Does evolution in isolation from mammalian predators have behavioural and chemosensory consequences for New Zealand lizards?

Recently introduced mammalian predators have had devastating consequences for biotas of archipelagos that were isolated from mammals over evolutionary time. However, understanding which antipredator mechanisms are lost through relaxed selection, and how they influence the ability of prey to respond to novel predatory threats, is limited. The varying effects on native lizard populations of the relatively recent and patchy history of mammalian introductions to New Zealand’s islands provide an opportunity to examine the consequences of relaxed selection. We assess behavioural patterns and predator detection abilities of native lizards, using chemicals of native reptilian and introduced rodent predators as cues. Focal lizard populations were isolated from predatory mammals for up to 16 million years; some now co-occur with mammals, while others remain in mammal-free locations. A skink species that evolved with mammals and has recently been introduced to New Zealand is included for comparison. Lizard behavioural patterns were correlated with recent and historical experience of mammals. Lizards always isolated from mammals exhibited the most antipredator freeze behaviour, whereas one that coevolved with mammals exhibited greatest activity (movements). However, predator chemical cues did not induce specific antipredator responses in any species indicating that these behavioural patterns are not linked to chemosensory predator detection alone.