Never smile at a crocodile: Gaping behaviour in the Nile crocodile at Ndumo Game Reserve, South Africa

Price, Cormac; Ezat, Mohamed A.; Hanzen, Céline; Downs, Colleen T.

doi:10.1016/j.beproc.2022.104772

Cited by 3 publications

(1 citation statement)

References 21 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Thermoregulation may be especially important in tropical systems, where aquatic reptiles may emerge at night to cool down if the water is too warm (Nordberg & McKnight, 2020; Thorbjarnarson, 1989). Indeed, mouth gaping, a behaviour that is generally thought to be primarily thermoregulatory (Heatwole et al, 1973), but may also have additional functions, has been observed in several crocodilians at night (Carl et al, 2020; Loveridge, 1984; Price et al, 2022).…”

Section: Introductionmentioning

confidence: 99%

Seasonal, environmental and anthropogenic influences on nocturnal basking in turtles and crocodiles from North‐Eastern Australia

Nordberg

McKnight

2023

Austral Ecology

View full text Add to dashboard Cite

Many ectotherms bask in the sun as a behavioural mechanism to increase body temperature and facilitate metabolism, digestion or gamete production, among other functions. Such behaviours are common during the day, but some nocturnal species are also known to thermoregulate at night, in the absence of solar radiation, through shifts in body posture or microhabitat selection. Additionally, recent work has documented nocturnal basking in freshwater turtles in tropical Australia, though the purpose of the behaviour remains unknown. Here, we have built upon that work to test: 1. seasonal differences, 2. the influence of environmental factors and 3. the influence of anthropogenic development (e.g. river‐front houses) on nocturnal basking behaviour. We visually surveyed transects repeatedly at night on the Ross River, Townsville, QLD, Australia from March to November 2020 and documented nocturnal basking in both freshwater turtles (Emydura macquarii krefftii) and freshwater crocodiles (Crocodylus johnstoni). For both taxa, we found significantly more nocturnal basking activity during the hotter months. Likewise, water surface temperature significantly influenced nocturnal basking in both taxa, especially when water temperatures were both high and warmer than air temperatures. We propose that nocturnal basking provides a mechanism for thermoregulatory cooling when water temperatures are high (e.g. 30°C) and above‐preferred temperatures. After accounting for availability in basking habitat, both turtles and crocodiles basked more frequently on the undeveloped side of the river, suggesting avoidance of human activity or disturbance. This study is the first to document nocturnal basking activity temporally throughout the year as well as the first to identify the influences of environmental factors. Nocturnal thermoregulation has been documented in many reptiles, however, thermoregulatory cooling in tropical systems is less well‐known.

show abstract