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 inspirat ory volume. Buccal and pulmonary pressures were recorded in S. obesus during defensive inflation and wedging. Maximum pulmonary pressure gen erated during defensive wedging was significantly higher and was achie ved faster than that of nonwedging inflation. During inflation and wed ging, S. obesus forces air into the lungs by pulsatile contraction of the buccal cavity. Buccal pulse pumping is an ancestral ventilation be havior of vertebrates that S. obesus uses for defensive inflation. (C) 1994 Wiley-Liss, Inc.