experience a high level of female-targeted infanticide.
Another example is in
flat lizards, where some males imitate female coloring to
sneak around more dominant males and achieve copulation with females.
Anatomical
![Glaucidium californicum Verdi Sierra Pines 2 (cropped)](https://upload.wikimedia.org/wikipedia/commons/f/ff/Glaucidium_californicum_Verdi_Sierra_Pines_2_%28cropped%29.jpg)
Some vertebrates species self-mimic their own body parts, through the use of patterns or actual anatomy. Two widespread examples of this are eyespots and false heads, both of which can misdirect, confuse, or intimidate potential predators.
Eyespots are a form of
automimicry
In zoology, automimicry, Browerian mimicry, or intraspecific mimicry, is a form of mimicry in which the same species of animal is imitated. There are two different forms.
In one form, first described by Lincoln Brower in 1967, weakly-defended m ...
in which an organism displays false eyes on a different part of its body, considered to be an aversion to predators who believe the prey animal has spotted them or is behaving aggressively, even when they are actually facing the other direction and unaware. In the case of attack, eyespots may also redirect damage away from the true head. Eyespots can be seen across the vertebrate taxa, from the
four-eyed butterfly fish to
pygmy owls.
False-head mimicry occurs when an organism displays a different body part that has evolved to look like a head, achieving the same scare tactic as eyespots, and also protecting the vulnerable and important real head. For example, the rubber boa coil up and hide their heads, instead displaying their tails, which look morphologically like their heads, in a defensive behavior.
Evolution
Mimicry, in vertebrates or otherwise, is widely hypothesized to follow patterns of
directional selection
In population genetics, directional selection, is a mode of negative natural selection in which an extreme phenotype is favored over other phenotypes, causing the allele frequency to shift over time in the direction of that phenotype. Under dir ...
. However, it is argued that, while positive evolution might stabilize mimic forms, other evolutionary factors like random mutation create mimetic forms simply by coincidence. Vertebrate evolution systems often operate under unique selective pressures, resulting in the different quantitative and qualitative characteristics we observe between mimicry in vertebrates and other animals.
The primary difference between mimicry in vertebrates and in insects is a decreased diversity and frequency. The 50,000 extant vertebrates are dwarfed by the over 1 million known invertebrates. This might create a
negative feedback loop
Negative feedback (or balancing feedback) occurs when some function of the output of a system, process, or mechanism is fed back in a manner that tends to reduce the fluctuations in the output, whether caused by changes in the input or by other ...
for vertebrates whereby fewer examples of mimicry arise due to a rarity of species to mimic, and may help to explain the relative scarcity of precise mimicry in vertebrates. Vertebrates seem to have multiple barriers to precise mimicry that invertebrates do not. Due to the drastic difference in average body size between the two phyla, vertebrates tend to mimic other living things, while invertebrates are much better able to mimic inanimate objects.
Large size makes any imprecision much more noticeable to the naked eye, slowing or preventing the evolution of mimicry. However, when a potential prey is highly noxious, as in snakes, predators that avoid even poor mimics gain a strong selective advantage; whereas insects, rarely able to deliver enough toxin to threaten vertebrate predators, would need precise mimicry to avoid detection.
The assumption of scarcity in vertebrate mimetic resemblances is largely limited due to human perception. Humans are hyper-perceptive to visual mimicry systems, and find these the most abundant. However, olfactory, biochemical, and even electroreceptive forms of mimicry are likely to be much more common than currently accounted for.
References
{{mimicry
Mimicry
Evolution of vertebrates