Identification of high-use internesting habitats for eastern Pacific leatherback turtles: role of the environment and implications for conservation

Abstract

The numbers of leatherback turtles Dermochelys coriacea in the eastern Pacific Ocean have declined by up to 90% in the past 2 decades. Initially, egg harvesting was determined to be the largest causative factor, but now that this has been eliminated, high estimated adult mortality from fisheries bycatch poses the single greatest threat to this population. During the nesting season, adult female leatherback turtles nest multiple times and occupy coastal marine habitats near their nesting beaches. In this study, we characterize the interannual variability of high-use internesting habitats used by 44 (out of 46 total) female leatherback turtles that were satellite-tagged at Playa Grande, Costa Rica, from 2004 to 2007. A total of 1135 d of internesting movements were recorded across 3 tracking years. The core 25% utilization distribution (UD) remained predominantly centered within the marine protected area, Parque Nacional Marino Las Baulas (PNMB). The turtles generally dispersed in a northward or southward direction over the shallow continental shelf framing Costa Rica's Nicoya Peninsula. However, there was considerable interannual variation in the shape and area of the larger UD polygons, which was driven by variability in the thermal environment. The maximum swimming speeds and distance traveled from the nesting beach occurred during 2007. Significantly deeper and longer dive durations to cooler temperatures also occurred in this year, which may have been in response to the warming trend from the south driven by the strong Costa Rica Coastal Current. Our findings, therefore, validate the importance of PNMB as a critical habitat for internesting leatherback turtles, but also suggest that a latitudinal expansion of the park is warranted.

Assortative epibiosis of leatherback, olive ridley and green sea turtles in the Eastern Tropical Pacific

“…Different sea turtle species may occupy widely different habitats during the inter-nesting interval (the time between consecutive nesting events in a single nesting season). For example, inter-nesting leatherback turtles tracked from PNMB tended to occupy waters up to 100 km from the nesting beach (Shillinger et al, 2010), whereas olive ridley and green turtles from nearby beaches rarely moved more than 25 and 5 km from the nesting beach respectively (Plotkin et al, 1995;Blanco et al, 2013).…”

Bahamas connection: residence areas selected by breeding female loggerheads tagged in Dry Tortugas National Park, USA

“…Defining these areas can be challenging in the marine environment given their often separate geographic locations, but electronic tags (i.e., satellite, GPS, and geolocation tags) have allowed delineation of high-use at-sea residence sites for marine megafauna, including sea turtles [1][2][3][4][5][6]. Hamann et al [5] ranked efforts to define important in-water habitats as one of the top priorities worldwide for imperiled marine turtles.…”

“…Connections between rookeries and foraging grounds are only now being quantified [2][3][4]11,12]. Loggerhead sea turtles nest every 2-5 years, depositing 2-6 clutches of 75-120 eggs approximately every 2 weeks during the nesting season [13][14][15][16][17][18].…”

Inter-nesting distribution of flatback turtles Natator depressus and industrial development in Western Australia

“…Blumenthal et al 2006, Schofield et al 2013leatherback: e.g. Eckert 2006, Shillinger et al 2010; olive ridley: e.g. Hamel et al 2008).…”