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Canid Elicitation of Blood-Squirting in a Horned Lizard (Phrynosoma cornutum)
George A. Middendorf, III and Wade C. Sherbrooke
Vol. 1992, No. 2 (May 1, 1992), pp. 519-527
Stable URL: http://www.jstor.org/stable/1446212
Page Count: 9
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In staged, predator-prey encounters between Texas horned lizards, Phrynosoma cornutum, and a canid, Canis familiaris, 47 of 55 lizards (85%) squirted blood from orbital sinuses. The probability of blood-squirting was not significantly affected by either (1) lizard body temperature (low, 85% vs high, 100%) or (2) time of day (diurnal, 70% vs nocturnal, 70%). A canid was more likely to elicit blood-squirting (100%) than a canid-mimicking human (20%). When the canid was restrained from direct contact, blood-squirting did not occur, but when lizards were simultaneously subjected to human tactile stimulation, 20% squirted blood. Lizards responded similarly to canid saliva and distilled water, implying that saliva does not provide cues used in the discrimination of canids. Overall, tactile cues appear to play a significant role in the elicitation of blood-squirting. Because roadrunners and grasshopper mice are known to not elicit blood-squirting in predator-prey encounters, these data support the canid antipredator defense hypothesis as an explanation of this unique behavior. Blood-squirting appears to be a context-dependent reptilian antipredator display in which elicitation of the squirting response is determined by predator type.