You know how they say it’s a dog-eat-dog world out there? The brown tree snake pictured would like it to be a snake-eat-bird world, but dang it, the bird is just too big. But that didn’t stop the snake from trying.
In fact, a research study published this summer found that brown tree snakes kill oversized birds frequently, even though the snakes can’t actually consume the birds they’ve successfully killed. It’s a classic case of having eyes bigger than your stomach—or, in this case, eyes bigger than your jaw can physically open.
The research suggests brown tree snakes (Boiga irregularishave) have gumption. They’re formidable predators in Guam that have driven some bird species on the island extinct. What’s more, these snakes are going after birds that are too big for them to physically swallow. While we might admire this bravado, there are a couple of problems with this scenario.
For one thing, brown tree snakes are an invasive species on Guam. They’re not supposed to be there. Since they are there, though, they compete with native species for food and other resources. Unchecked, invasive species can wreak havoc on an ecosystem, often because they don’t have natural predators.
A more-specific problem with brown tree snakes in Guam is that the small ones keep killing birds that are too large for them to swallow. That’s not really how the food chain is supposed to work.
“Our study indicates that B. irregularis routinely predate prey that are too large for them to successfully ingest, which causes mortality to the prey but poses little risk to the predator,” the researchers say. “[. . .] Instances of predation that do not result in consumption may have considerable impacts on prey populations.”
In fact, the researchers discovered that brown tree snakes only successfully ingested 52% of the birds they killed. Talk about biting off more than you can chew.