The ‘lost years’ of green turtles: using stable isotopes to study cryptic lifestages

Abstract

Ignorance of the location or inaccessible locations of lifestages can impede the study and management of species. We used stable isotopes of carbon and nitrogen to identify the habitats and diets and to estimate the duration of a 'missing' lifestage: the early juvenile stage of the green turtle, Chelonia mydas. Stable isotopes in scute from young herbivorous green turtles in shallow-water habitats revealed that they spend 3-5 years as carnivores in oceanic habitats before making a rapid ontogenetic shift in diet and habitat. Stable isotopes in persistent and continuously growing tissues, such as some fish scales, bird bills and claws and mammal hair and claws, can be used to evaluate the ecology of inaccessible lifestages.

Finding the ‘lost years’ in green turtles: insights from ocean circulation models and genetic analysis

“…Thus, processes that occur in one location may drive changes at distant sites or in other ecosystems through the ecological coupling of long-distance movement [3][4][5]. Gathering such information has proved difficult for species that spend much or all of their time in the open sea, where direct observation is hampered by logistical constraints [4][5][6][7][8]. This is particularly true of young green turtles (Chelonia mydas), which rapidly disperse from natal beaches into the ocean.…”

“…This is particularly true of young green turtles (Chelonia mydas), which rapidly disperse from natal beaches into the ocean. Observations of these turtles are largely lacking during the subsequent life stage termed 'the lost years', and they are generally only seen again three or more years later upon recruiting to near shore foraging grounds (FGs) as juveniles [7,8].…”

Sea Turtles in Florida's Atlantic Waters

“…After an average 2.8-4.6 years (Zug and Glor, 1998;Reich et al, 2007a), green turtles return to developmental habitats within neritic waters, including Florida's east coast (SCL = 20-25 cm, Bjorndal and Bolten, 1988;Bjorndal et al, 2000a;Reich et al, 2007a). Juvenile green turtles are found in Florida's Atlantic waters along nearshore reefs (Wershoven and Wershoven, 1991;Makowski et al, 2006), in coastal lagoons (Mendonça and Ehrhart, 1982;Ehrhart et al, 2007), and to a lesser extent in shipping channels (Henwood and Ogren, 1987).…”

“…Some hatchlings and posthatchling turtles then associate with fl otsam, such as Sargassum communities and downwelling lines (Carr and Meylan, 1980;Witham, 1980;Carr, 1986;Coston-Clements et al, 1991;Witherington, 2002) in oceanic waters. They may remain in oceanic habitats for several years (Carr et al, 1966;Carr, 1987;Collard and Ogren, 1990;Musick and Limpus, 1997;Bjorndal et al, 2000bBjorndal et al, , 2003Reich et al, 2007a).…”

“…We completed a thorough review Ehrhart et al, 2007;Hawkes et al, 2007Hawkes et al, , 2011Arendt et al, 2012a,b,c), satellite telemetry (Blumenthal et al, 2006;Girard et al, 2009;Mansfi eld et al, 2009;Arendt et al, 2012a,b,c;Ceriani et al, 2012), shipboard surveys (Bresette et al, 2010), aerial surveys (Fritts et al, 1983;Schroeder and Thompson, 1987;Epperly et al, 1995Epperly et al, , 2002McClellan, 1996;Witzell and Azarovitz, 1996;Henwood and Epperly, 1999;Goodman et al, 2007), stable isotopes (Reich et al, 2007a, b;Ceriani et al, 2012), and bycatch records (Thompson et al, 1991;Epperly et al, 2002). Mark-recapture via fl ipper or pit tagging provides start and end point data demarking some travels (Meylan, 1995;Schmid and Witzell, 1997;Witzell, 1998;Williams and Frick, 2008).…”