The term “Anthropocene” was coined to connote humanity’s recent and indelible impact on the Earth. But it is not only geology and the climate that we have altered; our shuffling of species around the globe has thrown wrenches into many an ecosystem. The invasive species we import have been shown to change rapidly upon entering new territory, but how native species respond to these interlopers has not been as well documented.

In central Florida, there is an endangered bird, the snail kite, that, as its name implies, prefers to dine on apple snails. The size and shape of the kites’ curved bills have adapted to be perfect for plucking the snails out of their shells. These native snails are about an inch in diameter. By around 2009, exotic snails—“considered one of the world’s worst invaders,” according to a new study of this particular predation—had taken over. They are about three times as big as the native snails.

Using a combination of demographic data and genetic analyses of the birds, researchers have found that the new, larger snails have ended up facing larger birds with larger bills. The birds’ body mass increased, and the length of their bills increased—just the change required to cope with the larger prey. Not only did bill size increase, it even increased relative to body size, so even though the birds are larger, they still have more pronounced bills.

And the changes clearly helped. These larger birds with larger bills were more likely to survive their first year of life than their smaller, runtier siblings.

The scientists did not look at the alleles responsible for beak length. Even so, they concluded that it is not pure evolution that yields this change, but rather something called "phenotypic plasticity." That's the ability of a single genetic sequence to produce different outcomes depending on variations in the environment.

Phenotypic plasticity is especially responsive to dietary changes, like the new larger food source the kites encountered here. The scientists drew this conclusion partially because neither bill length nor body mass seemed to change breeding patterns. Still, these phenotypic changes could be harbingers of an evolutionary change in the works.

Conservation strategies often aim to protect the long-lived apex predators that (a) are photogenic and capture human hearts; and (b) are thought to be particularly vulnerable to changes in their environments, since their long lives mean they can’t adapt as rapidly as their surroundings.

But if these predators can rapidly adapt to the presence of invasive prey, as suggested here, we might need to reconsider what, exactly, we are trying to conserve: the old, pre-invasion predators? The new, adapted predators? Some mixture of both? If we find that a species is adapting to invasions, it might be better off without any of our conservation efforts.

Nature Ecology and Evolution, 2017. DOI: 10.1038/s41559-017-0378-1 (About DOIs).