Its original epithet was Sauromalus obesus; and although that name is no longer officially recognized, it is still very common in the literature and it remains in many standard natural history references for North America. In 1998, Bradford D. Hollingsworth examined variations in Sauromalus and concluded that only five species should be recognized. He regarded S. obesus as conspecific with S. ater, and he used S. ater, which has priority, as the specific name of the combined taxon. No subspecies of S. ater are currently recognized. Based primarily on the extensive use of the name S. obesus, a petition to give that name precedence over that of S. ater was submitted to the ICZN. However this reasoning was dubious and the priority of S. ater was maintained. In 2004, ICZN ruled that the name Sauromalus ater was first described by zoologist Auguste Duméril in 1856 and thus had precedence over the name Sauromalus obesus which was not named until 1858 by Baird.
Males are seasonally and conditionally territorial; an abundance of resources tends to create a hierarchy based on size, with one large male dominating the area's smaller males. Chuckwallas use a combination of colour and physical displays, namely "push ups", head-hobbing, and gaping of the mouth to communicate and defend their territory (see animal communication).
Chuckwallas are diurnal animals and as they are exothermic, spend much of their mornings and winter days basking. These lizards are well adapted to desert conditions; they are active at temperatures of up to 102°F (39°C). Chuckwallas hibernate during cooler months and emerge in February.
Mating occurs from April to July, with 5-16 eggs laid between June and August. The eggs hatch in late September.