It is the largest of the five species of chuckwallas and the most endangered. In the reptile class, desert iguanas, chuckwallas, and the red diamond rattlesnakes can be seen. San Esteban chuckwallas may live for 25 years or more. The two largest lizards in the canyon are gila monsters and chuckwallas. Chuckwallas may live for 25 years or more. Peninsular chuckwallas are stocky, wide-bodied lizards with flattened midsections and prominent bellies. Chuckwallas hibernate during cooler months and emerge in February. Chuckwallas brumate during cooler months and emerge in February. Chuckwallas are stocky, wide-bodied lizards with flattened midsections and prominent bellies.