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School of Life Sciences' Friday Seminar

Dissertation Defense: "From Nesting to Foraging Grounds: Establishing Baseline Spatial Ecology of Green Turtles Tagged in the Mariana Archipelago" Speaker: Josefa Muñoz, PhD Candidate, Marine Biology Graduate Program, ������Ƶ ����ԴDz�. **** Abstract: Green turtles (Chelonia mydas) of the Central West Pacific Distinct Population Segment are listed as Endangered under the U.S. Endangered Species Act, yet have historically been recognized as data-deficient. Baseline spatial ecology remains lacking for the small subpopulation (~100 individuals) nesting in the Mariana Archipelago (MA). This dissertation addresses this knowledge gap by evaluating space use and movements across three adult life-history phases—nesting, post-nesting migration, and foraging—to inform conservation across local and international jurisdictions. From 2014 to 2023, 33 nesting female green turtles in the MA were tracked using satellite telemetry. Autocorrelated kernel density estimation and continuous-time movement modeling were used to quantify core areas (50%) and home ranges (95%) at internesting (time spent in-water between nesting events) and foraging habitats and model post-nesting migration tracks, respectively. These methods were further complemented by dive behavior data, haul-out (beach emergence) records, passive ocean current tracking, and stable carbon (δ¹³C, reflecting foraging habitat) and nitrogen (δ¹⁵N, reflecting trophic position) isotope analysis of bulk skin tissue. During the nesting phase, females exhibited mobile (57%) and restricted (43%) in-water movement patterns, with larger space use occurring off southwestern Guam and most time spent at 10–20 m depths. High nesting beach fidelity was observed in 86% of individuals based on haul-out activity. Following the nesting season, females displayed a bimodal post-nesting migration pattern: 91% undertook long-distance oceanic migrations to foraging grounds across the western Pacific Ocean (East Asia, Southeast Asia, and the Caroline Islands), while 9% remained resident within the MA. Surface drifter trajectories mirrored these migratory routes, suggesting regional ocean currents experienced during early life stages influence adult movement patterns. At foraging destinations, 82% of turtles maintained high site fidelity to a single foraging area, whereas 18% were non-stationary, utilizing multiple sites distanced ≥15 km apart. Foraging turtles generally occupied shallow depths (≤20 m) day and night. Stable isotope analyses—ground-truthed via satellite telemetry—showed preliminary δ¹³C groupings for turtles tracked to primary foraging destinations in the Philippines, Japan, and Micronesia. Meanwhile, consistent δ¹⁵N values across cohorts (mean = 9.3‰; n = 86) suggest that adult female green turtles in this region function predominantly as primary consumers, regardless of foraging location. This dissertation establishes the first comprehensive baseline of spatial ecology for reproductively valuable green turtles of the MA across their entire adult life history. These findings provide a reference point for monitoring future population shifts and offer a conservation framework ranging from local to international scales for this ecologically and culturally significant subpopulation. Zoom: https://hawaii.zoom.us/j/87985219121 (passcode: MBF26SM)

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