Population ecology of the sleepy lizard, Tiliqua rugosa, at Mt Mary, South Australia

A population of the sleepy lizard, Tiliqua rugosa, near Mt Mary, South Australia, was surveyed by random encounter captures along 42 km of transects over a 10 year period from 1982 to 1991. Population size, estimated by the Jolly-Seber method, was lowest (724 adults) following the 1982/1983 drought, but then increased to a plateau (1500-1600 adults) which was maintained for 5 years. Densities in each 1 km segment of the transects varied from 0.3 to 5.5 lizards per hectare. Adjacent segments of the transects varied more than two-fold in lizard numbers, and those differences were consistent over time. Over all years, an estimated 16% of juveniles survived their first year, 42% of those survived a second year, and 62% of those survived a third year. By the third year some juveniles had reached adult size, although others took more than 5 years to mature. The annual survival of adults of all ages was 80-90%, whereas only 4% of juveniles reached adulthood. Cars killed an average of 3% of the adult population each year, and were a major source of mortality. To sustain stable populations adults must live 20-50 years. This long-lived species has a population structure governed by low recruitment, but long survival of established adults. It differs from the rapid turnover dynamics reported for many other lizard species.