Swarm
From Wikipedia, the free encyclopedia
The term swarm can be applied to fish, insects, birds as well as various microorganisms, such as bacteria, and describes a behaviour of an aggregate of animals of similar size and body orientation, generally moving in the same direction. Group size is a major aspect of the social environment of participants.
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[edit] Bees
The swarming of honey bees refers to the reproductive action of an entire colony of bees, as opposed to the reproduction of single bees; see queen bee and honey bee life cycle.
[edit] Ants
[edit] Termites
In many cultures, termites are used for food, particularly the alates. The alates are nutritious, having a good store of fat and protein, and are palatable in most species with a nutty flavour when cooked. They are easily gathered at the beginning of the rainy season in West, Central and Southern Africa when they swarm, as they are attracted to lights and can be gathered up when they land on nets put up around a lamp. The wings are shed and can be removed by a technique similar to winnowing. They are best gently roasted on a hot plate or lightly fried until slightly crisp; oil is not usually needed since their bodies are naturally high in oil.
[edit] Locusts
The term locust refers to the swarming phase of the short-horned grasshoppers of the family Acrididae. The origin and apparent extinction of certain species of locust—some of which reached 6 inches (15 cm) in length—are unclear.[1]
These are species that can breed rapidly under suitable conditions and subsequently become gregarious and migratory. They form bands as nymphs and swarms as adults—both of which can travel great distances, rapidly stripping fields and greatly damaging crops.
Charles Valentine Riley, Norman Criddle and Sir Boris Petrovich Uvarov, were involved in the understanding and destructive control of the locust. Research at Oxford University has identified that swarming behaviour is a response to overcrowding. Increased tactile stimulation of the hind legs causes an increase in levels of serotonin.[2] This causes the locust to change color, eat much more, and breed much more easily. The transformation of the locust to the swarming variety is induced by several contacts per minute over a four-hour period.[3] It is estimated that the largest swarms have covered hundreds of square miles and consisted of many billions of locusts.
The extinction of the Rocky Mountain locust has been a source of puzzlement. Recent research suggests that the breeding grounds of this insect in the valleys of the Rocky Mountains came under sustained agricultural development during the large influx of gold miners,[1] destroying the underground eggs of the locust.[4] [5].
In a paper in the 2009-01-30 edition of the AAAS magazine Science, Anstey & Rogers et al. showed that when desert locusts meet up, their nervous systems release serotonin, which causes them to become mutually attracted, a prerequisite for swarming.[6][7]
[edit] Fish
Shoal can describe any group of fish, including mixed-species groups, "school" is reserved for more closely knit groups of the same species swimming in a highly synchronized and polarized manner.
Fish derive many benefits from shoaling behaviour including defense against predators (through better predator detection and by diluting the chance of capture), enhanced foraging success, and higher success in finding a mate. It is also likely that fish benefit from shoal membership through increased hydrodynamic efficiency.
Fish use many traits to choose shoalmates. Generally they prefer larger shoals, shoalmates of their own species, shoalmates similar in size and appearance to themselves, healthy fish, and kin (when recognized).
The "oddity effect" posits that any shoal member that stands out in appearance will be preferentially targeted by predators. This may explain why fish prefer to shoal with individuals that resemble them. The oddity effect would thus tend to homogenize shoals.
One puzzling aspect of shoal selection is how a fish can choose to join a shoal of animals similar to themselves, given that it cannot know its own appearance. Experiments with zebrafish have shown that shoal preference is a learned ability, not innate. A zebrafish tends to associate with shoals that resemble shoals in which it was reared (that is, a form of imprinting).
Other open questions of shoaling behaviour include identifying which individuals are responsible for the direction of shoal movement. In the case of migratory movement, most members of a shoal seem to know where they are going. In the case of foraging behaviour, ethologist Stephan Reebs, writing in the journal Animal Behaviour, reported that captive shoals of golden shiner (a kind of minnow) were led by a small number of experienced individuals who knew when and where food was available.[8]
[edit] Other marine animals
Small marine animals, such as copepods, can also swarm under certain conditions. Antarctic krill, small shrimp-like crustaceans live in large swarms, sometimes reaching densities of 10,000–30,000 individual animals per cubic meter.[9]
Jellyfish are also said to "swarm".
Large marine mammals, such as whales, dolphins and dolphins, also form social groups called pods, but perhaps short of what would be called a "swarm".
[edit] Other examples
Mosquitoes: Adult mosquitoes usually mate within a few days after emerging from the pupal stage. In most species, the males form large swarms, usually around dusk, and the females fly into the swarms to mate.
[edit] See also
[edit] References
- ^ a b Encarta Reference Library Premium 2005 DVD. Article — Rocky Mountain Locust.
- ^ BBC News | Locust swarms 'high' on serotonin
- ^ Mechanosensory-induced behavioural gregarization in the desert locust Schistocerca gregaria
- ^ Ryckman, Lisa Levitt (1999-06-22). "The Great Locust Mystery". Rocky Mountain News. http://www.denver-rmn.com/millennium/0622mile.shtml. Retrieved on 2007-05-20.
- ^ Lockwood, Jeffrey A. Locust: The Devastating Rise and Mysterious Disappearance of the Insect that Shaped the American Frontier
- ^ The Key to Pandora's Box, AAAS Science, 2009-01-30, P.A. Stevenson (Leipzig University), accessed 2009-01-31
- ^ Blocking 'happiness' chemical may prevent locust plagues, New scientist, 2009-01-29, accessed 2009-01-31
- ^ Reebs, S.G. 2000. Can a minority of informed leaders determine the foraging movements of a fish shoal? Animal Behaviour 59: 403-409.
- ^ Hamner, W. M., Hamner, P. P., Strand, S. W., Gilmer, R. W. (1983). "Behavior of Antarctic Krill, Euphausia superba: Chemoreception, Feeding, Schooling and Molting'". Science 220: 433–435. doi:. PMID 17831417.
[edit] External links
- New York times article on investigations into swarming
- Christian Jacob, Ph.D — swarm computer simulation
- Lessons from Mother Nature on How to Manage Traffic — Daily Planet on Discovery Channel
