Denise M. Parker

Post-Nesting Migrations of Leatherback Turtles (Dermochelys coriacea) from Jamursba-Medi, Bird's Head Peninsula, Indonesia

ABSTRACT Nine leatherback turtles (Dermochelys coriacea) were tracked for 111–695 days via satellite telemetry from one of the largest remaining western Pacific leatherback turtle nesting beaches, Jamursba-Medi, Papua, Indonesia. The turtles moved into tropical waters of the Philippines and Malaysia, into the Sea of Japan, and across the equatorial Pacific to temperate waters off North America. This study provides the first record of a trans-Pacific migration by a leatherback turtle.

A Model of Loggerhead Sea Turtle ( Caretta caretta ) Habitat and Movement in the Oceanic North Pacific

Habitat preferences for juvenile loggerhead turtles in the North Pacific were investigated with data from two several-year long tagging programs, using 224 satellite transmitters deployed on wild and captive-reared turtles. Animals ranged between 23 and 81 cm in straight carapace length. Tracks were used to investigate changes in temperature preferences and speed of the animals with size. Average sea surface temperatures along the tracks ranged from 18 to 23 °C. Bigger turtles generally experienced larger temperature ranges and were encountered in warmer surface waters. Seasonal differences between small and big turtles suggest that the larger ones dive deeper than the mixed layer and subsequently target warmer surface waters to rewarm. Average swimming speeds were under 1 km/h and increased with size for turtles bigger than 30 cm. However, when expressed in body lengths per second (bl s−1), smaller turtles showed much higher swimming speeds (>1 bl s −1) than bigger ones (0.5 bl s−1). Temperature and speed values at size estimated from the tracks were used to parameterize a habitat-based Eulerian model to predict areas of highest probability of presence in the North Pacific. The model-generated habitat index generally matched the tracks closely, capturing the north-south movements of tracked animals, but the model failed to replicate observed east-west movements, suggesting temperature and foraging preferences are not the only factors driving large-scale loggerhead movements. Model outputs could inform potential bycatch reduction strategies.

Migrations of green turtles in the central South Pacific

Migrations of seven post-nesting green turtles at Rose Atoll (American Samoa) were tracked by satellite transmitters in 1993–1995. Most turtles migrated 1600 km to foraging areas in Fiji and occupied home ranges averaging 27 km 2 . Additional tag recaptures from other studies indicate a common pattern of turtle movement in the central South Pacific region. In total, the 26 recaptures of primarily post-nesting turtles from French Polynesia, American Samoa, and Cook Islands showed a similar course of direction and destination: 96% migrated westward after nesting, with 58% going specifically to Fiji. We propose that this pattern reflects the lower availability of turtle food east of Fiji where most islands are small, steep and have limited areas suitable for seagrass or algal growth. In contrast, Fiji’s extensive pastures of seagrass and algae appear to be a significant resource for many green turtles in the region. These turtles apparently spend most of their adult life in Fijian waters, taking only brief migrations to other islands to nest. # 2003 Elsevier Ltd. All rights reserved.

Beach Use, Internesting Movement, and Migration of Leatherback Turtles, Dermochelys coriacea, Nesting on the North Coast of Papua New Guinea

ABSTRACT Internesting and migratory movements of female leatherback turtles (Dermochelys coriacea) from Kamiali Wildlife Management Area were tracked by satellite telemetry during the 2001–2002 and 2002–2003 nesting seasons, and an aerial survey of nearly 2800 km of the north Papua New Guinea coastline and New Britain Island was conducted during January 2004. Nesting occurred during November–March at the Kamiali Wildlife Management Area monitoring beach with peak activity during December–January. Telemetry results indicated that nesting females used Huon Gulf waters adjacent to the nesting beach and renested inside and outside the protected area within the Kamiali Wildlife Management Area. After nesting, the turtles migrated over deep waters in a southeastern direction to high latitude waters of the South Pacific Ocean.

Short-Range Movements of Hawksbill Turtles ( Eretmochelys imbricata ) from Nesting to Foraging Areas within the Hawaiian Islands

Abstract: Hawksbill sea turtles, Eretmochelys imbricata, reside around the main Hawaiian Islands but are not common. Flipper-tag recoveries and satellite tracking of hawksbills worldwide have shown variable distances in post-nesting travel, with migrations between nesting beaches and foraging areas ranging from 35 to 2,425 km. Nine hawksbill turtles were tracked within the Hawaiian Islands using satellite telemetry. Turtles traveled distances ranging from 90 to 345 km and took between 5 to 18 days to complete the transit from nesting to foraging areas. Results of this study suggest that movements of Hawaiian hawksbills are relatively short-ranged, and surveys of their foraging areas should be conducted to assess status of the habitat to enhance conservation and management of these areas.

GEOGRAPHIC VARIATION IN MARINE TURTLE FIBROPAPILLOMATOSIS

Abstract We document three examples of fibropapillomatosis by histology, quantitative polymerase chain reaction (qPCR), and sequence analysis from three different geographic areas. Tumors compatible in morphology with fibropapillomatosis were seen in green turtles from Puerto Rico and San Diego (California) and in a hybrid loggerhead/ hawksbill turtle from Florida Bay (Florida). Tumors were confirmed as fibropapillomas on histology, although severity of disease varied between cases. Polymerase chain reaction (PCR) analyses revealed infection with the fibropapilloma-associated turtle herpesvirus (FPTHV) in all cases, albeit at highly variable copy numbers per cell. Alignment of a portion of the polymerase gene from each fibropapilloma-associated turtle herpesvirus isolate demonstrated geographic variation in sequence. These cases illustrate geographic variation in both the pathology and the virology of fibropapillomatosis.

“Going with the Flow” or Not: Evidence of Positive Rheotaxis in Oceanic Juvenile Loggerhead Turtles ( Caretta caretta ) in the South Pacific Ocean Using Satellite Tags and Ocean Circulation Data

The movement of juvenile loggerhead turtles (n = 42) out-fitted with satellite tags and released in oceanic waters off New Caledonia was examined and compared with ocean circulation data. Merging of the daily turtle movement data with drifter buoy movements, OSCAR (Ocean Surface Current Analyses - Real time) circulation data, and three different vertical strata (0–5 m, 0–40 m, 0–100 m) of HYCOM (HYbrid Coordinate Ocean Model) circulation data indicated the turtles were swimming against the prevailing current in a statistically significant pattern. This was not an artifact of prevailing directions of current and swimming, nor was it an artifact of frictional slippage. Generalized additive modeling was used to decompose the pattern of swimming into spatial and temporal components. The findings are indicative of a positive rheotaxis whereby an organism is able to detect the current flow and orient itself to swim into the current flow direction or otherwise slow down its movement. Potential mechanisms for the means and adaptive significance of rheotaxis in oceanic juvenile loggerhead turtles are discussed.

Active dispersal in loggerhead sea turtles (Caretta caretta) during the 'lost years'.

Highly migratory marine species can travel long distances and across entire ocean basins to reach foraging and breeding grounds, yet gaps persist in our knowledge of oceanic dispersal and habitat use. This is especially true for sea turtles, whose complex life history and lengthy pelagic stage present unique conservation challenges. Few studies have explored how these young at-sea turtles navigate their environment, but advancements in satellite technology and numerical models have shown that active and passive movements are used in relation to open ocean features. Here, we provide the first study, to the best of our knowledge, to simultaneously combine a high-resolution physical forcing ocean circulation model with long-term multi-year tracking data of young, trans-oceanic North Pacific loggerhead sea turtles during their ‘lost years’ at sea. From 2010 to 2014, we compare simulated trajectories of passive transport with empirical data of 1–3 year old turtles released off Japan (29.7–37.5 straight carapace length cm). After several years, the at-sea distribution of simulated current-driven trajectories significantly differed from that of the observed turtle tracks. These results underscore current theories on active dispersal by young oceanic-stage sea turtles and give further weight to hypotheses of juvenile foraging strategies for this species. Such information can also provide critical geographical information for spatially explicit conservation approaches to this endangered population.

Multi-year tracking reveals extensive pelagic phase of juvenile loggerhead sea turtles in the North Pacific

BackgroundThe juvenile stage of loggerhead sea turtles (Caretta caretta) can last for decades. In the North Pacific Ocean, much is known about their seasonal movements in relation to pelagic habitat, yet understanding their multi-year, basin-scale movements has proven more difficult. Here, we categorize the large-scale movements of 231 turtles satellite tracked from 1997 to 2013 and explore the influence of biological and environmental drivers on basin-scale movement.ResultsResults show high residency of juvenile loggerheads within the Central North Pacific and a moderate influence of the Earth’s magnetic field, but no real-time environmental driver to explain migratory behavior.ConclusionsWe suggest the Central North Pacific acts as important developmental foraging grounds for young juvenile loggerhead sea turtles, rather than just a migratory corridor. We propose several hypotheses that may influence the connectivity between western and eastern juvenile loggerhead foraging grounds in the North Pacific Ocean.

Tracking Male Loggerhead Turtle Migrations Around Southwestern Japan Using Satellite Telemetry

Abstract Three satellite-tagged male loggerhead turtles (Caretta caretta) were released from the coastal waters of Satsuma Peninsula, Kyusyu, southwestern Japan (lat 31°42′N, long 130°18′E), and their movements were tracked for up to 449 d. Total distance traveled by the turtles ranged from 1540 to 5519 km. The turtles remained mainly along the coast and islands of the East China Sea and the Sea of Japan, except for spending a brief period of time (1–30 d) in the open ocean. The long-distance movement followed a seasonal pattern, evidently triggered by fluctuations in sea surface temperature.