Biological mimicry occurs when a group of organisms, the mimics, have evolved to share common perceived characteristics with another group, the models, through the selective action of a signal-receiver or dupe. Collectively this is known as a mimicry complex.
The model is usually another species except in cases of automimicry which may involve body parts or developmental stages of the same species. The signal receiver is typically another intermediate organism like the common predator of two species, but may actually be the model itself, such as a moth resembling its spider predator.
Mimicry is in most cases advantageous to the mimic and harmful to the receiver. It may have beneficial, detrimental or no effect on the fitness of the model too, depending on its ecological role with respect to mimic and receiver.
Models themselves are difficult to define in some cases, for example eyespots may not bear resemblance to any specific organism's eyes, and camouflage often cannot be attributed to any particular model.
Many types of mimicry have been described. An overview of each follows, highlighting the similarities and differences between the various forms. Classification is often based on function with respect to the mimic (e.g. avoiding harm), though other parameters can also be used, and multidimensional classifications are required to understand the full picture. For this reason, some cases may belong to more than one class, e.g. automimicry and aggressive mimicry are not mutually exclusive, as one describes the species relationship between model and mimic, while the other describes the function for the mimic (obtaining food). Yet another way of classification is by signaling mode - visual, auditory and olfactory mimicry.
Defensive or protective mimicry takes place when organisms are able to avoid an encounter that would be harmful to them by deceiving an enemy into treating them as something else. Four such cases are discussed here, the first three of which entail mimicry of an aposematic, harmful organism: Batesian mimicry, where a harmless mimic poses as harmful; Müllerian mimicry, where two harmful species share similar perceived characteristics; and Mertensian mimicry, where a deadly mimic resembles a less harmful but lesson-teaching model. Finally, Vavilovian mimicry, where weeds resemble crops, is discussed.
In Batesian mimicry, named after English naturalist Henry Walter Bates, the mimic emits signals similar to the model, but does not possess the attributes that makes it unprofitable to predators (e.g. unpalatability). In other words, a Batesian mimic is a sheep in wolf's clothing. For this reason, it is also known as parasitic mimicry.
- The Ash Borer (Podosesia syringae), a moth of the Clearwing family (Sesiidae), is a Batesian mimic of the Common wasp because it resembles the wasp, but is not capable of stinging. A predator that has learned to avoid the wasp would similarly avoid the Ash Borer.
- The False Cobra (Malpolon moilensis) is a mildly venomous but harmless colubrid snake, which mimics the characteristic "hood" of an Indian cobra's threat display. The Eastern Hognose Snake (Heterodon platirhinos) similarly mimics the threat display of venomous snakes.
- The milk snake resembles the deadly poisonous coral snake.
- Octopuses of the genus Thaumoctopus (the Mimic Octopus and the "wunderpus") are able to intentionally alter their body shape and color so that they resemble dangerous sea snakes or lionfish.
Müllerian mimicry, named after German naturalist Fritz Müller, describes a situation where two or more species have very similar warning or aposematic signals and both share genuine anti-predation attributes (e.g. being unpalatable). This is also known as mutualistic mimicry, but because both species signal honestly, some refer to it as mutual (or Müllerian) resemblance or convergence instead.
- Various bees and numerous vespid and sphecoid wasps: These animals are examples of Müllerian mimics because they have the aposematic yellow and black stripes (sometimes black and red, or black and white). Females of most of these species are potentially harmful to predators, fulfilling the second requirement of Müllerian mimicry. However, in essentially all such species, the males are harmless, and can thus be considered automimics of their conspecific females (see below). There are also many genera in these groups where the females are not capable of stinging, and yet still possess aposematic coloration (e.g., the wasp genus Cerceris), so they are considered Batesian mimics.
Emsleyan or Mertensian mimicry, named after M. G. Emsley and German herpetologist Robert Mertens, describes unusual cases where deadly prey mimic a less dangerous species. If there is some other species that is harmful but not deadly as well as aposematic, the predator may learn to recognize its particular warning colors and avoid such animals. A deadly species will then profit by mimicking the less dangerous aposematic organism, if this results in fewer attacks than camouflage would.
- Some Milk Snake (Lampropeltis triangulum) subspecies (harmless), the moderately toxic False Coral Snakes (genus Erythrolamprus), and the deadly Coral Snakes all have a red background color with black and white/yellow stripes. In this system, both the milk snakes and the deadly coral snakes are mimics, whereas the false coral snakes are the model.
Wasmannian mimicry, named after E. Wasmann, refers to cases where the mimic resembles a model along with which it lives (as an inquiline) in a nest or colony. Most of the models here are social insects such as ants,termites, bees and wasps.
Mimetic weeds (Vavilovian mimicry)
Vavilovian mimicry, named after Russian botanist and geneticist Nikolai Vavilov, describes weeds which share characteristics with a plant that was domesticated through artificial selection. Selection against the weed may occur either by manually eradicating it, or by separating its seeds from those of the crop. The latter process, known as winnowing, can be done manually or by a machine. Vavilovian mimicry presents an illustration of unintentional (or rather 'anti-intentional') selection by man. While some cases of artificial selection go in the direction desired, such as selective breeding, this case presents the opposite characteristics. Weeders do not want to select weeds that look increasingly like the cultivated plant, yet there is no other option. A similar agricultural problem occurs with adaptations to pesticides. Vavilovian mimics may eventually be domesticated themselves, and Vavilov called these weeds-turned-crops secondary crops.
Aggressive mimicry describes predators (or parasites) which share characteristics with a species hamrless to their prey (or host), allowing them to avoid detection by the latter. It is also sometimes referred to as Peckhamian mimicry after George and Elizabeth Peckham. The mimic may resemble the prey or host itself, or another organism, which is either neutral or beneficial to the signal receiver. In this class of mimicry, the model may be affected negatively, positively or not at all. Just as parasites can be treated as a form of predator, host-parasite mimicry is treated here as a subclass of aggressive mimicry.
Reproductive mimicry occurs when the actions of the dupe directly aid in the mimic's reproduction. This is common in plants, which may have deceptive flowers that do not provide the reward they would seem to signal to pollinating insects. Other forms of mimicry have a reproductive component, such as Vavilovian mimicry involving seeds, and brood parasitism, which also involves aggressive mimicry.
Automimicry or intraspecific mimicry occurs within a single species, one case being where one part of an organism's body resembles another part. Examples include snakes in which the tail resembles the head and show behavior such as moving backwards to confuse predators and insects and fishes with eyespots on their hind ends to resemble the head. The term is also used when the mimic imitates other morphs within the same species.
Biomimicry is the application of biological methods, systems and design principles to the study and design of engineering systems and modern technology, often in an attempt to optimize resource use. The term is often used synonymously with biomimetics, biognosis, bionics, or bionical creativity engineering, though the overlap is not total: Bionics, for instance, refers to the flow of concepts from biology to engineering and vice versa. Hence, there are two slightly different points of view regarding the meaning of the word.
The transfer of technology between life forms and synthetic constructs is, according to proponents of bionic technology, desirable because evolutionary pressure typically forces living organisms, including fauna and flora, to become highly optimized and efficient.
Often, the study of bionics emphasizes implementing a function found in nature rather than just imitating biological structures. For example, in computer science, cybernetics is concerned with modeling the feedback and control mechanisms inherent in intelligent behavior, while artificial intelligence comprises basically any model of intelligence, irrespective of a particular implementation.
Roughly, we can distinguish three biological levels in the fauna or flora, after which technology can be modeled:
- Mimicking natural methods of manufacture (example: a spider's silk)
- Imitating mechanisms found in nature (example: hook-and-loop fasteners)
- Studying organizational principles from social behavior of organisms, such as the flocking behavior of birds, the foraging behavior of bees and ants, and the swarm intelligence-based behavior of a school of fish.
Examples of biomimetics
- A classical example is the development of dirt- and water-repellent paint (coating) from the observation (the lotus effect) that the surface of the lotus flower plant is practically un-sticky for any aqueous solution. Some paints and roof tiles have been engineered to be self-cleaning by copying the mechanism from the Nelumbo lotus.
- Hulls of boats imitating the thick skin of dolphins.
- Sonar, radar, and medical ultrasound imaging imitating the echolocation of bats.
- In the field of computer science, the study of bionics has produced artificial neurons, artificial neural networks, and swarm intelligence.
- Velcro is the most famous example of biomimetics. In 1948, the Swiss engineer George de Mestral was cleaning his dog of burrs picked up on a walk when he realized how the hooks of the burrs clung to the fur.
- Cat's eye reflectors were invented by Percy Shaw in 1935 after studying the mechanism of cat eyes. He had found that cats had a system of reflecting cells, known as tapetum lucidum, which was capable of reflecting even very low intensities of light.
- The wing structure of the blue morpho butterfly was studied and the way it reflects light was mimicked to create an RFID tag that can be read through water and on metal.
- Synthetic or "robotic" vegetation, which aids in conservation and restoration, are machines designed to mimic many of the functions of living vegetation, e.g. light absorptino or CO2 sequestration.
- Medical adhesives involving glue and tiny nano-hairs are being developed based on the physical structures found in the feet of geckos.
In medicine, bionics means formeostly the replacement or enhancement of organs or other body parts by mechanical versions. Bionic implants differ from mere prostheses by mimicking the original function very closely, or even surpassing it.
While the technologies that make bionic implants possible are still in a very early stage, a few bionic items already exist, the best known being the cochlear implant, a device for deaf people. Other examples include hand prostheses or artificial hearts.
- Biomimicry Institute
- Lecture notes from BIOL 2007 (University College London) - WARNING COLOUR AND MIMICRY
- Centre for Biomimetics at the University of Reading
- Mimicry and the Monte Carlo predator: the palatability spectrum, and the origins of mimicry, Biological Journal of the Linnean Society, Volume 23 Issue 2-3, Pages 247 - 268
- Industrial ecology: shedding more light on its perspective of understanding nature as model, Sustainable Development, Volume 11 Issue 3, Pages 143 - 158
- Engineering role models: do non-human species have the answers? Ecological Engineering, Volume 20, Issue 5, October 2003, Pages 379-387, The Philosophy and Energence of Ecological Engineering