Mimicry - When Animals Copy Other Animals

this is henry walter bates a british naturalist and explorer that lived in the 19th century he became famous for his expedition into the amazon rainforest in the 1840s and 50s during which he collected over 14 000 species of insects and other animals most of them knew to science but as opposed to many of his colleagues at the time he not only collected these rare and unknown species but also studied their behaviors and into relationships to gain a better understanding of their role in the ecosystem it was during these studies that a conspicuous looking butterfly caught his attention a butterfly of the tribe ethomine he noticed that although these butterflies were incredibly abundant and slow flying never once had he observed them getting eaten by one of the many insect predators in these forests he concluded that they must be unpalatable that they tasted so bad that no predator would consider hunting them but there was more to them after catching and collecting a number of individuals bates realized that among these colorful and conspicuous looking butterflies were a small number of butterflies of an entirely different family the dysmorphia he was fascinated by how remarkably close they resembled the ithomini in terms of wing shape coloration and flight behavior much more so than they resembled their closer relatives which were also common in the area in flight they were basically indistinguishable on its own this could have been a coincidence but bates quickly discovered more and more examples of this it seemed all over the amazon rainforest dysmorphia and ithomini species perfectly resembled each other [Music] when bates returned back to britain in 1859 after spending nearly 11 years in the amazon another now famous naturalist was about to publish what would become one of the most important books in biology darwin's on the origin of species introduced the idea that life is not as previously believed static but instead continuously changing evolving over the course of thousands of generations through a process of natural selection darwin noted that within each population of animals there were variations variations in speed in size in strength in shape and so on because of the limited resources and the competition between individuals and populations those best adapted are more likely to survive and reproduce and as a result favorable variations would tend to be preserved and enhanced while unfavorable ones would be destroyed this process of natural selection would inevitably lead similar to artificial selection involved in selective breeding to a continuous transformation and diversification of life but while natural selection seemed to explain almost everything in nature it couldn't readily explain what bates had observed why would there be an evolutionary incentive for multiple distantly related groups of animals that share the same habitat to adopt the same forms and colors what would be the selective pressure one important thing that bates had noticed pretty quickly was that many other species from the family the dysmorphia belonged to species that didn't share a resemblance to the ethomony frequently fell victim to birds and this was despite the fact that they were much more capable flyers than most butterflies so it seemed that this family of butterflies was not generally unpalatable for predators which was therefore likely also the case for the dysmorphia species that did share a resemblance with the ethomony this led bates to the conclusion that this form of evolution must be driven by predatory selection that a palatable species would gain protection from predators by resembling an unpalatable or otherwise unprofitable species because the dysmorphia had evolved the similar shape and warning coloration as ithomini species in the area and also adopted their general behavior such as slow flying speed any predator that had enough bad experiences with the unpalatable ithalmini to learn to avoid them would also avoid the dysmorphia in the future as long as the models are more common than the mimics this would give the mimics an effective protection and an increased survival rate despite the fact that they're not defensive themselves this phenomenon later named batesian mimicry because of his discovery was quickly realized to be another prime example of the power of natural selection and was subsequently included by darwin in later editions of on the origin of species [Music] two things are important to understand about batesian mimicry and mimicry in general first is that it is an evolutionary process no mimic consciously tries to imitate another animal this would not be considered mimicry in a biological sense this is easy enough to understand when we are looking at appearance but cases of mimicry can also involve sounds smells or behaviors take for instance the cenerius mourner this bird endemic to the forests of south america utilizes mimicry to protect its offspring with its bright orange feathering the chicks have a strong resemblance to the caterpillars of the flannel moth although their fluffy hairs give the caterpillars quite a cute appearance touching them would actually be extremely painful that's because what looks like hairs are actually venomous spines that upon contact cause paralysis inflammation and extreme pain described by victims as similar to the pain you'd feel from a broken bone any predator that has ever had the misfortune of having this experience will likely be very wary of anything that looks even remotely like the caterpillar including the helpless chick of the cenerius mourner to make this deception even more convincing however the chick is also mimicking the caterpillar's behavior whenever its mother is out and about looking for food it crouches down and only moves very slowly swinging its head rhythmically from side to side this is again not something the chick does consciously it isn't aware that it's mimicking the caterpillar nor is it aware of the caterpillar's existence it is an innate instinctive behavior that the cenarius mourner has developed and refined over thousands of generations because it increased their chick survival rate likewise the burrowing owl uses mimicry as a defense strategy by mimicking sounds being primarily ground bound these tiny owls that nest in the burrows of other animals most commonly ground squirrels are in constant danger from predators such as foxes coyotes badgers and cats their only real protection against these predators when inside their burrows is their distinct warning call that mimics the warning of rattlesnakes because many animals have an innate fear of snakes this is an effective strategy to protect their nests the other important thing to understand about mimicry is its distinction to camouflage although the terms are sometimes used interchangeably there is an important difference between them while camouflage evolves as a way to hide from potential predators or prey by blending in with the environment mimicry specifically evolves to be detected the effectiveness of mimicry heavily relies on sending the target a distinct signal that it can easily identify even though it is of course a dishonest signal in this case take for instance the caterpillars of the peppered moth these caterpillars are a very impressive example of camouflage blending in with the twigs they sit on almost perfectly they even possess the ability to sense the color of the twig and change their body color accordingly these caterpillars however have an additional trick up their sleeves when they sense danger they can inflate their front end to form what looks surprisingly well like a snake's head eye spots and rhythmic body movements sell the illusion even better there are actually quite a few caterpillars that use this form of deception some of them even have a special appendage that they can push out of their heads to mimic a slithering snake another example that makes the difference between camouflage and mimicry very clear is the cheetah these large cats are very well camouflaged to stalk and hunt in the african grasslands but also to remain hidden from potential dangers such as hyenas or lions particularly their cubs are vulnerable to other predators curiously however they sport a distinctively different look as the adults their fur is much darker especially during the first few weeks of their lives with a conspicuous looking stripe of long light fur across their back this is thought to make them look like honey badgers a small aggressive carnivore that lives in parts of africa the middle east and india and that is known for its extremely aggressive and fearless nature they are frequently observed fighting off much larger animals like lions leopards and hyenas pair this with their ability to produce a strong smelling fluid with special anal glands that they can use to deter predators and it's easy to see why they make such a good model and although this is not a very convincing example of mimicry not yet anyway it might still give cheetah cubs a slightly better chance of survival all examples we have discussed this far are of course examples of batesian mimicry where a harmless animal mimics the warning signals of an unpalatable poisonous or otherwise defensive animal to fool predators that have learned to avoid this particular warning signal one example of batesian mimicry that most people will recognize and maybe even fell for themselves is found in hoverflies these little insects that can be found on all consonants except antarctica sport a very distinctive yellow and black coloration that mimics the bright warning signals of bees and wasps in particular and yet they are completely harmless but because the distinctive coloration is so easily recognizable it provides them with an effective protection against many predators including wasps themselves which tend to not attack their peers mimicking wasps seem to be such an effective strategy that a whole range of animals use it you can find it in beetles like the locust borer or the wasp beetle in a few mantid flies and even in this little jumping spider but probably the most impressive examples are found in moths [Music] another insect that frequently falls victim to this kind of mimicry are ants because ants are very aggressive and many have poisonous bites or stings they are usually seen as an undesirable prey item but equally as important are their numbers while not the most diverse family of insects that title belongs to the snout beetles they are certainly the most numerous insects with estimates ranging from somewhere between 10 to 100 quadrillion individuals even the lower estimate would mean that for each human there are roughly 1.5 million ants in the world enough ants for continuous ant trails on the orbits of mercury venus earth mars jupiter saturn and uranus why is this so important how numerous the model is is obviously one of the most important factors in determining the effectiveness of mimicry for a group of harmless mimics to effectively hide inside a group of defensive models the number of models should ideally be much larger than the number of mimics which makes ants of course a prime target for defensive mimicry in fact ant mimicry is probably the most common form of mimicry there are literally thousands of examples it is especially common among spiders particularly jumping spiders more than 300 species use it as a defense strategy some of them even permanently raised their four legs in the air like a pair of antennae this spider seemingly mimics a weaver ant worker carrying another worker the distinct pheromone that ants use to communicate can also be mimicked not just the appearance this allows them to live among them undetected but there are many other animals too that mimic ants among insects you can find examples in basically every major group such as beetles bugs [Music] flies certain species of wingless wasps these cicadas and even this moth often times however you can see it in the larval and nymphal stages of insects that prior to their metamorphosis into the adult form are much smaller and more vulnerable like in these nymphal stages of praying mantises or in these grasshopper nymphs [Music] this caterpillar also seems to mimic ants as well as these stick insects [Music] another popular model for basey and mimicry are ladybugs when they feel threatened they are able to release a foul tasting fluid from the joints in their legs which makes them a very unappetizing meal mimics include other beetles that don't possess this defensive ability as well as spiders and this cockroach but mimicry isn't exclusively found in land animals it has also evolved in various species of fish this is the sharpnose puffer a species of puffer fish that lives in tropical coral reefs across the world like many of their close relatives they carry a potent neurotoxin in their skin and their inner organs which makes these fish extremely poisonous sharpness puffers typically organize themselves into harems of 5 to 10 individuals consisting of a dominant male 1 or more females and their offspring among these harems you will however often find another fish these non-poisonous mimics resemble the puffer fish to almost complete perfection they even mimic their swimming behavior the only real way to tell them apart is their dorsal fin which is much larger in the false puffer fish the harmless banded snake eel mimics another famously deadly ocean animal sea snakes this allows them to swim freely during the day as opposed to other snake eels which tend to only come out under the cover of darkness these cases of mimicry also teach us a lot about the predators in the ocean especially about their eyesight it was long thought that most fish have very poor eyesight however the fact that copying sea snakes and especially the puffer fish and its intricate patterns in coloration to such perfection gives the mimics an evolutionary advantage only makes sense if the predators that live in the reef have indeed exceptional eyesight likely comparable to our own however batesian mimicry is as alluded to earlier not the only form of defensive mimicry and then there is also aggressive mimicry which includes some of the most malicious examples of mimicry but more on that later during his studies in the amazon bates also found many examples of an apparently different form of mimicry several species of butterflies which were all known to be unpalatable or toxic to predators also appeared to resemble one another this was especially obvious in the case of heliconius erato and heliconius melhamony these butterflies that exist all over the amazon rainforest show significant color variations within each species their distinct warning signals on their wings differ substantially from region to region you can see it here in heliconia serato the color patterns change every few hundred kilometers curiously however when you compare these with the color patterns of heliconius mel palminate similarly sorted after region you can see that they resemble each other almost perfectly in each of the regions bates could not explain this there seemed to be no logical reason for any of these two butterflies to mimic the other given that both share the same protection 20 years later fritz muller a german zoologist proposed a possible explanation for this paradox the reason many defensive animals use distinctive warning coloration is because more often than not predators do not inherit the ability to recognize inedible or defensive prey but instead have to learn to avoid it the more distinct this warning signal is and the more easily a predator can thereby recognize and remember to avoid it the faster this learning process is but it still of course often comes to the detriment of the individual teaching the lesson an economic cost that has to be paid for the warning signal to work mueller suggested that the explanation for this form of mimicry might lie in the advantage to one defensive species and having a predator learn from another he argued that by using the same warning signal different species could effectively split the economic cost as once a predator has learned to avoid this particular pattern all animals that use it would be avoided in the future this would give multiple defensive species that share a geographic range and evolutionary incentive to evolve similar warning signals and to generally converge in appearance over time so as opposed to batian mimicry where the mimic gains a benefit to the disadvantage of the model and malaria mimicry the benefits are mutual today this evolutionary mechanism is very well documented particularly in insects and other arthropods take these poisonous millipedes of the genera afaloria and brachoria for example these arthropods produce enough hydrogen cyanide to kill a full-grown eagle and their bold color patterns make this very clear to any potential predator in the areas where the ranges of these millipedes overlap you can again see a similarity of their warning signals these beetles and these moths from north america both toxic also share a same orange and black color pattern in fact a whole handful of insect species from the americas do which highlights another important point although malaria mimicry is often for simplicity described with only two species of animals in nature malaria mimics often form intricate mimicry complexes so-called mimicry rings you can see it very well in these 50 species of velvet ants from north and central america which can be sorted into five to six regionally distinct mimicry rings in which all species share a visible resemblance of their warning coloration the mimicry rings are further expanded by several species of spider wasps that in their respective geographic ranges also share those warding patterns likewise the roughly 250 species of bumblebees which can further be divided into roughly 400 different color variants also show convergence onto about 25 regionally and morphologically distinct memetic color patterns across their range these patterns are often also shared by batesian mimics in each region showcasing the complexity of mimicry systems particularly in insects but you can find examples in other groups such as reptiles amphibians fish and even in birds and mammals the mimic poison frog for instance resembles three different model species simultaneously in different geographic regions several pitohui species from new guinea also seem to form a malaria mimicry ring these birds are among the only known toxic bird lineages on earth their toxicity stems from a potent neurotoxin they carry in their feathers and in their skin it actually belongs to the same family of toxins found in many poison arrow frogs like the frogs the birds also don't seem to create the toxin themselves but instead sequester it from their diet this might explain why the toxicity levels in the various populations vary quite significantly in areas where toxicity levels are high presumably because their toxic prey makes up a higher percentage of their overall diet you can again see that the various species have seemingly evolved the same contrasting black and orange plumage which is believed to protect them from bird predators such as snakes speaking of snakes one mimicry system that is very well known is found in coral snakes and their mimics this system contains roughly 20 percent of all snake species in the americas some 200 in total they include anything from highly venomous over mildly venomous to completely harmless snakes while the exact evolutionary relationships between the various mimics and the models in this system are still debated the easily recognizable warning coloration they all share could be shown to be very effective in deterring predators with some even instinctively avoiding it like the turquoise brown montmart which seems to have evolved an innate ability to avoid these snakes and therefore doesn't need to learn it this is actually very important because of an often discussed paradox regarding coral snakes since their venom is so strong it should kill almost any predator they encounter making a learning effect obviously impossible why do they use warning coloration instead of camouflage and why would another species profit from mimicking them after all predator learning is one of the key mechanisms for both batesian and malaria mimicry to work this apparent contradiction had previously led some to propose that it's actually the deadly coral snakes that are the mimics that by mimicking the warning of mildly venomous snakes they would gain protection from their common predators while this does provide a logical explanation there are many other possible solutions to explain warning coloration in coral snakes including a native voids highly venomous prey often exerts a strong selective pressure on predators to evolve such an innate avoidance because many encounters end deadly for the predators given that red and black warning coloration could be shown to have evolved independently in coral snakes before it did in many of its supposed models which shows that it must be effective on its own even when paired with a highly potent venom and given that there also exist many examples of non-venomous snakes that use patterns that clearly resemble those of their local coral snake species martensian mimicry as it is sometimes called remains controversial even in its case example of coral snakes [Music] whether or not it is true in some unique cases this further subdivision of mimicry seems to be unnecessary and creates more problems than it solves even malaria mimicry is even though it is well documented as we have seen not without controversy one obvious problem can be seen in most of the aforementioned examples if the evolutionary processes that generate malaria mimicry promote uniformity then why are malaria mimics notorious for their geographic variation take heliconius errado and heliconius melpany for instance while both species mimic each other to almost complete perfection in any given region they remarkably vary or co-vary from region to region exhibiting more than a dozen different color patterns at different locations throughout their range this so-called spatial polymorphism seems at odds with the selection for uniformity and against rarity attributed to malaria and mimicry although the diversity among malaria mimics seems odd at first why this diversity is maintained is actually not that difficult to explain in fact it can very easily be explained by the same processes that are responsible for the evolution of mimicry namely selection against rarity or positive frequency dependent selection how it is formally called we already talked about this but to reiterate if we say like mueller assumed each predator has to consume a fixed number of samples of each form until it learns to avoid it rare forms are preyed upon proportionally more often and thus faces selective pressure to become more like common forms strength in numbers essentially a simple explanation for why these mosaics persist could therefore be that once strong and distinct mimicry rings have formed in each region intermediates between the two would be because of their rarity at such an evolutionary disadvantage that further convergence of the various morphs is improbable this can be shown by simple mathematical models when you start with two populations dispersed over a large area one rare and one common in which each individual can occur in any of 10 different forms randomly then over the generations a spatial mosaic will form naturally not only do the rarer forms in each region become more like the common forms the rare species similarly evolve to resemble the common species however this only works when you already start with those 10 different forms it doesn't create new ones so it only provides an explanation for why the diversity is maintained and not where it initially came from this is actually a lot more difficult to make sense of a simple explanation could be through separation populations that are isolated from one another through natural barriers such as mountain ranges or rivers or simply by very large distances will likely evolve to a certain degree independently from one another for instance because of subtle differences in the environment they inhabit or simply through random chance this could very easily also affect their warning coloration and therefore explain why different patterns became dominant so to speak in different regions after all many of today's malaria mimics evolved roughly at the end of the last ice age which was a time of great environmental change another way to attack this problem is to look at predatory behavior the evolution of mimicry of course rests to an overwhelming degree on the way how predators sample unfamiliar prey muller's model in which each predator has to sample a fixed number of individuals before a learning effect is achieved would always result in the selection against rarity however this model is very rigid and in reality animal behavior is far more complex and varied using more realistic models that also consider factors such as the environment prey availability and toxicity levels cost of hunting versus potential reward cost of misidentifying a target and how all these factors might change over time it is possible to create scenarios where at times rarity is selected for instead of against for instance predators might be unwilling to sample unfamiliar prey items if they are rare and the risk for them is high because the potential reward of identifying a new but rare food source would be too low to justify the risk this could result in rare forms being preyed upon very little of course predatory selection is not the only factor that drives evolution sexual selection is another important factor to consider some heliconious butterflies could for instance be shown to prefer rarer forms when mating which would also counteract selection against rarity to some degree so there are many possible ways to explain the diversity among malaria mimics including some we haven't discussed like gene flow and hybridization however pinpointing which of them or which combination of them is actually responsible specifically still requires more research but all of this highlights another problem with malaria mimicry originally malaria mimicry was described as a process of mutual convergence each species evolving to look like the other for the mutual benefit however there seemed to exist many examples of malaria mimics that have evolved seemingly through advergence where one species has become more and more like the other rather than both species meeting in the middle this is for instance what happened in the case of heliconious melpane which seems to have evolved to mimic heliconius eroto cases like this would make malaria mimicry a lot more baitsian in nature and distinguishing the two phenomena a lot harder there are multiple reasons why this might happen different population densities like mentioned before would put a strong selective pressure on the rarer species but a weak selective pressure on the common species the same could be true if one of the species was inconspicuous and the other conspicuous looking or if one species emerged later than the other however while all of these cases would likely result in a large degree of advergent evolution the end result could still be a mutualistic relationship like mueller described or at the very least a common salistic one that still doesn't negatively affect the model however even more problematic is the case when one species is much better defended than the other while the levels of defensiveness are rarely discussed in examples of malaria mimicry in reality they would likely differ to some degree and in some cases quite substantially take these two geometric moths from japan for instance both species sequester unpalatable or poisonous grayonotoxins from their host plants that they feed on during their caterpillar stage however while the left species is a specialist that exclusively feeds on the plants that carry these toxins the right species is a generalist that feeds on multiple different plants as a result they collect much smaller quantities and are presumably far less harmful to their predators this could have important implications for their relationship it could for instance lead to a longer learning period in their predators or to an overall increased attack rate because predators might be willing to make do with mildly unpalatable prey in cases of food shortage not only would this give the less well-defended species a much stronger selective pressure to resemble the better defended species than vice versa it could even result in the less defensive mimics undermining the effectiveness of the warning signal of their more defensive models if this is the case the relationship between the two and other examples like this can no longer even be considered commensalism but would effectively be batesian mimicry even though the mimics have a form of defensiveness themselves this is why classifying cases of malaria mimicry can be a lot harder than its basic definition might suggest and why many biologists have proposed that mimicry should not be separated into two or more distinct evolutionary processes but should rather be seen as a spectrum with batesian and malaria mimicry at each end in any case despite more than a century of progress there is still a lot more to learn about defensive mimicry and how it evolves mimicry is however not only being used for defensive purposes it can similarly be used by predators or parasites to avoid being detected by their prey or their host the wolf in sheep's clothing so to speak of course as with all forms of mimicry aggressive mimics are also not consciously imitating their target mimicry has evolved in these animals because it increases their hunting or parasitism success and thus their biological fitness but where in defense of mimicry it's the predators that are being duped in aggressive mimicry it's the prey how this deception works in detail can however vary quite remarkably from case to case bipolar systems are the simplest example here the model is also the target within the earlier discussed group of batesian ant mimics are several examples particularly among the spiders that use their resemblance to also prey on the ants they mimic the death's head hawk moth a large moth famous for its vaguely skull-shaped pattern on its thorax a feature that has earned them a reputation as a bringer of bad luck misfortune and death mimics bees not only in terms of their appearance but also behaviorally and chemically this allows them to raid beehives for their honey because they smell like honey bees they are chemically invisible and rarely attacked by the worker bees once inside the hive they also produce this unique squeaking noise this noise is thought to mimic the piping sound the queen bees use to calm their workers down female firefly beetles of the genus photores imitate the sexual light signals of other firefly species females to prey on their males they have been shown to be able to attract the males of four different species with distinctively different flash responses that they will adjust according to the male's flash pattern similarly malicious is the spotted predatory katydid which mimics the sexual reply clicks and movements of female cicadas to attract and prey on their males [Music] often however aggressive mimicry systems involve more than two animals many aggressive mimics imitate for instance the prey of their target the monkfish is such an example these fish have a modified dorsal spine that mimics a worm or small shrimp this allows them to hunt more effectively and efficiently by luring their prey into striking distance a similar trick is used by the alligator snapping turtle this ambush predator is very well camouflaged even the inside of its mouth blends in with the surroundings its tongue however bears a conspicuous pink extension that resembles a worm and that it can wiggle around to lure small fish into its mouth but perhaps the most impressive example of this strategy is used by the spider-tailed horn viper they are one of many species of snakes that use their tails as lores but they have truly mastered this hunting strategy the tip of their tail bears a set of conspicuous looking elongated scales and a bulb-like end with this lore which resembles a small spider remarkably well the otherwise perfectly camouflaged snakes are able to attract insect-eating birds with terrifying ease freshwater mollusks of the genus lampcillus also use a particularly impressive form of this strategy the larvae of these mussels are parasitic they must hitch a ride on a fish hose to become adults this is necessary for the sedentary animals to ensure the survival of the species as otherwise the mussels would be slowly washed out of the rivers they live in with every new generation [Music] by using larger fish as taxis they are able to also spread upstream which allowed them to conquer the river habitat transporting the larvae into the fish hosts however is not an easy task for an immobile muscle to increase their chances lambsilis have evolved a cunning way to attract their hosts when the larvae are ready to be released the muscle opens up and begins to display its distinctive mantle flaps that closely resemble the preferred prey of their host this can be a small fish a crayfish a worm or an insect depending on the species the mussels can even wiggle the lore around to sell the illusion of it swimming in the current or walking across the riverbed when a potential host is attracted by this seemingly easy meal and bites the lower the brood pouch bursts releasing a swarm of larvae into the surrounding water and infecting the fish with thousands of parasitic offspring that will grow inside its body until they hop off a few weeks later after developing into juvenile muscles but the prey doesn't necessarily need to be attracted for the mimic to profit it is sufficient for the predator to simply not be identified as a threat the zone-tailed hawk for instance closely resembles the turkey vulture he even accompanies groups of these birds to make himself further inconspicuous because turkey vultures are scavengers their presence doesn't trigger an immediate flight response in the small mammals and birds the hawk preys on this gives him the chance to sneak up on their prey hidden in plain sight yet other mimics resemble a mutualistic symbiont of their target the false cleaner fish for instance is a next to perfect copy of the blue streak cleaner rest a fish that cleans other fish of parasites or dead skin cleaner fish are very appreciated by larger fish and play an important role in maintaining the health of the coral reefs they inhabit how these cleanings take place is actually quite remarkable they tend to happen at specific locations in the reef so called cleaning stations each morning cleaner species such as the rest gather at these locations to perform cleanings for their clients which include anything from sea turtles to groupers sharks and rays many come from far and away to these locations to take advantage of the free service by mimicking these much appreciated fish the false cleaner fish gained protection from predators a form of defensive mimicry but they also abused their resemblance to take easy bites out of the fins of the fish that were hoping for a cleaning because this is not without risk for the much smaller fish they however only seem to resort to this strategy when food is scarce [Music] the blue striped fang blinny another mimic of the cleaner s has an even better trick up its sleeve they are one of only a handful of dynamic mimics in the world a much more famous example is the mimic octopus a basian mimic that has seemingly evolved an innate ability to imitate a whole range of dangerous animals thanks to the ability of octopuses to drastically change both their color and their shape they are able to mimic more than 15 distinct animals such as toxic flatfish sea snails stingrays or sea snakes or the highly venomous lionfish this provides these sand dwelling octopuses with an effective protection when foraging when camouflage is much less effective the fang blenny has similarly the ability to seemingly change its appearance at will to mimic a range of different animals near cleaning stations they often adopt the distinct coloration of the helpful wraths aggressive mimicry to avoid detection by their potential victims however in the absence of clean arrests they usually find other shoals of fish to hide in and adjust their color accordingly a protection against predators most likely while it might not look that convincing to our eyes when you compare the wavelengths reflected by the scales of these fish the impressive resemblance becomes a lot more obvious of all these examples the mimicry of the cleaner rest is however obviously still the most convincing one but of course no video about mimicry would be complete without talking about the common cuckoo these birds are nest parasites instead of going through the trouble of building their own nests breeding the eggs and raising their young they simply lay their eggs in the nest of other bird species and let them do the work to make this unique reproductive strategy even possible cuckoos have evolved many interesting adaptations their belly feathering for instance it seems to mimic the distinctive belly feathering of hawks [Music] experiments could at least show that many small bird species hawks would prey on which are often also the same species the cuckoo parasitizes are fearful of birds with this pattern and flee when they spot it this helps them avoid getting attacked but it unfortunately also allows the cuckoos to access their nests to plant their eggs this alone however doesn't ensure success there is after all no guarantee that the host mother wouldn't simply toss the foreign egg out when she returns to reduce the risk of that happening the cuckoo female removes one of the eggs from the nest herself before she lays her own this ensures that the number of eggs remains the same however even this would likely not work if the cuckoo egg could easily be identified as such but it can't and that's probably the most impressive thing the cuckoo egg mimics the eggs of the host species these are the nests of a meadow pipet a common red start and a reed warbler three of over 40 species regularly parasitized by the cuckoo as you can see in each case the slightly larger cuckoo egg perfectly mimics the eggs of the respective host this egg mimicry actually puzzled biologists for a long time how could the same species of bird in which all individuals should share the same genes produce such a wide variety of egg colors and patterns especially since these are not different subspecies that evolved to a certain degree independently because of their geographic separation like we have seen in previous examples this is all happening in the same area in one tree you might find a red star nest with a blue cuckoo egg and in another tree a meadow pipit nest with a black cuckoo egg in recent years an explanation for this paradox could be found it seems the information for egg coloration is stored on the sex chromosomes more specifically on the y chromosome [Music] sex chromosomes are of course the pair of chromosomes that determine the sex of an animal in mammals for instance males have an x and a y chromosome while females have two x chromosomes this means female eggs which contain one half of the genes will always contain an x chromosome while male sperm will contain either an x or a y in birds it's the other way around with females having the two distinct sex chromosomes and that is the key because each female cuckoo remembers the nest that it was brought up in and will lay her own eggs in the nests of the same species of bird let's say a reed warbler the y chromosome inherited from its mother grandmother great grandmother and so on can look back at a long ancestral history of reed warbler nests likewise the y chromosome of a female cuckoo that was brought up by a red start can look back on a long ancestral history of red star nests however and that's equally as important because males mate with all females in the population and are not separated into different groups neither the x chromosome nor any of the other chromosomes have this property and therefore don't have this uniform ancestral history only the y chromosome is unique in that regard because only it is exclusively inherited by the females this is of course true for the y chromosome in other animals too even ourselves although with swap sexes but because in cuckoos the y chromosome holds the specific genes that control egg coloration and patterns these adaptations can be perfected and evolved differently in different lineages of females allowing for the adaptation to a wide variety of hosts while still keeping the rest of the gene pool uniform and allowing the common cuckoo to persist as a single species but this again only works because of the female's innate behavior to only parasitize the same nests they were brought up in because otherwise natural selection could not favor a particular egg color or pattern in each of the lineages now of course it doesn't always happen as perfectly as that female cuckoos will on occasion make mistakes and lay their eggs in the wrong nests the then conspicuous looking egg will likely be tossed out by the host's parents it is after all very bad for their reproductive success having to raise a chick of a different species especially since cuckoo chicks have the nasty habit of hatching first and pushing all other eggs or even hatchlings out of the nest bird species that have already been exposed to nest mimicry in their evolutionary pest have therefore gotten quite good at identifying foreign eggs bird species that haven't been however for instance because they didn't share a geographic range with the cuckoo because of a vastly different diet or because of an unsuitable nest type would one might expect be bad at identifying cuckoo eggs even if they look conspicuous this was tested by hand placing foreign looking eggs into the nest of various bird species perhaps unsurprisingly insect eaters like the cuckoo is were on average very good at identifying the foreign eggs and tossing them out even species that are not currently being parasitized by the cuckoo seed eaters on the other hand almost always accepted the foreign eggs which indicates that neither they nor their ancestors were exposed to the selective pressure of nest parasitism and therefore didn't evolve the defenses against it this then is presumably how new host species are found when a cuckoo female accidentally lays her egg in a nest of a species of bird that is bad at identifying foreign eggs while at the same time suitable as a host species it might be the beginning of a new lineage of females an example like this can be found in dunks a host species that cuckoos presumably only started to parasitize relatively recently while the female cuckoos of that lineage have clearly not yet evolved to mimic the eggs of the new host species with any convincing degree of accuracy the parents of the species have also not yet evolved the defensive skill to identify the clearly foreign eggs but this will not stay that way forever as the evolutionary arms race between these two animals continues the host species will slowly evolve to better and better spot the false eggs and the cuckoo females will in turn have to evolve to better and better disguise the eggs the only reason the cuckoo can at this point get away with this poor egg mimicry is simply because the arms race between these two species is still relatively new compared to some of the other examples which would and do require much more convincing levels of mimicry to be successful this brings us neatly to the final point arms races like the one between the cuckoo and its hosts are present in all of nature they are a direct result of the process of natural selection and a key aspect of many evolutionary relationships for instance between different animals that share an ecological niche between hosts and parasites between predators and prey and also specifically between mimics and the animals that are being duped by them and in case of batesian mimicry mimics and their models because any advantage gained by batesian mimics would inevitably lead to a weakening of the model's fitness models in batesian mimicry complexes are expected to face a certain degree of selective pressure to evolve away from their mimics back to a more distinct appearance this would lead to a sort of evolutionary chase between the mimic and the model animals that are being duped by mimicry be it aggressive or defensive are similarly expected to evolve to weaken the negative impact of it by improving their ability to detect the deception this would then as we have seen put pressure on the mimic to become more and more convincing all this however of course depends to a large degree on how severely these animals are actually affected by the mimicry and that's a very important point because looking at the many examples discussed here it seems that most mimics seem to be winning their respective evolutionary arms races which might seem odd now ignoring the possibility of a survivorship bias it is actually not that surprising when you simply consider the asymmetry in the cost of failure and the resulting asymmetry in the selective pressure this asymmetry is sometimes described as the rare enemy effect take this group of 20 insect-eating bird species all of these birds hunt in pretty much the same way they will look for insects sitting on flowers rocks leaves or branches and if they spot one they will swiftly attack and try to catch the prey before it has the chance to escape pretty much a typical hunting strategy because of this their insect prey like many other prey animals have evolved a flight response to escape from such predators when they sense danger they will do whatever they can to escape as quickly as possible so they might fly or jump away or simply let themselves fall off the branch they sit on this is an effective strategy against bird attacks however one bird exploits this extinctive behavior the painted red start when foraging it spreads its wings and tail and displays its conspicuous contrasting plumage making itself as noticeable as possible the goal behind this is to spook nearby insects and elicit the same flight response they would use to try to escape other birds and then chase and catch them in the air this impressive exploitation of the insect's defensive strategy is a good example of the rare enemy effect because the painted red start is the only species of the roughly 20 insect-eating birds in their range that hunt in this particular way not only do they exert little selective pressure on the prey to evolve defenses against it it might even be disadvantageous to evolve such defenses given how rare their hunting strategy is compared to the much more common way of hunting against of which fleeing is an effective strategy for the red start on the other hand there was likely a strong selective pressure to perfect this hunting strategy not only did it reduce competition with the other insectivores it also allowed them to exploit a resource in a way done by no other species this selective asymmetry is a good explanation for why many mimics seem to stay ahead of their targets evolutionary speaking like the cuckoo many if not most birds of a population will never encounter a cuckoo but every cuckoo encounters a host moreover even if no bird of that population would be able to spot the false eggs the cost of the parasitism would still be relatively small for the entire population however if no cuckoo would be able to trick its hosts the entire lineage would die out that's why the selective pressure is much higher on the cuckoo than on its hosts and why mimicry is expected to spread through the cuckoo population much faster than rejection does through the host's population because for the cuckoo as a species their survival rests on the ability to do what they do the chisel of natural selection has worked away on its genes much more aggressively than it has on that of its hosts and thus allowed for the evolution of this remarkable way of reproduction and yet the existence of bird species that are rarely if at all used as a host species today but are exceptional at identifying foreign eggs show that there once must have existed lineages of cuckoos parasitizing these birds that for one reason or the other went extinct birds like the great grey shrike which was once a common host of the cuckoo in western europe but for unknown reasons is no longer the same seemed to have happened to blackbirds and song thrushes [Music] all these species are like the survivor of a terrible disease they are now immune to further attacks their ability to identify and reject non-momentic eggs a remnant of their once fierce arms race with the cuckoo makes them very difficult to successfully parasitize again and because having this ability is of little cost for the former hosts this defense against the cuckoo will likely stay with them for hundreds maybe even thousands of years this however doesn't really spell trouble for the cuckoo thanks to their ability to adapt to a wide variety of hosts their population as a whole is not threatened by the loss of one or two lineages especially since they might soon have access to an entire continent of new potential host species likely related to the warming temperatures the cuckoo range seems to be expanding they are now regularly spotted in large parts of siberia and have even been seen in alaska [Music] this is of great concern for the native songbird population while north america has its own nest parasite the cow bird its range doesn't extend all the way north to alaska which means the alaskan bird population is now faced with a completely new type of enemy that they have very little protection against this makes alaska coincidentally the perfect place for the cuckoo to start its invasion of the north american continent and while the arms race on this evolutionary battlefield is only just beginning other battlefields have disappeared the sandhills of north carolina were once home to a poisonous coral snake and its mimic but now only one is left the harmless scarlet king snake for the last 50 years these snakes have been mimicking a ghost the last of the coral snakes in this pine forest disappeared in the 1960s as a consequence what was once an impressive defensive strategy will soon become a burden for the king snake without a model to strike fear into the predators of this forest the colorful warning will become nothing more than an invitation to any predator that spots it for now at least it seems the innate avoidance embedded into the genes of the predators by the previous arms race keeps them at bay but this will only work so long soon predators will begin to learn that hiding behind the scary disguise is now nothing more but a tasty meal and when this happens it will be the beginning of a grim battle for survival and a race against time for the king snake to shed its conspicuous skin as quickly as possible [Music] so you

Channel: Deep Dive

Views: 329,453

Rating: 4.9424419 out of 5

Keywords: Mimicry, animals, Batesian, Mullerian, Nature, Ladybug, Ladybird, Mimic Octopus, Mimic, Biology, Weird Animals, Animal Facts, Evolution, Darwin, Natural Selection, Animals, Nature Documentary, Imposter, Among Us, Science, Documentary, Infographic, Motiongraphic, Animation, Deep Dive

Id: KHxGA6d204I

Length: 53min 5sec (3185 seconds)

Published: Fri Apr 30 2021

Reddit Comments

[u/pbrevis]

This video is outstanding. Extremely well research, beautifully illustrated

[u/XBruceXD]

When the impostor is sus

[u/ainus]

Was Henry Walter Bates a master in his field?

[u/5nackB4r]

I didn't quite understand the true scale of the menace that is Among Us until I saw this thread.

[u/MiltonFriedmeme]

GET OUT OF MY HEAD GET OUT OF MY HEAD GET OUT OF MY HEAD

[u/Jam906]

Red is sus

[u/SighKickYT]

Sus

[u/InstagramNormie_]

this seems kind of similar to a certain 2018 indie multiplayer mobile game 😳😳😳

[u/LifeInHighResolution]

Fascinating.