Extreme rainfall events and cooling of sea turtle clutches: Implications in the face of climate warming.

Graeme C. Hays,David T. Booth,Jamie N. Tedeschi,Jacques‐Olivier Laloë,Andy Dunstan,Ian Bell,Richard D. Reina

doi:10.1002/ece3.7076

Abstract

Understanding how climate change impacts species and ecosystems is integral to conservation. When studying impacts of climate change, warming temperatures are a research focus, with much less attention given to extreme weather events and their impacts. Here, we show how localized, extreme rainfall events can have a major impact on a species that is endangered in many parts of its range. We report incubation temperatures from the world's largest green sea turtle rookery, during a breeding season when two extreme rainfall events occurred. Rainfall caused nest temperatures to drop suddenly and the maximum drop in temperature for each rain‐induced cooling averaged 3.6°C (n = 79 nests, min = 1.0°C, max = 7.4°C). Since green sea turtles have temperature‐dependent sex determination, with low incubation temperatures producing males, such major rainfall events may have a masculinization effect on primary sex ratios. Therefore, in some cases, extreme rainfall events may provide a “get‐out‐of‐jail‐free card” to avoid complete feminization of turtle populations as climate warming continues.

Highlights

Sea turtles are an iconic group with temperature-dependent sex determination (TSD), where the sex of an individual is determined by the temperature experienced during the thermosensitive period (TSP) while eggs are incubating (Miller, 1997)
Previous studies have focused on the cooling effect seasonal precipitation patterns have on reproductive success and primary sex ratios (e.g., Laloë and Esteban et al, 2015; Lolavar & Wyneken, 2015)
We assumed that precipitation recorded at the nearest weather station is representative of precipitation at our field site, given the synchronicity of temperature drops in our study nests with extreme rainfall events recorded at the nearest weather station

Summary

| INTRODUCTION

Sea turtles are an iconic group with temperature-dependent sex determination (TSD), where the sex of an individual is determined by the temperature experienced during the thermosensitive period (TSP) while eggs are incubating (Miller, 1997). A serious threat to sea turtles is that climate warming is raising incubation temperatures of nests and so causing increasing feminization of hatchling sex ratios (Glen & Mrosovsky, 2004; Hays et al, 2003; Jensen et al, 2018) as well as increasing hatchling mortality (Laloë et al, 2017; Monsinjon et al, 2019; Pike, 2014). The extreme female-biased sex ratio skew at this rookery was highlighted (Jensen et al, 2018), with >99% of juvenile turtles being females. At this globally important rookery, climate warming and entire feminization of the hatchling production is a grave threat

| METHODS

| DISCUSSION