Mechanism of defensive inflation in the chuckwalla, Sauromalus obesus

The chuckwalla, Sauromalus obesus, avoids predation by wedging itself in a rock crevice and inflating its lungs beyond their normal inspiratory volume. Buccal and pulmonary pressures were recorded in S. obesus during defensive inflation and wedging. Maximum pulmonary pressure generated during defensive wedging was significantly higher and was achieved faster than that of nonwedging inflation. During inflation and wedging, S. obesus forces air into the lungs by pulsatile contraction of the buccal cavity. Buccal pulse pumping is an ancestral ventilation behavior of vertebrates that S. obesus uses for defensive inflation. © Wiley‐Liss, Inc.