Hydrological Effects on the Reproduction of the Giant South American River Turtle Podocnemis expansa (Testudines: Podocnemididae)

Understanding the relationship between species and the environment is crucial to predicting their responses to human-induced global changes, i.e., habitat conversion, biological invasions, and global warming. Precipitation and river level are relevant factors that regulate the populations of aquatic organisms. We used long-term data to assess the effects of climate on nest number, clutch size (number of eggs per nest), hatching success, and unviable eggs of the Giant South American River Turtle (Podocnemis expansa) in a protected area of Brazilian Amazonia. We found a positive relationship between the number of nests and precipitation on headwaters in May. We also observed that clutch size increased when the local river level rose; hatching success increased with rising local river level, mainly during October and November; and egg failure increased with rising headwater river level. We show how precipitation and river level (at local and headwater) can influence reproductive success in P. expansa, highlighting the perils of human-induced environmental changes.