Abstract
Environmental factors shape the spatial distribution and dynamics of populations. Understanding how these factors interact with movement behavior is critical for efficient conservation, in particular for migratory species. Adult female green sea turtles, Chelonia mydas, migrate between foraging and nesting sites that are generally separated by thousands of kilometers. As an emblematic endangered species, green turtles have been intensively studied, with a focus on nesting, migration, and foraging. Nevertheless, few attempts integrated these behaviors and their trade‐offs by considering the spatial configurations of foraging and nesting grounds as well as environmental heterogeneity like oceanic currents and food distribution. We developed an individual‐based model to investigate the impact of local environmental conditions on emerging migratory corridors and reproductive output and to thereby identify conservation priority sites. The model integrates movement, nesting, and foraging behavior. Despite being largely conceptual, the model captured realistic movement patterns which confirm field studies. The spatial distribution of migratory corridors and foraging hot spots was mostly constrained by features of the regional landscape, such as nesting site locations, distribution of feeding patches, and oceanic currents. These constraints also explained the mixing patterns in regional forager communities. By implementing alternative decision strategies of the turtles, we found that foraging site fidelity and nesting investment, two characteristics of green turtles' biology, are favorable strategies under unpredictable environmental conditions affecting their habitats. Based on our results, we propose specific guidelines for the regional conservation of green turtles as well as future research suggestions advancing spatial ecology of sea turtles. Being implemented in an easy to learn open‐source software, our model can coevolve with the collection and analysis of new data on energy budget and movement into a generic tool for sea turtle research and conservation. Our modeling approach could also be useful for supporting the conservation of other migratory marine animals.
Highlights
Many species migrate to exploit resources heterogeneously distrib‐ uted in space and time (Jorgensen, Dunlop, Opdal, & Fiksen, 2008)
More recently dispersal affected by oceanic currents and habitat features was modeled for the western Pacific leatherback tur‐ tle (Gaspar & Lalire, 2017), as well as the effect of multiple cues on the homing behavior of individual green sea turtles (Painter & Plochocka, 2019)
Preferred feeding patches will be left in the search of better patches if feeding efficiency falls below a certain threshold; this can happen because too many turtles are feeding on this patch or if regrowth of the forage, sea grass, is slow due to perturbations
Summary
Many species migrate to exploit resources heterogeneously distrib‐ uted in space and time (Jorgensen, Dunlop, Opdal, & Fiksen, 2008). More recently dispersal affected by oceanic currents and habitat features was modeled for the western Pacific leatherback tur‐ tle (Gaspar & Lalire, 2017), as well as the effect of multiple cues on the homing behavior of individual green sea turtles (Painter & Plochocka, 2019) These kinds of IBMs remained focused on movement and did not consider demographic processes such as survival or reproductive output. IBMs were used to represent population dy‐ namics of sea turtles (Mazaris, Broder, & Matsinos, 2006; Mazaris, Fiksen, & Matsinos, 2005; Mazaris & Matsinos, 2006; Piacenza, Richards, & Heppell, 2017), but in these cases, movement was not explicitly implemented Another type of IBMs was used to study nesting population dynamics such as consequences of variable re‐ migration intervals on sea turtles' nesting numbers (Hays, 2000; Neeman, Spotila, & O'Connor, 2015) or how changes in biologi‐ cal processes can influence population recovery and assessments (Piacenza et al, 2017). The model allowed assessing the influence and sensitivity of different foraging and nesting strat‐ egies in concert with feeding patch disturbance on the reproductive output of rookeries
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