Everglades Alligators Keep Birds Safe (and Eat Their Chicks)
In the Everglades, birds and alligators form an unlikely but beneficial partnership. Several types of water birds, including herons and egrets, choose to nest directly above the territory of alligators, using the alligators almost like bodyguards. The alligators’ presence protects their chicks from predators such as raccoons or opossums. In exchange, the alligators snack on the chicks that have the misfortune to fall out of their nest.
In a new study in the journal PLOS One, a group of Florida-based researchers compared how alligators living under these bird colonies fare in contrast to those who don’t live near bird nests. The goal: to see if the arrangement is as advantageous to the 'gators as to the birds. They studied almost 40 different female, adult alligators living in similar habitats in the Everglades. Some lived near nesting bird colonies belonging to egrets, herons, and similar birds, while some lived in habitats without any signs of these nests.
Alligators that lived near nesting birds were in much better physical condition (as measured by blood samples, body mass, and body length) than alligators who didn’t have any bird neighbors, they found. The researchers hypothesize that the alligators living near nesting colonies must be better fed from preying on ejected chicks, contributing to their significantly better physical conditions.
“Our study is the first to demonstrate a mutually beneficial relationship between nesting birds and a crocodilian,” study co-author Lucas Nell explains in a press statement. “Crocodilians and nesting birds co-occur throughout the tropics, so these may be globally important ecological associations.”
For birds in danger of having their nests raided, “enemy-free space can be gained by nesting near more formidable animals for physical protection,” the researchers write. Think of it as “the enemy of my enemy is my friend” theory. While an alligator wouldn’t climb up a tree to steal chicks from a nest, a raccoon would. So hanging around an alligator can prove advantageous even though it, too, is a potentially dangerous predator. In turn, the alligators benefit from eating the chicks that wouldn’t survive anyway—those that are bumped out of the nest when a bird lays more eggs than it’s capable of taking care of.