Why do snakes flick their tongues? (Hint: it’s not just about smelling).

By Seriously Science | November 18, 2013 7:00 am
Figure 1 Illustration of the externally visible landmarks which were digitized: the right tip of the tongue, the left tip of the tongue, the point of bifurcation of the fork, the midtongue, and the posteriormost visible point of the tongue.

Figure 1
Illustration of the externally visible landmarks which were digitized: the right tip of the tongue, the left tip of the tongue, the point of bifurcation of the fork, the midtongue, and the posteriormost visible point of the tongue.

It has long been thought that snakes flick their tongues in order to “smell” their environments. However, is this the only reason for the seemingly-constant snake tonguing? To see what else snakes might be up to with all that lingual action, these biologists recorded snake tongues with four high-speed video cameras and reconstructed a 3D model of the tongue in motion. This detailed investigation revealed that the snakes actually perform two types of tongue flick: one for smelling things in the air, and another that seems optimized for tasting objects on the ground. 

The function of oscillatory tongue-flicks in snakes: insights from kinematics of tongue-flicking in the banded water snake (Nerodia fasciata).

“Tongue-flicking is an important sensory behavior unique to squamate reptiles in which chemical stimuli gathered by the tongue are delivered the vomeronasal organ situated in the roof of the mouth. Because tongue-flick numbers can easily be quantified, this behavior has been widely used as a measure of vomeronasal sampling in snakes using related variables such as tongue-flick rate or tongue-flick/attack score. Surprisingly, the behavior itself and especially the function of the oscillatory tongue-flicks remains poorly understood. To describe the overall kinematics of tongue-flicking in the colubrid snake Nerodia fasciata and to test predictions on the function of oscillatory tongue-flicks, we filmed the tongue-flicks of 8 adult Nerodia fasciata using 4 synchronized high-speed cameras. Three-dimensional kinematic and performance variables were extracted from the videos in order to quantify tongue movements. Based on the kinematic analysis, we demonstrate the existence of 2 functional and behavioral tongue-flick categories. Tongue-flicks with oscillations meet all the criteria for being adapted to the collection of odorants; simple downward extensions appear better suited for the rapid pick up of nonvolatile chemical stimuli from the substrate or a food item. External stimuli such as tactile and/or vomeronasal stimulation can induce a shift between these categories.”

Bonus figure from the full text:

Figure 2:Drawings and representative kinematic profiles illustrating the movements of the tongue for the 3 TFTs. [tongue-flick types] (A) Successive tongue movements in an SDE. (B) Successive tongue movements in an SO. (C) Successive tongue movements in MOs. The representative kinematic profiles illustrate the movement of the point of bifurcation (solid line) and the movement of the tongue tips (dashed line) in the sagittal plane for the 3 TFTs.

Figure 2:Drawings and representative kinematic profiles illustrating the movements of the tongue for the 3 TFTs. [tongue-flick types] (A) Successive tongue movements in an SDE. (B) Successive tongue movements in an SO. (C) Successive tongue movements in MOs. The representative kinematic profiles illustrate the movement of the point of bifurcation (solid line) and the movement of the tongue tips (dashed line) in the sagittal plane for the 3 TFTs.

Related content:
NCBI ROFL: The mechanics of slithering locomotion.
NCBI ROFL: Snakes vs. dentist: pick your poison.
NCBI ROFL: Real men prefer curvy cakes and straight snakes.

CATEGORIZED UNDER: fun with animals
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