Incorporating Geographical Scale and Multiple Environmental Factors to Delineate the Breeding Distribution of Sea Turtles

Christophe Eizaguirre,Kostas A Katselidis,Liam C Dickson,Gail Schofield

doi:10.3390/drones5040142

Abstract

Temperature is often used to infer how climate influences wildlife distributions; yet, other parameters also contribute, separately and combined, with effects varying across geographical scales. Here, we used an unoccupied aircraft system to explore how environmental parameters affect the regional distribution of the terrestrial and marine breeding habitats of threatened loggerhead sea turtles (Caretta caretta). Surveys spanned four years and ~620 km coastline of western Greece, encompassing low (<10 nests/km) to high (100–500 nests/km) density nesting areas. We recorded 2395 tracks left by turtles on beaches and 1928 turtles occupying waters adjacent to these beaches. Variation in beach track and inwater turtle densities was explained by temperature, offshore prevailing wind, and physical marine and terrestrial factors combined. The highest beach-track densities (400 tracks/km) occurred on beaches with steep slopes and higher sand temperatures, sheltered from prevailing offshore winds. The highest inwater turtle densities (270 turtles/km) occurred over submerged sandbanks, with warmer sea temperatures associated with offshore wind. Most turtles (90%) occurred over nearshore submerged sandbanks within 10 km of beaches supporting the highest track densities, showing the strong linkage between optimal marine and terrestrial environments for breeding. Our findings demonstrate the utility of UASs in surveying marine megafauna and environmental data at large scales and the importance of integrating multiple factors in climate change models to predict species distributions.

Highlights

A major focus of ecological research is how environmental conditions affect the abundance and distribution of animals in both terrestrial and aquatic systems [1,2,3]
Our findings demonstrate the utility of unoccupied aircraft systems (UASs) in surveying marine megafauna and environmental data at large scales and the importance of integrating multiple factors in climate change models to predict species distributions
Our findings demonstrate that UAS technology can be effectively used to survey marine megafauna in relation to environmental data at large scales and could enhance predictions of the spatial responses of species to climate change and future marine protected area (MPA) delineations

Summary

Introduction

A major focus of ecological research is how environmental conditions affect the abundance and distribution of animals in both terrestrial and aquatic systems [1,2,3]. This information is frequently used to predict range shifts in species distributions and to inform management [4,5,6]. The separate and combined effects of those factors on wildlife distributions vary with geographical scale [7,12]. It is important to identify the appropriate combinations of factors that drive the distributions and aggregation hotspots of wildlife and how these factors vary at different scales (from local to regional) to better predict distributions and optimize management strategies [3,13,14]

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Discussion

Conclusion