Study
Why snakes have forked tongues
Schwenk, Kurt
Science, 1994
A synthesis of tongue morphology, vomeronasal anatomy and trail-following behaviour across squamates, testing the competing explanations for why the tongue is forked at all: touch, chemical sampling of two points at once, or an incidental consequence of tongue shape.
- Studied in
- Serpentes, Squamata
- Sample size
- synthesis of comparative anatomy and behaviour
The fork is best explained as simultaneous sampling of two points in space. The tips are held apart by roughly the width of a chemical trail, each tip delivers to its own vomeronasal opening, and animals with forked tongues follow scent trails by comparing the two sides — turning towards whichever tip carries the stronger signal. Forked tongues have evolved repeatedly in lineages that trail-follow and are absent in most that do not.
What it means
The authors' reading, and ours. Where they differ, that difference is the point.
How the authors put it
The forked tongue is an adaptation for tropotaxis — edge-detection in a chemical gradient — rather than for touch or for greater sensitivity.
How NatureHQ reads it
This is the study that makes "snakes smell with their tongues" a half-truth rather than a myth. The tongue does not smell anything; it has no chemosensory cells. It is a sampling device that delivers molecules to an organ in the roof of the mouth, and the fork exists so that two samples arrive at once from slightly different places. That is a stereo comparison, which is a genuinely different and better thing than a nose on a stick — it is how the animal gets a direction rather than a concentration.
- A comparative and functional synthesis rather than a single decisive experiment.
- Trail-following performance with an experimentally unforked tongue is difficult to test without impairing the animal in other ways.
- The correlation between forking and trail-following is strong but not perfect across squamates.
What this study is used for on NatureHQ
One study can inform several subjects. Here is everywhere this one is cited.
Published by: American Association for the Advancement of SciencePublished in Science or Science Advances (AAAS).
doi.org/10.1126/science.263.5153.1573
This reference was resolved automatically against Crossref on 2026-08-11.
NatureHQ summarises research in its own words and does not reproduce published text. Reviewed 2026-08-11.