Birds use alligators as guard dogs to protect their nests from mammals

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When it comes to avoiding predators in the swamps, long-legged wading birds get by with a little help from their toothy reptilian friends. In an effort to keep their eggs beyond the appetites of mammals such as possoms, many bird species build their nests above where alligators dwell. But this relationship isn't as one-sided as it seems - it works in the alligator's favour as well.

For many birds, losing their eggs to predators is the biggest threat to their next generation. Nesting above a predator such as an alligator is a gamble. While there is a chance they may become an easy meal for the alligators, the reptiles chase off or eat other predators which may have their eyes on the bird's eggs.

Scientists from the University of Florida studied alligators in the Everglades to see if there was any difference in the condition of animals that lived underneath nesting birds compared with those didn't. Two families of birds tend to nest over the reptiles, the Pelecaniformes, such as the white ibis and great egret, and the Ciconiiformes, which include birds such as herons.

Taking to the Everglades at night, the researchers snared adult and juvenile alligators - at 125 cm (4 ft) and above in length - at a number of locations after nesting had finished, to avoid disturbing the birds. The bird species were mainly egrets and herons.

They found that reptiles with birds nesting nearby were in much better physical shape compared to those without a nest overhead. On average, those alligators found near to wading birds were heavier, with more energy reserves than those not living near a nest. What's more, this effect was independent of other environmental factors, demonstrating a close relationship between the birds and the reptiles.

It is believed that when the birds nest a few metres above, out of reach of the snapping jaws, they get the protective benefits. The alligators meanwhile, get the easiest meal in the swamp – making short work of any chicks which fall from the nest. Dr Lucas Nell, a researcher at the University of Florida, told MailOnline: 'Our study provides solid evidence that both nesting birds and alligators benefit from one another during critical life stages: nesting and chick-rearing for birds, and pre-egglaying for alligators.