Monday, October 24, 2011

Hiding In Plain Sight

Phrynosoma modestum is a small (3.7-7.1 cm)
lizard that is found from New Mexico Colorado and 
Oklahoma to San Luis Post, Mexico. JCM

Hiding in plain sight is a well used slogan and many squamates use this principle - to reduced their exposure to predators. Eucrypsis is the name for the type of crypsis used by species to allow them to blend with the environmental background. It may be looking like a leaf, a piece of bark, or a rock. It may also involve behavior, swaying with the branch, moving with a current of water, or freezing in place. Cooper and Sherbrooke (in press) have a forth comming article that describes how the round-tailed horned lizard (Phrynosoma modestum ) mimics rocks, the lizard's body resembles a small stone when it pulls its legs close to its body while simultaneously elevating its back. The authors investigate the efectiveness of the camouflage in  modestum and its dependence on stones by placing a lizards in one of two microhabitats (1) a uniform sand, or (2) sand with surfaceof  rocks about the same size as lizards. Observers who knew which microhabitat contained the lizard was asked to visually locate the lizard. The time to detection was longer and probability of no detection within 60 seconds was higher for lizards on rocky background than on bare sand. In other experiments, lizards were given a choice of sitting on rocky sand or bare sand, a high proportion selected the rocky background throughout the day, but at night all lizards slept among stones. The unique stone mimicing posture gives P. modestum the rounded appearance similar to many naturally eroded stones. Lizards adopted the unusualy posture, but none did so in response to a nearby experimenter, the stimuli that elicits the posture remain unknown.

Citation
Cooper, W. E. and W. C. Sherbrooke. In press.Choosing between a rock and a hard place: Camouflage in the round-tailed horned lizard Phrynosoma modestum. Current Zoology 58(1)

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