The forked tongue of snakes allows them to track down prey or a mate by following an aromatic trail that might not even be detected by other animals, a researcher reports.
Kurt Schwenk, a biologist at the University of Connecticut, said snakes have the ability to absorb scent molecules with their split tongue tips and then place those molecules on special oral sensors that help the reptiles interpret what they smell.It is a highly developed sensing system that may be key to the long success of snakes as a species, Schwenk says Friday in a study published in the journal Science. The forked tongue, he said, helps make the snake one of the keenest trackers in nature.
"The ability to follow that trail to a meal or to a mate is of fundamental importance," said Schwenk. "Though it is kind of a sense of smell, it is not the kind of smeller that we have. We can't even relate to what it is they are sensing."
Schwenk said nearly all snakes have deeply forked tongues, and he believes this makes them much better trackers than other animals, such as lizards, that have more modestly forked tongues.
As a result, he said, snakes have a better ability to detect, stalk and capture prey and have "a terrific evolutionary advantage."
When following a trail, a snake frequently flicks its tongue, testing the air and also touching the ground. Schwenk said high-speed photos show that during each flick, the snake separates the tips of its tongue so that the ends are splayed apart as far as possible.
In this way, the snake can test the chemical strength of the scent trail at two different points and, thus, determine the direction the trail is heading. If the left side of the tongue detects a weaker scent than the right, then the snake knows to slither slightly right to stay in the center of the trail.
The split tongue, in effect, gives a stereo sense to the trail in a manner similar to the way that two ears can give a direction for the source of a sound.
"This sense is clearly very, very keen in a way that we can hardly comprehend," said Schwenk.
Rattlesnakes, he said, can even determine if a mouse has been bitten or not.
A hunting rattlesnake will ambush a mouse with its fangs, injecting venom, and then allow the rodent to run away and die, said Schwenk. This leaves the snake with the problem of deciding which trail to follow - the one left by the healthy mouse approaching or by the bitten mouse retreating.
"It has been demonstrated that a rattlesnake can tell the difference," said the researcher. "This is an ability unique to rattlesnakes."