Weirdest of friends: the mutually beneficial relationship between alligators and wading birds

An alligator tries to eat a raccoon at a bait station in southwest Florida. Photo Credit: Florida Fish and Wildlife Conservation Commission.

A recent study published in PLOS One found that alligators benefit when wading birds nest in their territory. Benefits to birds from this relationship are clear and well-documented--nesting near alligators keeps away many of the predators that might otherwise threaten eggs or chicks, like raccoons and opossums, increasing nesting success. This research shows that the relationship is actually an example of "mutualism"--that is, a relationship between species that is good for both of them--rather than "commensalism" (a relationship that is good for one species, while not really helping or hurting the other). Alligators that live near nesting wading bird colonies were generally in better physical condition than other similar alligators that didn't live near birds (63rd percentile for body weight versus 17th percentile). This difference is mainly explained by alligators getting the chance to feed on "dropped" chicks--hatchlings that are ejected from the nest when a bird has too many young to successfully feed and raise.

One of the things we love about this study is how effectively it illustrates that ecological relationships aren't always simple or obvious (because PLOS One is open access, you can read the whole study for free here). Based on what we know now, we'd expect a drop in the bird population to negatively effect the health and fitness of some alligators, or a decline in alligator populations to lead to lower reproductive success for wading birds. But that isn't obvious without looking more closely at how these species interact. It's an important reminder of how amazing and subtly interconnected ecological systems are.