Pacific Turtle Tracks: Grupo Tortuguero

Data provider
Grupo Tortuguero Tracking Project
Originating data center
Satellite Tracking and Analysis Tool (STAT)

The oceanic movements of loggerhead turtles (Caretta caretta), green turtles (Chelonia mydas), and a Pacific ridley turtle (Lepidochelys olivacea) were monitored with satellite telemetry between 1996 and 2001 in the Pacific Ocean. During this time several turtles migrated across the Pacific Ocean, covering more than 11,500 km between Santa Rosaliita, Baja California, Mexico (28 40N, 114 14W), and Sendai Bay, Japan (37 54N, 140 56E). These findings are consistent with the hypothesis that loggerheads feeding in the eastern Pacific eventually return to nest on western Pacific beaches. Baja California loggerhead turtles have been shown, through molecular genetic analysis (Bowen et al. 1995) and flipper tag returns (Uchida and Teruya 1988, Resendiz et al. 1998), to be primarily of Japanese origin. We conclude that loggerhead turtles are capable of transpacific migrations and propose that the band of water between 25 and 30 degrees North latitude, the Subtropical Frontal Zone, may be an important transpacific migratory corridor. Recent findings (Polovina et al. 2000) indicate that juvenile loggerheads in the North Pacific move westward against weak (0.1-0.3 km/hr) eastward geostrophic currents, demonstrating that passive drift may not entirely explain the dispersal of loggerheads.

Juvenile loggerhead turtles, Caretta caretta, in the 20 - 85 cm straight carapace length (SCL) size range have been observed in the offshore waters along the Pacific coast of California, USA, and the Baja California peninsula, Mexico (Pitman 1990, Nichols, in press). Bartlett (1989) suggested that these turtles might be of western Pacific origin, migrating 10,000 km and feeding on pelagic red crabs (Pleuroncodes planipes) along the Baja California coast. Subsequently, Pacific loggerheads appear to utilize the entire North Pacific during the course of development in a manner similar to Atlantic loggerheads' use of the Atlantic Ocean (Bolten et al. 1998). After a period of more than 10 years (Zug et al. 1995), mature turtles evidently cross the Pacific Ocean from pelagic waters and foraging areas along the Baja California coast to return to natal beaches, a journey of more than 12,000 km in each direction. This is the first effort to document pelagic movements of North Pacific loggerheads from feeding grounds to nesting areas using satellite telemetry. Previous telemetry studies of loggerhead turtles have documented post-reproductive movements (Stoneburner 1982), pelagic movements (Polovina et al. 2000), home ranges (Renaud and Carpenter 1994), navigational abilities (Papi et al. 1997) and homing behavior (Luschi 1996). However, few studies of sea turtles have documented pre-nesting movements from feeding grounds to breeding areas. Notably, Renaud and Landry (1996) documented movement of a Kemp's ridley turtle (Lepidochelys kempii) from feeding grounds in Louisiana, USA, to its successful nesting in Rancho Nuevo, Mexico. A unique opportunity to track the movements of an adult-sized loggerhead turtle, rarely encountered along the Baja California coast, emerged in 1996. The turtle had been raised in captivity and used in the initial genetic analysis of Baja California loggerhead turtles (Bowen et al., 1995). Its mature size (Kamezaki and Matsui, 1997), genetic affinities with Japanese turtles, and the existence of a previous tag return from Japanese waters of a captive-raised, Baja California loggerhead turtle (Resendiz et al., 1998) were the deciding factors in choosing this particular turtle for the study. This turtle is included in the dataset as series 7667, named Adelita. The objective of the study was to monitor the oceanic movement, using satellite telemetry, of a Pacific loggerhead turtle initially captured on feeding grounds along the Baja California coast. Movement data also were examined with respect to oceanographic and meteorological information in an effort to gain insight into the navigational cues that guide adult sea turtles and to identify possible transpacific movement corridors.

The objective of the study was to monitor the oceanic movement, using satellite telemetry, of a Pacific loggerhead turtle initially captured on feeding grounds along the Baja California coast. Movement data also were examined with respect to oceanographic and meteorological information in an effort to gain insight into the navigational cues that guide adult sea turtles and to identify possible transpacific movement corridors.

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Overview

Attributes described below represent those in the original dataset provided by the provider.
Only minimum required attributes are visible and downloadable online. Other attributes may be obtained upon provider's permission.

Attributes in dataset

Attribute (table column)	Description
prognum	Program number
tag_id	PTT ID
lc	Location class
iq	Quality indicator
dir1	Dir 1
nb_mes	Number of messages received
big_nb_mes	definition not provided
best_level	Best signal strength in dB
pass_duration	Pass duration in seconds
nopc	Number Of Plausibility Checks successful (from 0-4)
calcul_freq	Calculated frequency
altitude	Altitude used for location calculation
sensors	Sensors
species	Species name
project_id	STAT Project ID
lc_filter	Parameters to location filtering
speed_filter	Parameters to speed filtering
distance_filter	Parameters to distance filtering
topo_filter	Parameters to topo filtering
time_filter	Parameters to time filtering
angle_filter	Parameters to angle filtering
life_stage	Life stage of the animal
gender	Gender of the animal
wetdry	Wet or dry
wetdry_filter	Parameters to Wet or dry filterint
obs_datetime	Date and time (local time zone)
timezone_h	Time difference from UTC