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. 2023 Feb 14;18(2):e0281285. doi: 10.1371/journal.pone.0281285

Table 1. Nine behaviors recorded for snakes included in the study.

Behavior Description
Directional movement The distance (cm), direction (toward, away, or orthogonal of the sound), and length of time (sec) in which the snake moves. Measured at the head. Body movement independent of head noted but not measured directly.
Cautionary exploratory movement The first 1/3rd of body moves in multiple directions while the rest of body is stationary.
Tongue flicks The number of times the tongue goes in and out of the mouth. One motion of the tongue in and out = 1.
‘Freeze’ response While snake is alert (head elevated and body tense), a sudden stop of body movement, not in relaxed posture.
Head jerks Rapid lateral movements of the head independent body movement.
Hisses Rapid exhalation of air through the mouth to make a hissing noise.
Dropping lower jaw A distinctive drop of the lower jaw for a period, which exposes the fangs in a defensive manner.
Periscoping Vertical movement of the head (and sometimes part of body) upwards with a 45º angle or greater, not in an s-curve position.
Fixation Head facing same direction while body moves laterally.