Alligators aren't always the deadly predators you'd expect. Sometimes, they act as bodyguards for birds - for a price. Scientists have found that breeding birds that nest above alligators for protection from mammalian predators may also provide a source of food for the alligators living in the Everglades.
For many bird species, nest predation is the greatest threat to raising chicks. Long-legged wading birds, like herons, egrets, ibises, storks and spoonbills may choose nesting sites above resident American alligators. Most likely, these birds take advantage of protection from nest predators such as raccoons and opossums. But while these protections are well-documented, scientists have long wondered what benefit there was for the alligator.
In this latest study, the researchers compared the body condition of about 40 female alligators living with and without wading bird nesting colonies in similar habitat in the Everglades. In order to measure body condition, the scientists took blood samples and measured the mass and length of the alligators.
In the end, the researchers found that the body condition of alligators found near wading bird nesting colonies was higher than those in similar habitat without active colonies, independent of a range of environmental variables. The mean body condition based on size and shape for colony-associated alligators captured for the study ranked as the 63rd percentile, while that for non-colony females ranked as the 17th.
So what does this all mean? It appears as if there's a beneficial interaction between alligators and nesting birds. It could be that while birds receive the benefits of some protection, chicks that fall from the nest could provide a food source for the alligators. In other words, the birds are paying for the protection that they receive from the alligators.
"Our study is the first to demonstrate a mutually beneficial relationship between nesting birds and a crocodilian: nesting wading birds provide nutrition for alligators that, by their mere presence, create predator-free space for birds," said Lucas Nell from the University of Florida, one of the researchers. "Crocodilians and nesting birds co-occur throughout the tropics, so these may be globally important ecological associations."
The findings reveal a bit more about how birds and crocodilians provide a mutually beneficial relationship to one another. While the alligators help guard the nest, they also prey on any chicks that fall from the nest, using them as payment for services rendered.
