Although most species of large reptiles in the Sydney region are now
restricted to remnant bushland, the blue-tongued lizard
(Tiliqua scincoides) remains abundant. How has this
large, slow-moving reptile managed to persist in the suburbs? We implanted
radio-transmitters into 17 adult blue-tongued lizards and tracked them for six
months (October 1998 to March 1999). Radio-tracked animals utilised 5–17
suburban backyards, but each lizard spent most of its time in a few
‘core’ areas near 2–7 shelter sites. Males had larger home
ranges than females (mean of 12700 v. 5100 m
2 ) and moved further between shelter sites. Gravid
females (mean home range 1000 m 2 ) were more sedentary.
Lizards used corridors of dense vegetation to move between retreat sites, and
actively avoided crossing roads. In sunny weather, lizards typically basked
close to their overnight shelter for 1–4 h each morning until they
obtained body temperatures of approximately 32°C. They maintained high
body temperatures while moving about in the afternoon.
In combination, the following ecological factors may facilitate persistence of
blue-tongued lizards at our suburban study sites. (i) The most important
subgroup of the population in terms of conservation are gravid females, which
are highly sedentary and, thus, less likely to encounter the dangers of
suburbia. (ii) The more ‘expendable’ males move about much more,
but mostly in times and places that involve minimal risk from humans and their
domestic pets. (iii) Lizards show strong site fidelity, spending up to
70% of their time in ‘safe’ locations; importantly, they
avoid roads. (iv) Blue-tongued lizards readily utilise
‘artificial’ shelter sites and the commensal prey species (e.g.
snails) found in most gardens. (v) These lizards can grow rapidly, mature
early, and produce large litters. Because blue-tongued lizards have a long
life span (over 30 years in captivity), populations of adults may persist for
many years in the absence of recruitment.
