This species frequently inhabits cliff-bound islands. On larger, northern islands, vegetation is dominated by Pohutukawa (Metrosideros excelsa), Mahoe (Melicytus ramiflorus), Karo (Pittosporum crassifolium) and Kanuka (Kunzea ericoides) (Cree 2014). The forests on larger, Cook Strait islands are dominated by Kohekohe (Dysoxylum spectabile), mahoe, Ngaio (Muoporum laetum), Taupata (Coprosma repens) and Akiraho (Olearia paniculata). The vegetation on smaller and less modified islands consist of low, wind-shorn plants such as Taupata. This species has also been found among flax bushes (Harakeke, Phormium tenax), and sheep pasture on Stephens Island (Takapourewa). It frequently inhabits seabird burrows on offshore islands (Cree 2014). Densities of Tuatara in remnant and regrown coastal forest on Stephens Island can reach 2,015 ind / ha, five times the density in paddocks on the island and 20 times that known from any other island (Carmichael et al. 1989, Cree and Butler 1993). This is an extremely long-lived species, with a maximum recorded lifespan of 91 years, and adult females reproduce once every four years on average (Moore et al. 2007). The species' true longevity and generation length are, however, unclear as the longest-studied individuals are still alive (R. Hitchmough pers. comm. 2019).

This species has was once widespread on the New Zealand mainland based on subfossil remains, but was lost at some point in the 800 years following human arrival (Hay et al. 2010). It has been suggested that it may have survived on the mainland until about the 1700s. It has since (within the last 100 years) been lost from 10 offshore islands on which it previously occurred. It has been reintroduced to the mainland in a small number of fenced sanctuaries (R. Hitchmough pers. comm. 2019).  This species remains naturally present on approximately 32 offshore islands, extending from the Poor Knights Islands (35º28'S), northeast of the North Island of New Zealand, to North Brother Island (41°07'S) in the Cook Strait (van Winkel et al. 2018). The largest subpopulation (estimated by Moore et al. 2007 to represent half the extant population of this species at the time) is found on Stephens Island, which has an area of 150 ha. This species has been reintroduced to seven islands within the Cook Strait, and one in the Bay of Plenty following local extinction. It occurs at altitudes ranging from just above high tide level to 722 m asl (Department of Conservation 2001, Cree 2014; R. Hitchmough pers. comm. 2019).

Action recovery plans for this species have been in place sine 1993 (Cree 2014). The most recent action recovery plan established in 2001 recommends maintaining the security of island populations, as well as improving and maintaining rodent eradication of island populations. Continuing captive management programmes to increase the productivity of wild populations on islands where they currently occur, as well as islands/regions where they previously occurred, as well as to safeguard against disasters impacting wild populations (Department of Conservation 2001). Moore et al. (2007) found that a long-term decline in body condition could only be distinguished from short-term fluctuations with long-term monitoring (in excess of 22 years in this species), highlighting the importance of long-term population monitoring of this species.

Between 1995 and 2011, this species has been translocated to seven islands where they are known, or assumed with a high level of confidence to have once occurred. On mainland New Zealand, this species has been released into fenced, outdoor habitats that exclude mammalian predators (Cree 2014).

This species is listed on CITES Appendix I.