The plover bird and the crocodile have an ancient symbiotic relationship that has been observed for centuries. This unique interspecies interaction has spawned folk tales and legends across many cultures that tell the story of how the plover bird helps the crocodile by cleaning its teeth, and in return, the crocodile refrains from attacking the bird.
What is the plover bird?
The plover bird is a type of wading shorebird found in wetlands and coastal areas around the world. There are several different species of plover, but the Egyptian plover is most famously known for its relationship with the Nile crocodile. The Egyptian plover (Pluvianus aegyptius) is a relatively small plover, around 9 inches long with grayish-brown plumage on its back and wings, and white underparts. It has a long, slender black bill adapted for probing and picking small prey.
Plovers are adept at stealthily walking along muddy shorelines and stealthily moving through vegetation. Their diet consists mainly of invertebrates like insects, worms, and mollusks which they capture with precision strikes of their beak. Plovers employ a run-and-peck foraging strategy, making short quick runs and pecking at their prey. Their cryptic plumage allows them to blend into their surroundings and avoid predation.
The Egyptian plover is native to sub-Saharan Africa and lives in proximity to large bodies of water where crocodiles dwell. They build simple scrape nests on the ground lined with grasses and stones near riverbanks. Plover pairs exhibit strong territoriality over their nesting sites and breeding grounds.
What is the crocodile?
Crocodiles are large, semiaquatic reptiles that live throughout the tropics in Africa, Asia, the Americas and Australia. They are members of the order Crocodilia, which also includes alligators and caimans.
Crocodiles are ambush predators, waiting motionless in the water for prey to come within striking distance. They primarily hunt fish, birds, mammals and other reptiles. Their slender snouts are lined with sharp conical teeth used for seizing and tearing prey. On land they can lunge short distances to grab prey. Their jaws exert tremendous bite force, enabling them to crush bones and turtle shells.
Nile crocodiles are one of the largest crocodile species. They can grow over 16 feet long and weigh up to 1,650 pounds. Males are significantly larger than females. Nile crocodiles live in freshwater habitats like rivers, lakes and marshes throughout sub-Saharan Africa. They are apex predators in their ecosystems. Their skin is plated with thick, armored scales and their tails are muscular, making them powerful swimmers. Nile crocodiles are prolific hunters, feeding on diverse prey from fish to zebras.
How did the relationship between the plover bird and crocodile develop?
The origins of the mutually beneficial relationship between the plover bird and the crocodile are steeped in scientific theory and ancient legend. There are a few predominant hypotheses about how these two unlikely allies formed their symbiotic bond.
One theory is that prolonged proximity and interactions between the plover and crocodile species over time led to the establishment of a cleaning symbiosis. Plovers feed along muddy shorelines in close contact with crocodiles, making them a readily available cleaning partner. Over generations, crocodiles may have evolved to tolerate plover birds cleaning their mouths and teeth without reacting with aggression or as prey. This allowed the relationship to become entrenched in the species’ behaviors.
Another possibility is that the plover’s cleaning help evolved out of parental instinct. Egyptian plover nests are sometimes located terrifyingly close to basking crocodiles. Yet crocodiles do not disturb the nests. Plover parents may have started removing leeches or food debris from young crocodiles, later expanding that caretaking into cleaning adult crocodiles. This parental care could have established trust between the two species.
Ancient Egyptian legends depict the plover as a caring bird that cries out to crocodiles, telling them to open their jaws so the “toothpick bird” can enter safely and clean their teeth. These folktales indicate the symbiosis was already well established over 3,000 years ago in ancient Egyptian culture.
How does the plover bird clean the crocodile’s teeth?
The plover bird cleans the crocodile’s mouth and teeth using an ingenious technique observed by scientists and locals alike in equatorial Africa.
To initiate cleaning, the plover will typically stand atop the crocodile’s snout and issuing a trilling call while pecking lightly at the plates around the crocodile’s eyes and nostrils. The crocodile responds by gaping its jaws wide open, allowing the bird access.
The plover then turns around and deftly hops inside, walking headfirst down the crocodile’s tongue into the dangerous terrain of its mouth. These fearless birds have been observed to fully enter crocodiles’ mouths and even venture down their throats. However, plovers mainly clean the exposed teeth surfaces.
Once inside, the plover picks and pulls out food debris stuck between the crocodile’s teeth using its slender beak. Its dexterous beak can reach between teeth and into crevices along the gums that are difficult for a crocodile to clean itself. This dental hygiene service provides tangible benefits to the crocodiles’ health.
Amazingly, the crocodile complies peacefully with the plover’s meticulous cleaning, neither attacking the bird nor snapping its jaws shut. This tolerance Indicates the crocodile recognizes the plover’s helpful role.
Why does the crocodile allow the plover bird to clean its teeth?
Scientists have proposed several explanations for why crocodiles tolerate plover birds entering their mouths and cleaning their ferocious teeth:
- The crocodiles benefit by having debris, parasites and food material cleared from their teeth. This may improve dental health and prevent infections or abscesses.
- Plovers may also remove parasites like leeches from inside the crocodile’s mouth that are harder for crocodiles to dislodge themselves.
- The sensation of plovers picking their teeth may be satisfying or pleasurable for crocodiles.
- Crocodiles recognize that plovers pose no threat, and are in fact helping to maintain their health and hygiene.
This tolerance between a predator and prey species is extremely rare in the animal kingdom. Most creatures would flee or attack an apparent threat approaching so closely. Yet crocodiles have learned over eons of interactions that plover birds provide helpful cleaning services worth peacefully enduring.
Do the plover birds receive any benefits or payment?
In return for their dental housekeeping services, the plover birds do seem to receive some reciprocal benefits and protection from the crocodiles:
- Crocodiles do not eat or attack the plover birds while they are cleaning. This is an obvious but invaluable payment.
- Plovers gain access to food morsels stuck in crocodile’s teeth as they clean, providing easy foraging.
- Crocodiles tolerate plovers nesting very close to their territory, affording protection from other predators.
Additionally, recent studies indicate that plovers may gain important antibodies and microbial benefits from frequenting crocodile’s mouths. Analysis found shared bacterial microbiota between Nile crocodiles and Egyptian plovers, suggesting digesting crocodile saliva boosts the bird’s immune system.
So the plover birds do seem to enjoy certain privileges and rewards from the crocodiles in exchange for keeping their toothy mouths clean.
Are there any other examples of interspecies cleaning symbioses?
The partnership between the plover bird and the crocodile is one fascinating example of interspecies cleaning symbiosis. Other notable cleaning symbioses include:
- Cleaner wrasses – These small fish enter the mouths of larger reef fish to eat parasites and dead tissue from their gills or scales.
- Cleaner shrimp – Tiny shrimp groom and clean parasites off of fish like groupers and eels.
- Oxpeckers – These birds perch on African ungulates like rhinos to feast on ticks, flies and blood-sucking parasites.
- Magpie and deer – Magpies have been observed eating parasitic ticks and flies off the backs of deer.
In all these cases, the cleaner animal provides a service by removing debris, parasites or diseased tissue from the host. The host tolerates the cleaner’s presence and actions, in some cases even seeking them out. Interspecies cleaning establishes a mutually beneficial symbiosis between very different organisms.
Are there any other notable symbiotic relationships in nature?
Cleaning symbiosis is just one example of the many incredible symbiotic partnerships that have evolved in the natural world. Here are a few other fascinating symbioses:
- Corals and zooxanthellae – Coral polyps provide the algae zooxanthellae with shelter and nutrients from their waste products. The algae perform photosynthesis producing food for the coral and give corals their vibrant colors.
- Acacia trees and ants – Acacias provide food and shelter in the form of nectar and hollow thorns for colonies of stinging ants. The ants, in turn, defend the tree aggressively from herbivores.
- Clownfish and sea anemones – Clownfish secrete a mucus coating that protects them from the stinging tentacles of sea anemones in which they shelter. Their bright coloration also helps lure prey towards the anemones.
- Plants and mycorrhizae fungi – Fungal networks called mycorrhizae colonize plant roots and help plants absorb water and nutrients more efficiently in exchange for sugars from the plant.
- Honeyguide birds and humans – Honeyguides lead humans to bee nests producing honey. The humans then cracks open the nest, leaving the bird to feast on the larvae and wax.
These partnerships highlight how symbiosis has allowed some of nature’s most unlikely allies to thrive together through teamwork and cooperation.
Are the plover-crocodile cleaning relationships still occurring today?
Remarkably, the ancient interspecies bond between the plover bird and the crocodile still persists to this day throughout sub-Saharan Africa.
Ornithologists continue to observe Egyptian plovers fearlessly cleaning Nile crocodiles in modern times, showing this symbiosis has stood the test of time. Recent documentation includes:
- Plover birds have been filmed entering the mouths of wild Nile crocodiles along the Chobe River in Botswana and fastidiously picking their teeth clean.
- A viral photo from Kenya in 2017 captured a plover bird deep inside the jaws of a massive crocodile, demonstrating the birds still carry out this intrepid cleaning behavior.
- Scientists studying Nile crocodiles in Uganda have sighted plover birds picking at crocodile teeth and entering their mouths without any aggression.
All indications are this unique interspecies relationship has remained intact for millennia and continues to thrive today across Africa. Both participating species appear to have evolved instincts and traits to sustain the symbiosis generation after generation.
The plover bird’s valor and the crocodile’s restraint in allowing fussy dental cleanings exemplify an extraordinary partnership product of co-evolution. Their story underscores how mutually beneficial symbioses can arise between the most unlikely of allies in nature.
Conclusion
The symbiotic relationship between the plover bird and the crocodile is truly remarkable in the animal kingdom. A diminutive bird bravely entering the cavernous jaws of a deadly predator to clean its teeth seems unfathomable. Yet the two species have struck an evolutionary bargain that provides advantages for both participants while defying their expected roles.
This cleaning symbiosis vividly illustrates how novel partnerships can become entrenched between entirely different organisms in ecosystems. While predator and prey are terms that imply conflict and antagonism, the plover and crocodile demonstrate even natural enemies can discover common ground through cooperation. Their story is a surprising yet illuminating example of how symbiosis shapes biological communities in amazing ways.
