Gators Are a Baby Waterbird鈥檚 Best and Worst Chance of Survival鈥擧ere’s Why
A new study on alligators and nesting waterbirds in the Everglades proves that predator-prey relationships are more complicated than we think.
Hunting isn鈥檛 always about the thrill of the chase. In the Everglades, alligators have adopted a more laid-back strategy: sitting and waiting for dinner to drop out of the sky.
While it may seem contrary to the very definition of 鈥減redator,鈥 a study published earlier this month in found that American alligators are healthier when they hang out under the nests of birds such as Roseate Spoonbills and Little Blue Herons. 鈥淢ost every single breeding female alligator in the Everglades could be sustained during the four-month dry season by dropped chicks alone,鈥 lead researcher and University of Florida graduate student Lucas Nell .
It鈥檚 common for swamp-dwelling birds to nest above alligator-infested waters: The territory keeps animals like possums and raccoons from clambering up into nests and stealing eggs. The defensive ploy is one that birds . The European Fieldfare, for example, nests near Merlins, which are territorial falcons; Black-chinned Hummingbirds do the same with accipiter hawks. This is the first known case, however, where both predator and prey benefit.
For decades, ecologists have focused most of their attention on the negative relationships between birds and gators, says study coauthor Peter Frederick, a University of Florida ecology professor. 鈥淲e鈥檝e discovered that positive forces can be pretty forceful as well,鈥 he says.
Typically, waterbirds produce more offspring than they鈥檙e able to feed and end up with one or two runts that won鈥檛 make it. These weaker chicks eventually get bumped into the swamp below. The fuzzy meals are small, but they鈥檝e become essential to the gator population鈥攅specially in the Everglades鈥 dry season, when most birds are nesting and other food sources like snakes, turtles, and lizards become tricky to reach.
Detangling this symbiotic relationship wasn鈥檛 easy. The team used nooses and even their bare hands to catch (and release within an hour) 39 full-grown female alligators throughout the summers of 2013 and 2014. They drew blood samples and compared the body size of individuals living in parts of the Everglades surrounded by nesting birds to those from other areas.
The results showed that the female gators, which tend to stay in one place while feeding, were fatter when they lived below nesting birds. While most of those calories likely came from tumbling chicks, birds aren鈥檛 the only things dropping from nests. 鈥淚t鈥檚 possible that [alligators] are getting some indirect benefit from the birds鈥 feces as well,鈥 Frederick says. Bird poop may provide extra nutrients to the swamp, leading to more fish for the reptiles to eat.
Of course, not all of the Everglades gators have lost their spirited, predatory ways: The 11-foot beasts will sometimes to coax live chicks straight out of the nest. It's the alligator version of apple picking鈥攋ust way deadlier.