THE MECHANICS OF OVOPHAGY IN THE BEADED LIZARD (HELODERMA-HORRIDUM)

The beaded lizard (Heloderma horridum) is a large diurnal predator tha t feeds predominantly on juveniles in vertebrate nests and eggs Bird e ggs constitute a special problem for predators as the energetic conten t is shielded by a hard calcareous shell. Still, eggs of ground nestin g birds such as quail constitute a large part of the diet of Heloderma horridum. We investigated the mechanics of the egg eating behavior in H. horridum. We examined the morphology of the feeding system, measur ed egg toughness, and calculated bite forces of H. horridum. Additiona lly, we videotaped feeding sequences and simultaneously recorded the a ctivity patterns of the jaw muscles. Egg eating behavior consists of a fixed behaviorial pattern including five distinct stages: approach, p iercing, uptake, crushing, and swallowing. Two of these (piercing and crushing) can be directly related to the egg eating behavior in H. hor ridum. The piercing stage consists of several bites during which the a nterior teeth are used to puncture (but not crush) the egg. Next, duri ng the crushing stage the egg is crushed within the oral cavity (no lo nger any tooth contact). Based on our results, we conclude that behavi orial adaptations and subtle modifications of the motor patterns durin g feeding are present in H. horridum which allow the lizard to be an e fficient ovophageous predator.