Nest removal by humans creates an evolutionary trap for Amazonian freshwater turtles

• Published in: Journal of zoology (1987) Vol. 309; no. 2; pp. 94 - 105
• Main Authors: Quintana, I., Norris, D., Valerio, A., Becker, F. G., Gibbs, J. P., Michalski, F.
• Format: Journal Article
• Language: English
• Published: London Blackwell Publishing Ltd 01.10.2019
• Subjects: Animal embryos; Breeding sites; egg harvesting; Eggs; Embryos; Females; Fitness; Freshwater; Freshwater tortoises; Harvesting; human impact; Inland water environment; nest site choice; Nesting; nesting habitat; Offspring; Oviparity; oviparous; Oviposition; Podocnemis unifilis; Reproductive fitness; Reproductive strategy; Reptiles & amphibians; Rivers; Site selection; turtle conservation; Turtles
• ISSN: 0952-8369; 1469-7998
• DOI: 10.1111/jzo.12689

Nest‐site selection exerts a fundamental maternal effect on offspring fitness in oviparous species. In many freshwater turtles, females do not care for their eggs after oviposition but rather rely on a nest's micro‐environment to incubate developing embryos although linkages between oviposition choices and overall fitness remain poorly evaluated. We tested predictions derived from multiple hypotheses to examine nesting patterns of the yellow‐spotted river turtle Podocnemis unifilis, a species imperiled by egg harvesting by humans throughout its range, based on data collected from 73 nesting sites along 118 km of river in the eastern Brazilian Amazon. Nesting area size largely explained nest‐site selection by turtles, but only weakly explained turtle egg harvesting by humans. Despite the wide availability of alternative nesting habitats, turtles do not appear to be capable of avoiding hazardous nesting sites associated with increased egg harvesting by humans. Because signals used by female turtles to select nesting areas are apparently not sufficient for avoiding nesting along rivers accessible to humans, direct conservation action will be vital for persistence of these and likely other Amazonian freshwater turtles. Avoiding predators is important for the survival of prey species and turtles have evolved a number of characteristics that have protected them over millennia. However, human hunting of adults and eggs is threatening many freshwater turtle populations. The Yellow‐spotted River Turtle (Podocnemis unifilis) is widespread across the Amazon Basin, but like many other turtles their populations have been decimated by humans. Both eggs and adults of P. unifilis have been exploited since the pre‐colonial period (pre 18th century) and are still consumed by indigenous and riverine communities across Amazonia. Although the Yellow‐spotted River Turtle has been widely studied over decades it remains unclear if they have any behavior or response that can help the members of surviving populations avoid predation by humans. To understand if female Yellow‐spotted River Turtles were able to avoid human hunting we monitored 73 nesting sites along 118 km of rivers in the eastern Brazilian Amazon. We found that despite the wide availability of alternative nesting habitats, turtles do not appear to be capable of avoiding hazardous nesting sites associated with increased egg harvesting by humans. Because signals used by female turtles to select nesting areas are apparently not sufficient for avoiding nesting along rivers accessible to humans, direct conservation action will be vital for persistence of these and likely other Amazonian freshwater turtles.