Some Like It Hot: Camera Traps Unravel the Effects of Weather Conditions and Predator Presence on the Activity Levels of Two Lizards

Abstract

It is generally assumed that favourable weather conditions determine the activity levels of lizards, because of their temperature-dependent behavioural performance. Inactivity, however, might have a selective advantage over activity, as it could increase survival by reducing exposure to predators. Consequently, the effects of weather conditions on the activity patterns of lizards should be strongly influenced by the presence of predators. Using remote camera traps, we test the hypothesis that predator presence and weather conditions interact to modulate daily activity levels in two sedentary cordylid lizards, Karusasaurus polyzonus and Ouroborus cataphractus. While both species are closely related and have a fully overlapping distribution, the former is a fast-moving lightly armoured lizard, whereas the latter is a slow-moving heavily armoured lizard. The significant interspecific difference in antipredator morphology and consequently differential vulnerability to aerial and terrestrial predators, allowed us to unravel the effects of predation risk and weather conditions on activity levels. Our results demonstrate that K. polyzonus is predominantly active during summer, when ambient temperatures are favourable enough to permit activity. In contrast, a peak in activity during spring was observed in O. cataphractus, with individuals being inactive during most of summer. While favourable weather conditions had a strong effect on the activity levels of K. polyzonus, no such relationship was present in O. cataphractus. Contrary to our hypothesis, the presence of terrestrial predators does not seem to affect daily activity levels or alter the influence of weather conditions on activity levels. We conclude that inactivity in O. cataphractus appears to be related to seasonal differences in vulnerability to predators, rather than the presence of predators, and highlight the importance of additional selective pressures, such as food abundance, in determining the species’ activity levels.

Proximate causes of variation in dermal armour: insights from armadillo lizards

“…water balance regulation). In contrast, although mongoose predation has played a key role in the evolution of armour in armadillo lizards Mouton 2015, Broeckhoven et al 2015), differences in predation risk or pressure among study locations do not appear to have a major influence on variation in dermal armour. Rigorous phylogenetic comparative analyses should, however, be conducted to investigate whether this trend can be extrapolated to the diversification of body armour in general, particularly that of dermal armour.…”

“…G. pulverulenta) or group of individuals (e.g. S. suricatta) present at a specific locality (Broeckhoven and Mouton 2015). Nevertheless, differential exposure to predators, rather than predator species or densities, might have contributed, albeit weakly, to variation in body armour.…”

Enemy at the gates: Rapid defensive trait diversification in an adaptive radiation of lizards

“…Here, an increase in body armor would have been favored to avoid extraction from the crevice by terrestrial predators, such as mongooses and snakes (Cooper et al. ; Broeckhoven and Mouton ). Further support is provided by the fact that species that differ in antipredator phenotype occur sympatrically, suggesting that ecological interactions, besides competition for food or microhabitat, might have influenced diversification.…”

“…Further support is provided by the fact that species that differ in antipredator phenotype occur sympatrically, suggesting that ecological interactions, besides competition for food or microhabitat, might have influenced diversification. Broeckhoven and Mouton () provide such an example of temporal thermal resource partitioning between O. cataphractus and Karusasaurus polyzonus .…”

Beauty is more than skin deep: a non‐invasive protocol for in vivo anatomical study using micro‐CT

“…After the scanning procedure, the activity of lizards was carefully monitored for 30 days in the laboratory prior to release. In addition, we implemented a post‐release monitoring period of 90 days by means of remote camera trapping (see Broeckhoven & Mouton for a full description of the set‐up). No noticeable side effects of irradiation were observed in the laboratory and the majority of subjects were recovered in the field at the end of the camera trapping period.…”