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Visually guided avoidance in the chameleon (Chamaeleo chameleon): response patterns and lateralization.

Lustig A, Ketter-Katz H, Katzir G - PLoS ONE (2012)

Bottom Line: We found two equal-sized sub-groups, each displaying lateralization of motor responses to a given direction of stimulus approach.Such an anti-symmetrical distribution of lateralization in a population may be indicative of situations in which organisms are regularly exposed to crucial stimuli from all spatial directions.This is because a bimodal distribution of responses to threat in a natural population will reduce the spatial advantage of predators.

View Article: PubMed Central - PubMed

Affiliation: Department of Neurobiology and Ethology, University of Haifa, Haifa, Israel. Lustigavi@gmail.com

ABSTRACT
The common chameleon, Chamaeleo chameleon, is an arboreal lizard with highly independent, large-amplitude eye movements. In response to a moving threat, a chameleon on a perch responds with distinct avoidance movements that are expressed in its continuous positioning on the side of the perch distal to the threat. We analyzed body-exposure patterns during threat avoidance for evidence of lateralization, that is, asymmetry at the functional/behavioral levels. Chameleons were exposed to a threat approaching horizontally from the left or right, as they held onto a vertical pole that was either wider or narrower than the width of their head, providing, respectively, monocular or binocular viewing of the threat. We found two equal-sized sub-groups, each displaying lateralization of motor responses to a given direction of stimulus approach. Such an anti-symmetrical distribution of lateralization in a population may be indicative of situations in which organisms are regularly exposed to crucial stimuli from all spatial directions. This is because a bimodal distribution of responses to threat in a natural population will reduce the spatial advantage of predators.

Show MeSH
Head angles relative to the moving threat.Provided are the head angles relative to a moving threat under angular velocities of 15°/s, 35°/s and 70°/s. Each data point (mean ± SE) is from six readings (three per chameleon).
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pone-0037875-g005: Head angles relative to the moving threat.Provided are the head angles relative to a moving threat under angular velocities of 15°/s, 35°/s and 70°/s. Each data point (mean ± SE) is from six readings (three per chameleon).

Mentions: (a) Rotation of the chameleon on the pole within the opaque-white sphere elicited no apparent change of position: the chameleon maintained its position on the pole and rotated with it, clockwise or anti-clockwise [see Video S1]. (b) When perched on a stationary pole and exposed to a threat moving in an arc, the chameleons responded in highly synchronized adjustments of their position relative to the threat (Fig. 5). The analysis showed that both α and β were maintained highly stable in all tests and under all three angular velocities. The angular velocity of 15°/s was the velocity used in the main experiment, as well as in control experiment (a). The results of both control experiments thus demonstrated that the avoidance response of the chameleons is related to the motion of the visual threat and is not elicited by inertia.


Visually guided avoidance in the chameleon (Chamaeleo chameleon): response patterns and lateralization.

Lustig A, Ketter-Katz H, Katzir G - PLoS ONE (2012)

Head angles relative to the moving threat.Provided are the head angles relative to a moving threat under angular velocities of 15°/s, 35°/s and 70°/s. Each data point (mean ± SE) is from six readings (three per chameleon).
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC3369868&req=5

pone-0037875-g005: Head angles relative to the moving threat.Provided are the head angles relative to a moving threat under angular velocities of 15°/s, 35°/s and 70°/s. Each data point (mean ± SE) is from six readings (three per chameleon).
Mentions: (a) Rotation of the chameleon on the pole within the opaque-white sphere elicited no apparent change of position: the chameleon maintained its position on the pole and rotated with it, clockwise or anti-clockwise [see Video S1]. (b) When perched on a stationary pole and exposed to a threat moving in an arc, the chameleons responded in highly synchronized adjustments of their position relative to the threat (Fig. 5). The analysis showed that both α and β were maintained highly stable in all tests and under all three angular velocities. The angular velocity of 15°/s was the velocity used in the main experiment, as well as in control experiment (a). The results of both control experiments thus demonstrated that the avoidance response of the chameleons is related to the motion of the visual threat and is not elicited by inertia.

Bottom Line: We found two equal-sized sub-groups, each displaying lateralization of motor responses to a given direction of stimulus approach.Such an anti-symmetrical distribution of lateralization in a population may be indicative of situations in which organisms are regularly exposed to crucial stimuli from all spatial directions.This is because a bimodal distribution of responses to threat in a natural population will reduce the spatial advantage of predators.

View Article: PubMed Central - PubMed

Affiliation: Department of Neurobiology and Ethology, University of Haifa, Haifa, Israel. Lustigavi@gmail.com

ABSTRACT
The common chameleon, Chamaeleo chameleon, is an arboreal lizard with highly independent, large-amplitude eye movements. In response to a moving threat, a chameleon on a perch responds with distinct avoidance movements that are expressed in its continuous positioning on the side of the perch distal to the threat. We analyzed body-exposure patterns during threat avoidance for evidence of lateralization, that is, asymmetry at the functional/behavioral levels. Chameleons were exposed to a threat approaching horizontally from the left or right, as they held onto a vertical pole that was either wider or narrower than the width of their head, providing, respectively, monocular or binocular viewing of the threat. We found two equal-sized sub-groups, each displaying lateralization of motor responses to a given direction of stimulus approach. Such an anti-symmetrical distribution of lateralization in a population may be indicative of situations in which organisms are regularly exposed to crucial stimuli from all spatial directions. This is because a bimodal distribution of responses to threat in a natural population will reduce the spatial advantage of predators.

Show MeSH