Substrate influences human removal of freshwater turtle nests in the eastern Brazilian Amazon

Itxaso Quintana,Darren Norris,Fernanda Michalski,James P Gibbs,Andressa Valerio

doi:10.1038/s41598-020-65074-1

Abstract

Substrate type determines nesting success and fitness in turtles and is a critical consideration for nesting area protection and restoration. Here, we evaluated the effect of substrate on nest removal by humans in the eastern Brazilian Amazon. We analyzed substrate composition and fate of 216 P. unifilis nests along 88 km of rivers. River segment and substrate type were the most important predictors of nest removal by humans. We found up to 36% lower removal of nests in fine sand and experimental results support the hypothesis that wind more often obscures tracks of nesting females in substrates with more (>66%) fine sand. Our findings are useful for informing the restoration of artificial nesting areas across the Amazon, as nesting area substrates should be selected not only to maintain hatchling sex ratios, but also to minimize nest removal by humans.

Highlights

Substrate type determines nesting success and fitness in turtles and is a critical consideration for nesting area protection and restoration
Considering the importance of nest-site selection, the restoration of nesting habitat could be expected to increase P. unifilis populations, there remains a lack of information to effectively develop restoration actions
We examined grain size of substrate particles found in P. unifilis nests to identify substrate associations with nest removal by humans and guide restoration of nesting areas after dam establishment across the Amazon

Summary

Introduction

Substrate type determines nesting success and fitness in turtles and is a critical consideration for nesting area protection and restoration. P. unifilis is a widespread freshwater species found across the Amazon, North Atlantic and Orinoco river basins[27,28]. This is a relatively large species (females can weight up to 12 kg) that has been exploited since the pre-colonial period (pre 18th century) and is still widely consumed by indigenous and riverine peoples across Amazonia[4,20,29]. Considering the importance of nest-site selection, the restoration of nesting habitat could be expected to increase P. unifilis populations, there remains a lack of information (including the nature of nesting substrates associated with nesting success) to effectively develop restoration actions

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