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Many symbiotic relationships take place intimately inside a body; Lichens are one example.This interior symbiosis is called endosymbiosis. Endo- means inside. These relationships persist in time.

Many other symbiotic partnerships take place intimately on the surface of one partner's body. This is called ectosymbiosis. Ecto- means outside. These relationships also persist through time.

Still other symbioses take place because of partners behaving in ways that brings them together to accomplish mutual benefit. This is called behavioral symbiosis. Pollination of flowers by insects is an example. Contact between partners may be brief, and only once a year. Or contact may be regular.

Note: Some "behavioral symbioses" often given as examples are in truth marvelous examples of interliving and interdependence. For example, a hermit crab lives in the shell of a dead snail. The crab's body has evolved a twisted abdomen, pink and without protection, so it must live in a snail shell of the correct size, but there is no active partnership between living organisms here. But, for the sake of simplicity, and for present purposes, let's call such relationships a kind of symbiosis anyway. Hermit crabs are alert to newly available shells, (that is, recently dead mollusks) and must compete for them. Of course, each time a hermit crab switches up to a larger shell, its previous shell becomes available to other hermits.

A Gallery of Behavioral Symbiosis

The largest kind of behavioral symbiosis on Earth is Plant Pollination. Go here to explore pollination in depth. Below are a few examples of behavioral symbiosis. Since scientific interest in these associations is fairly recent, there are undoubtedly many more that have not yet been noticed or studied. Ironically, indigenous peoples know of many common behavioral symbioses that civilizations have forgotten, so new discoveries are sometimes new recoveries.


The watchman goby and the little pistol shrimp are inseparable companions.They are both small prey animals. The shrimp has very poor eyesight, and when out of the burrow keeps an antenna in contact with the goby. The fish flicks its tail to warn the shrimp of predators. The shrimp excavates the long burrow in the sands where they both take cover from predators. This may be a kind of optional symbiosis; either might survive without it, but are more likely to live longer with it.

Nutrition and Protection

This little jumping spider, Psecas chapoda, lives strictly associated with the terrestrial bromeliad Bromelia balsanae (below). The droppings of the spider contribute 18% of the plant's total nitrogen. In a field experiment, spider presence resulted in leaves 15% longer than in plants without symbiote spiders. Several animal species live in strict association with bromeliad rosettes, and it is likely that they are symbiotes of the bromeliads as well.

Communicative Nutrition

On coral reefs, two predators of different species hunt cooperatively. The grouper is best at open water hunting. The moray can fit into crevices where prey can hide. A grouper goes to the lair of a giant moray eel (up to ten feet long), headstands, and gives a deliberate head shake, as if to say, "Let's hunt." The eel leaves its den and off they swim, side by side. The grouper often leads the giant eel to a crevice where the grouper's prey is hiding. In a Red Sea study, Groupers and morays caught almost five times more prey through mutual hunting than when hunting solo. Morays hunt most often at night, groupers during day. Theirs is the first association found between species where a deliberate communication signal is used.


The honeyguide bird is well known to lead larger animals with a sweet tooth to a wild beehive the bird has found. The ratel or honey badger is one partner in this facultative (by choice) symbiosis. Humans are the most common partner, and no doubt have been for many thousands of years. The honeyguide flutters and cries and flies in the hive direction until both bird and symbiote arrive at the hive. The partner breaks into the hive, gathers its fill, and the bird fills up on leftover comb, eating honey, bee larvae, waxworms (hive parasites), and beeswax. Honeyguide Image credit Nick Bray
The band-rumped storm petrel, Oceanodroma castro, has developed a serial nest-burrow kind of symbiosis. One pair inhabits the burrow half the year, another pair the same burrow the other months, like time-shared condos. This split into two populations, one breeding in winter, one in summer, has been going on for thousands of years, so long that the groups differ genetically as well as behaviorally. Darwin asserted long ago that two species could emerge from one in the
same physical location. This claim has been disputed, but this little petrel has proven Darwin correct. Time is the feature separating two populations.
The female senita moth is the obligate pollinator of the senita cactus of the Sonoran desert of North America. She actively pollinates the flower, then lays her eggs in the flower ovary. The hatched larvae do eat about 30% of the developing seeds, but plenty survive to insure the cactus reproduction. A very similar obligate symbiosis, also in a desert biome, is between yucca plants and their pollinator, the yucca moth, which rolls threads of pollen into a ball, then carefully places the ball into the cup-shaped stigma. Like the senita moth, she then lays her eggs in the ovary, with similar results. Forty species of yucca depend on one kind of moth.

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Cleaning Symbiosis Land and Sea

A common kind of behavioral symbiosis is Cleaning. Animals on both land and in the sea attract ecto-parasites (on skin). Parasites and dead skin make good food for other animals, which has led to behavioral associations that benefit both partners. On land, these partnerships are best known between birds and grazing animals. In the ocean, they are best known at "cleaning stations" on coral reefs. The examples below are a small sample; many such exist, and no doubt many have not yet been noticed.

A green sea turtle is cleaned by several fish. Many species of fish act as cleaners, in groups and alone. Reefs can be a sort of day-spa for turtle health and pleasure.

A sea turtle is cleaned by a cloud of tangs eager for food. Photo courtesy of Ellen Husain

The capybara of South America is cleaned by a bird.
A school of grunts gape wide for
teeth cleaning by a juvenile wrasse
cattle egrets at the local tick restaurant
an impala has her ear cleaned by an oxpecker bird
A warthog lolls in bliss while a mongoose family carefully check her for parasites.
Image courtesy Jerry Haig, A Glasgow Vet in Africa
cowbirds find pickings on a North American bison
A cleaner shrimp is the dental hygenist for a moray eel
a pair of wrasses work the long body of a pipefish
a flock of oxpeckers prepare to work on a cape buffalo

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Phoresis: Hitchhike Symbiosis

Many short-term behavioral assiociations are for traveling. But some hitchhikers commit to long term associations.

the gray mite on the burying beetle's wing-covers travels with it from carcass to carcass. Flies arrive first and lay eggs. Beetles arrive next, and the mites jump off to eat fly eggs. Both mite and beetle benefit. Image by John Caddy
A hermit crab has covered its shell home with small sea anemones. The crab gains protection, and the anemones gain more flow to carry food their way.
photo copyright © Malcom Nobbs
a camouflaged imperator shrimp rides a nudibranch
a crab carries a fire urchin for protection
an imperator shrimp travels on a nudibranch
an imperator shrimp travels on a sea cucumber

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Explore Symbiosis