Extreme tolerance for nocturnal emergence at low body temperatures in a high-latitude lizard: implications for future climate warming

Abstract

High-latitude lizards live in environments where ambient air temperature at night is frequently below retreat temperatures, which likely has implications for nocturnal emergence and activity. However, patterns of lizard activity at night under current temperate climates are poorly understood, a situation that limits our understanding of potential effects of climate change. We investigated patterns of nocturnal emergence and activity in the cold-adapted, viviparous gecko (Woodworthia 'Otago/Southland'). We measured operative environmental temperature (Te) available to geckos that emerged at night and simultaneously assessed nighttime emergence activity using time-lapse trail cameras. Also, we assessed field body temperature (Tb) of emerged geckos of various life history groups at night using thermography to understand how current weather conditions affect field Tb of emerged geckos. Our results show that Te, nocturnal emergence activity and field-active Tb increased with nighttime air temperature. Nocturnal emergence was highest in spring and summer but also occurred in autumn and (unexpectedly) in winter. Geckos were active over a broad range of Tb down to 1.4°C (a new record low for lizards) and on rock surfaces typically warmer than air temperature or Tb. We conclude that this nocturnal, high-latitude lizard from the temperate zone is capable of activity at low winter temperatures, but that current climate limits emergence and activity at least in autumn and winter. Activity levels for cool-temperate reptiles will probably increase initially as climates warm, but the consequences of increased nocturnal activity under climate change will probably depend on how climate change affects predator populations as well as the focal species' biology.