Basking and Daily Activity in the Secretive South American Snake‐Necked Turtle in the Wild

Basking is a common activity among ectotherms and especially prevalent in freshwater turtles. In this study, we describe the basking behaviour and thermoconformity of the secretive, fully aquatic South American snake‐necked turtle, Hydromedusa tectifera . We performed monthly diurnal surveys over a total of 12 months during 2019–2021, and seasonal surveys during 2017, in an urban stream of Argentina. We observed 69 basking turtles, almost all of which were in the water in one of three different positions. Basking out of water was very infrequent and typically related to water disturbance and illness. Females and males basked uniformly through the year, while juveniles basked almost exclusively during the warmest months. Water temperature was the best explanatory variable for body temperature, with no significant effect of other environmental or individual turtle variables, confirming the thermoconformity of the species. However, the relationship between water and body temperatures was not strictly proportional. Body temperature was also influenced by site, with basking turtles being slightly warmer than non‐basking individuals, possibly reflecting subtle thermal differences within the stream. Our results revealed that H. tectifera practices daily aquatic basking, likely for purposes other than thermoregulation, which merits further investigation.