Humans always have assumed we’ve cornered the market on intelligence. But because of archerfish and other bright lights in the animal kingdom, that idea is itself evolving.
Archerfish normally make their living in the mangrove forests of Southeast Asia and Australia, where they spit water at ants, beetles and other insects living on the trees’ half-submerged roots. The fish’s high-pressure projectiles knock prey from their perches into the water, and the fish swoops in.
This novel feeding behavior, restricted to only seven species of fish, has attracted the attention of researchers ever since it was first described in 1764.
The jet’s tip and tail unite at the moment of impact, which is critical to the success of the attack, especially as the target distance approaches the limit of the fish’s maximum spitting range of about six feet. The fish accomplishes this feat of timing through deliberate control of its highly-evolved mouthparts, in particular its lips, which act like an adjustable hose that can expand and contract while releasing the water.
So in a way, to hit a target that’s further away, the fish doesn’t spit harder. It spits smarter. But just how smart is an archerfish?
Using the archerfish’s spitting habits as a starting point, one researcher trained some lab fish to spit at an image of one human face with food rewards. Then, on a monitor suspended over the fish tank, she showed them a series of other faces, in pairs, adding in the familiar one.
When the trained fish saw that familiar face, they would spit, to a high degree of accuracy. In a sense, the fish “recognized” the face, which should have been beyond the capacity of its primitive brain.