Projectile use by living systems
Although projectile
A projectile is any object projected into space by the exertion of a force. Although a thrown baseball is technically a projectile too, the term more commonly refers to a weapon....

s are commonly used in human conflict, projectile use by living systems other than humans is relatively rare.

Liquid projectiles

Most projectiles used by animals are liquids. Among invertebrates there are a number of examples. Velvet worm
Velvet worm
The velvet worms are a minor ecdysozoan phylum. These obscurely segmented organisms have tiny eyes, antennae, multiple pairs of legs and slime glands. They have variously been compared to worms with legs, caterpillars and slugs...

s can fire a sticky fluid which they use to trap their prey. The fluid is fired from glands on the sides of their head. The spitting spider
Spitting spider
Spitting spiders are members of the family Scytodidae. There are several genera, of which Scytodes is the best-known. Over 150 species of scytodids have been described worldwide....

s Scytodes
Scytodes is a genus of spitting spider that occurs all around the world. The best known species is Scytodes thoracica which has a holarctic distribution....

 can spit a venomous and sticky fluid that traps its victims and also poisons them The bombardier beetle
Bombardier beetle
Bombardier beetles are ground beetles in the tribes Brachinini, Paussini, Ozaenini, or Metriini—more than 500 species altogether—which are most notable for the defense mechanism that gives them their name: When disturbed, the beetle ejects a noxious chemical spray in a rapid burst of pulses from...

 is unusual by using a violent exothermic
In thermodynamics, the term exothermic describes a process or reaction that releases energy from the system, usually in the form of heat, but also in the form of light , electricity , or sound...

 chemical reaction to launch a boiling noxious chemical spray in a rapid burst of pulses from special glands in its abdomen, accompanied with a popping sound. The oogpister beetle will fire formic acid
Formic acid
Formic acid is the simplest carboxylic acid. Its chemical formula is HCOOH or HCO2H. It is an important intermediate in chemical synthesis and occurs naturally, most notably in the venom of bee and ant stings. In fact, its name comes from the Latin word for ant, formica, referring to its early...

 at attackers, probably extracting the formic acid from the ants that it eats. The devil-rider stick insects (Anisomorpha
Anisomorpha is a genus of walking stick insect capable of secreting a substance from glands on the metathorax that can cause an intense burning irritation of the eyes and mouth of potential predators on contact. Species are found throughout the mainland Central, northern South America, and the...

) can fire turpines from glands on the metathorax that can cause an intense burning irritation of the eyes and mouth of potential predators on contact. Wood ants will spray acid at attackers. A type of planthopper
A planthopper is any insect in the infraorder Fulgoromorpha within the Hemiptera. The name comes from their remarkable resemblance to leaves and other plants of their environment and from the fact that they often "hop" for quick transportation in a similar way to that of grasshoppers. However,...

 of Madagascar
The Republic of Madagascar is an island country located in the Indian Ocean off the southeastern coast of Africa...

 is able to flick small balls of honeydew
Honeydew (secretion)
Honeydew is a sugar-rich sticky liquid, secreted by aphids and some scale insects as they feed on plant sap. When their mouthpart penetrates the phloem, the sugary, high-pressure liquid is forced out of the gut's terminal opening. Honeydew is particularly common as a secretion in the Hemipteran...

, this attracts day geckos that feed on the honeydew and whose presence may deter predators from approaching the sap-sucking insect

A number of vertebrates also use liquid projectiles. The archer fish will squirt water from its mouth to dislodge invertebrates from overhanging branches. Some diptodactyline
Diplodactylinae is the second largest subfamily of Gekkonidae by number of species . There are 142 species in seventeen genera...

Geckos are lizards belonging to the infraorder Gekkota, found in warm climates throughout the world. They range from 1.6 cm to 60 cm....

s can fire a black or pale yellow sticky fluid out of glands in their tail, for a distance of about a meter, and with good aim. This fluid has a musky unpleasant odour and although it isn't toxic it may discourage predators, in particular the big arthropods that prey on these geckos Spitting cobra
Spitting cobra
A spitting cobra is one of several species of cobras that have the ability to eject venom from their fangs when defending themselves against predators. The sprayed venom is harmless to intact skin...

 can squirt venom from forward-facing holes in its fangs It aims for the eyes, spitting up to 1.5m. The venom may cause blindness. The Mangshan pitviper is also reported to spit venom.

A bird that uses liquid projectiles in defense is the Southern Giant Petrel
Southern Giant Petrel
The Southern Giant Petrel , also known as the Antarctic Giant Petrel, Giant Fulmar, Stinker, and Stinkpot, is a large seabird of the southern oceans. Its distribution overlaps broadly with the similar Northern Giant Petrel, though it overall is centered slightly further south...

 which produces a stomach oil made up of wax esters and triglycerides that is stored in the proventriculus and can be projectile vomited on predators. Some species of penguin
Penguins are a group of aquatic, flightless birds living almost exclusively in the southern hemisphere, especially in Antarctica. Highly adapted for life in the water, penguins have countershaded dark and white plumage, and their wings have become flippers...

 expel liquid feces in a projectile manner, to a distance of up to about 50 cm. They are believed to do this because during the brooding season, when penguins are sitting on their nests, they avoid leaving their nests and thereby leaving their eggs open to predation and thus to maintain a clean nest they evolved the ability to project their feces

Among mammals, skunk
Skunks are mammals best known for their ability to secrete a liquid with a strong, foul odor. General appearance varies from species to species, from black-and-white to brown or cream colored. Skunks belong to the family Mephitidae and to the order Carnivora...

s can eject a noxious fluid from glands near their anus. It is not only foul smelling, but can cause skin irritation and, if it gets in the eyes, temporary blindness. Camel
A camel is an even-toed ungulate within the genus Camelus, bearing distinctive fatty deposits known as humps on its back. There are two species of camels: the dromedary or Arabian camel has a single hump, and the bactrian has two humps. Dromedaries are native to the dry desert areas of West Asia,...

s will bring up their stomach contents, along with saliva, and project it out towards whatever the camel assesses is threatening in order distract, surprise, or bother the threat

Solid projectiles

Some New-world tarantulas have a dense covering of hairs called urticating hairs on the abdomen that they sometimes use as protection against enemies . Species with urticating hairs can kick these hairs off: they are flicked into the air at a target using their back pairs of legs . These fine hairs are barbed and designed to irritate and can be lethal to small animals such as rodents. The symptoms range from species to species, from person to person, from a burning itch to a minor rash, from being lethal to simply being a deterrent. With humans, they can cause irritation to eyes, nose, and skin, and more dangerously, the lungs and airways, if inhaled. In some cases, tarantula hairs have caused permanent damage to human eyes. Urticating hairs do not grow back, but are replaced with each moult. Another invertebrate, the antlion
Antlions are a group of insects in the family Myrmeleontidae . The most well-known genus is Myrmeleo. There are about 2,000 species...

, also makes use of solid projectiles. The antlion lies at the bottom of a sloping pit that it digs in the sand. Small prey slip into the pit on the loose substrate. If the prey crawls up the slopes of the pit, the antlion throws sand at the prey, which may dislodge it and send it back down the pit.

A number of vertebrate species also make use of solid projectiles. Among birds the hornbill
Hornbills are a family of bird found in tropical and subtropical Africa, Asia and Melanesia. They are characterized by a long, down-curved bill which is frequently brightly-colored and sometimes has a casque on the upper mandible. Both the common English and the scientific name of the family...

 uses projectile motion in eating food. The hornbill's beak typically only contacts at the tip, and it has a short tongue. To swallow food the hornbill instead throws the food from the tip of its long bill backwards into the throat One example of solid projectile use among mammals is the California Ground Squirrel
California Ground Squirrel
The California ground squirrel , is a common and easily observed ground squirrel of the western United States and the Baja California peninsula; it is common in Oregon and California and its range has relatively recently extended into Washington and northwestern Nevada...

, which is known to distract predators such as the rattlesnake
Rattlesnakes are a group of venomous snakes of the genera Crotalus and Sistrurus of the subfamily Crotalinae . There are 32 known species of rattlesnake, with between 65-70 subspecies, all native to the Americas, ranging from southern Alberta and southern British Columbia in Canada to Central...

 and gopher snake from locating their nest burrow
A burrow is a hole or tunnel dug into the ground by an animal to create a space suitable for habitation, temporary refuge, or as a byproduct of locomotion. Burrows provide a form of shelter against predation and exposure to the elements, so the burrowing way of life is quite popular among the...

s by kicking sand into their eyes.. A wild female African elephant has also been observed to throw various material at an interfering rhino Orca
The killer whale , commonly referred to as the orca, and less commonly as the blackfish, is a toothed whale belonging to the oceanic dolphin family. Killer whales are found in all oceans, from the frigid Arctic and Antarctic regions to tropical seas...

s have been observed to throw seal prey using their tail flukes in apparent play behaviour Some primates, including human
Humans are the only living species in the Homo genus...

s, can throw objects such as rocks, sticks, and feces as projectiles. Primates that can throw are humans, bonobo
The bonobo , Pan paniscus, previously called the pygmy chimpanzee and less often, the dwarf or gracile chimpanzee, is a great ape and one of the two species making up the genus Pan. The other species in genus Pan is Pan troglodytes, or the common chimpanzee...

s, chimpanzee
Chimpanzee, sometimes colloquially chimp, is the common name for the two extant species of ape in the genus Pan. The Congo River forms the boundary between the native habitat of the two species:...

s, gorilla
Gorillas are the largest extant species of primates. They are ground-dwelling, predominantly herbivorous apes that inhabit the forests of central Africa. Gorillas are divided into two species and either four or five subspecies...

s, orang-utans capuchins, certain gibbon
Gibbons are apes in the family Hylobatidae . The family is divided into four genera based on their diploid chromosome number: Hylobates , Hoolock , Nomascus , and Symphalangus . The extinct Bunopithecus sericus is a gibbon or gibbon-like ape which, until recently, was thought to be closely related...

s and perhaps some baboon
Baboons are African and Arabian Old World monkeys belonging to the genus Papio, part of the subfamily Cercopithecinae. There are five species, which are some of the largest non-hominoid members of the primate order; only the mandrill and the drill are larger...

s and Japanese macaque
Japanese Macaque
The Japanese macaque , historically known as saru , but now known as Nihonzaru to distinguish it from other primates, is a terrestrial Old World monkey species native to Japan....

s (although not rhesus macaques A chimpanzee
Chimpanzee, sometimes colloquially chimp, is the common name for the two extant species of ape in the genus Pan. The Congo River forms the boundary between the native habitat of the two species:...

 in a Swedish zoo was observed to stockpile stones to be used as missiles against visitors Humans have developed projectile-launching devices such as bow
Bow (weapon)
The bow and arrow is a projectile weapon system that predates recorded history and is common to most cultures.-Description:A bow is a flexible arc that shoots aerodynamic projectiles by means of elastic energy. Essentially, the bow is a form of spring powered by a string or cord...

s, gun
A gun is a muzzle or breech-loaded projectile-firing weapon. There are various definitions depending on the nation and branch of service. A "gun" may be distinguished from other firearms in being a crew-served weapon such as a howitzer or mortar, as opposed to a small arm like a rifle or pistol,...

s, and rocket
A rocket is a missile, spacecraft, aircraft or other vehicle which obtains thrust from a rocket engine. In all rockets, the exhaust is formed entirely from propellants carried within the rocket before use. Rocket engines work by action and reaction...


Tethered projectiles

Chameleons are a distinctive and highly specialized clade of lizards. They are distinguished by their parrot-like zygodactylous feet, their separately mobile and stereoscopic eyes, their very long, highly modified, and rapidly extrudable tongues, their swaying gait, the possession by many of a...

s, frog
Frogs are amphibians in the order Anura , formerly referred to as Salientia . Most frogs are characterized by a short body, webbed digits , protruding eyes and the absence of a tail...

s and some lungless salamander
Lungless salamander
The Plethodontidae, or Lungless salamanders, are a family of salamanders. Most species are native to the western hemisphere, from British Columbia to Brazil, although a few species are found in Sardinia, Europe south of the Alps, and South Korea...

s have tongue
The tongue is a muscular hydrostat on the floors of the mouths of most vertebrates which manipulates food for mastication. It is the primary organ of taste , as much of the upper surface of the tongue is covered in papillae and taste buds. It is sensitive and kept moist by saliva, and is richly...

s that act like a tethered projectile. In frogs, the tongue is attached at the front of the mouth and rotates about this attachment as it flips out (thus the top of the tongue at rest becomes the bottom when extended). In chameleons, the tongue contracts against a tapered hyoid bone, eventually slipping off and projecting forward at very high speed. Lungless salamanders use a similar method, however, both the tongue and underlying hyoid bone project (in contrast to chameleons, whose hyoid remains fixed while the fleshy portion of the tongue projectes). In both salamanders and chameleons, the movement is too fast and requires too much mechanical power for muscle alone to provide - instead, muscles slowly pre-load elastic elements such as connective tissue, which can then recoil and release the stored energy at a much higher rate. In order to retract their tongues over such great distances, the tongue muscles of chameleons have perforated Z-disks, allowing each sarcomere
A sarcomere is the basic unit of a muscle. Muscles are composed of tubular muscle cells . Muscle cells are composed of tubular myofibrils. Myofibrils are composed of repeating sections of sarcomeres, which appear under the microscope as dark and light bands...

 to shorten far greater distances than those of other vertebrates.


The pistol shrimp claw has a pistol-like feature made of two parts. A joint allows the "hammer" part to move backward into a right-angled position. When released, it snaps into the other part of the claw, emitting an enormously powerful wave of bubbles capable of stunning larger fish and breaking small glass jars.

Plants and fungi

The seed
A seed is a small embryonic plant enclosed in a covering called the seed coat, usually with some stored food. It is the product of the ripened ovule of gymnosperm and angiosperm plants which occurs after fertilization and some growth within the mother plant...

 pods of the Orange Jewelweed have projectile seeds that, if ripe, explode out of the pods when they are lightly touched. The seed pods of the scotch broom also burst open, often with an audible crack, projecting the seeds from the parent plant. Some plants such as the Dogwood Bunchberry and white mulberry
White Mulberry
Morus alba, known as white mulberry, is a short-lived, fast-growing, small to medium sized mulberry tree, which grows to 10–20 m tall. The species is native to northern China, and is widely cultivated and naturalized elsewhere...

 will also fling pollen
Pollen is a fine to coarse powder containing the microgametophytes of seed plants, which produce the male gametes . Pollen grains have a hard coat that protects the sperm cells during the process of their movement from the stamens to the pistil of flowering plants or from the male cone to the...

 from their flowers. Peat mosses are known to explosively launch their spores

Hat-throwing fungi
Pilobolus crystallinus
Pilobolus crystallinus var. crystallinus, commonly known as the "Dung Cannon" or "Hat Thrower", is a species of fungus belonging to the Mucorales order. It is unique in that it adheres its spores to vegetation, so as to be eaten by grazing animals. It then passes through the animals' digestive...

fire their spore capsules up to 2m.

External links

Natures Marksmen - a video showing projectile use by archer fish and velvet worms
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