Like many skinks (3), the western spiny-tailed skink is most active during the day (5), basking and foraging within easy reach of its rocky shelters. The diet consists mainly of insects (4), although adults will also eat plant material, and the diet may change seasonally (8). Like many Egernia species, the western spiny-tailed skink has the habit of using specific defecating sites, resulting in small piles of faeces that may mark the group’s territory (4) (5) (7) (9).
The western spiny-tailed skink shows an unusual level of social complexity, living in stable, extended family groups of up to 17 individuals, consisting of breeding partners, offspring, and related adults (5) (9) (10). Group members appear to use chemical cues to recognise each other (5) (11) (12), and bask close together, as well as sharing shelters (9). Living in such a group may improve vigilance against predators, or allow offspring access to otherwise potentially limited food and refuges (5) (10) (13). Also unusually for a lizard, the western spiny-tailed skink is monogamous, with breeding pairs remaining together over many seasons (5) (14). The female gives birth to up to eight live young between February and March, after a gestation period estimated at three to four months (15). The newborn skinks average a snout-vent length of 6.7 centimetres (15), and take over five years to reach maturity, after which they may disperse to nearby groups (5) (9) (10). The lifespan of this species may be up to 25 years (5) (15).