Prey Chemical Discrimination by Tongue Flicking Is Absent in the Texas Homed Lizard, Phrynosoma cornutum

We tested tongue-flicking responses to food chemicals and control stimuli in the Texas Homed Lizard (Phrynosoma cornutum) by presenting chemical stimuli on cotton swabs. No evidence of discrimination between prey chemicals (from the ant Pogonomyrmex rugosus), plant chemicals (romaine lettuce), cologne, and distilled water via the lingual-vomeronasal system was detected despite extremely high statistical power. We conclude that P. cornutum does not use tongue flicking to sample chemicals to permit detection and identification of food. Horned lizards forage by moving between ant colonies, capturing numerous ants at each colony by lingual prehension. Because ants are abundant above ground and mobile, visual search may suffice. Despite the absence of evidence for prey chemical discrimination, the lizards tongue flicked up to 15 times in a 60-sec trial: Because homed lizards do not usually enter crevices likely to contain predators and because they rely on crypsis to avoid detection, they are presumably less likely than lizards such as skinks, lacertids, and geckos to use vomerolfaction to detect predators' chemicals. However, homed lizards tongue flick each other during courtship. Therefore, the primary adaptive use of tongue flicking may be for pheromonal communication.