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

Intro to the article

By Dr Beck

Gaping in ‘Salties’ has been scientifically observed since at least Steve Irwin in Australia became curious about the mechanisms which triggered it. My own friend, Dr Heather A. Stewart, took up the challenge later with “Unprovoked Mouth Gaping Behavior in Extant Crocodylia‬”. Now, one of the most definitive studies done, accomplished in South Africa, is presented here citing Heather’s previous work

By CormacPricea1Mohamed AEzatabCélineHanzena2Colleen TDownsa3aCentre for Functional Biodiversity, School of Life Sciences, University of KwaZulu-Natal, Private Bag X01, Scottsville, Pietermaritzburg, 3209, South AfricabWildlife Ecology and Conservation Group and Behavioural Ecology Group, Wageningen University, the Netherlands. Received 31 August 2022, Revised 14 October 2022, Accepted 24 October 2022, Available online 29 October 2022.


“Gaping is a regularly observed behaviour in crocodilians globally but is still poorly understood in relation to external variables which could trigger this behaviour. The occurrence of gaping behaviour was investigated in a large wild population of Nile crocodiles (Crocodylus niloticus) during the dry and wet seasons at Nyamithi Pan, Ndumo Game Reserve, South Africa.

“This is one of the longest crocodile gaping behaviour studies conducted in the wild, with 300 h of observations conducted over two seasons resulting in 1120 gaping behaviours recorded. The most common size class observed was between 1.5-2.5 m (n = 697), which accounted for 62.2% of the gaping observations. A significant decrease in gaping duration was observed as ambient temperatures increased, and the gape duration was longer at a higher degree angle. In addition, an increase in gape duration was observed as the number of neighbouring crocodiles increased. These results suggest gaping behaviour occurs when there are other crocodiles nearby and when temperatures do not necessitate thermoregulation. The study suggests that gaping could be used as a form of thermoregulation and intra-species communication…”

Bahaviour Processes