Population responses of common lizards inside a predator-free dryland sanctuary

Predator-free sanctuaries can assist the conservation of multiple endemic species, but quantitative evidence of these benefits is often lacking, especially for herpetofauna. We measured population responses of three common lizard species (schist geckos, Woodworthia ‘Central Otago’; McCann’s skinks, Oligosoma maccanni; and southern grass skinks, O. aff. polychroma Clade 5) 1 year before and 5 years after mammalian predators were removed inside a mammal-proof fence in a dry grass/shrubland habitat with abundant schist rock in Central Otago, New Zealand. Gecko counts in 25 artificial retreats (ARs) along replicated, 250-m long transects inside the fence increased from 5.2 to 17.7 per transect, compared with 3.3 to 5.4 per transect outside the fence where predators were present. This indicates a doubling of counts inside the fence when changes outside the fence are accounted for. The number of skinks seen along these transects increased from 1.3 to 2.3 per transect without predators, compared with 0.6 to 0.4 with predators. Lizard tracking tunnel indices (recorded only after predators were removed) were significantly higher without predators (62% geckos, 42% skinks) than where predators were present (12% geckos, 2% skinks). Tail loss in geckos was significantly higher where predators were present (24%) than where they were absent (1%). These data suggest that common lizard species are being suppressed to a significant degree by mammalian predators and demonstrate the potential for their recovery where predators are removed.