Sea Turtle Recovery Action Plan for St. Kitts and Nevis - WIDECAST

St. Kitts and Nevis Sea Turtles…
2.2 Chelonia mydas, Green Sea Turtle
Local common names for the species include "green turtle" and "green-back". The green
turtle is recognized by a round, blunt beak with serrated cutting edges, one pair of enlarged
scales between the eyes, and four pairs of lateral carapace scutes that do not overlap as they do
on the hawksbill (cf. section 2.4) (Figure 3). The shell colour is light to dark brown, sometimes
shaded with olive, with radiating wavy or mottled markings of darker colour or with large
blotches of dark brown. It is generally devoid of barnacles. The plastron (=belly plate) is
whitish or light yellow (Carr, 1952). Adults can attain weights of 230 kg (500 lb) (Pritchard et
al., 1983) and generally measure 95-120 cm in straight carapace length (nuchal notch to posterior
tip); a mean size of 100.2 cm (n=2107) is reported from the Caribbean nesting beach at
Tortuguero, Costa Rica (Bjorndal and Carr, 1989). Audra Barrett measured seven carapaces
from young green turtles killed on Nevis in 1986; they averaged 68 cm total curved carapace
length (range 57-75 cm) (Wilkins and Barrett, 1987). Individuals of varying sizes are present in
the waters surrounding St. Kitts/Nevis throughout the year.
It is quite certain that individual green turtles do not remain in local waters throughout
their lives. Hatchlings emerge from their nests, scurry to the sea, orient offshore in a swimming
frenzy that persists over a period of days, and ultimately enter an offshore convergence or weed
line. It is well known, for example, that Sargassum seaweed rafts shelter hatchling green turtles
and also harbour a diverse, specialized fauna, including many kinds of little fishes, crustaceans,
worms, mollusks, tunicates, and coelenterates; these may provide food for the young turtles
(Carr, 1987a). The turtles remain epipelagic (surface dwelling in the open sea) for an unknown
period of time (perhaps 1-3 years) before taking up residence in continental shelf habitats.
Upon leaving the open sea existence that characterises their earliest years, green turtles
become herbivores and remain so for the rest of their lives (Bjorndal, 1985). In the Caribbean
Sea, green turtles feed primarily on the sea grass Thalassia testudinum (Bjorndal, 1982),
commonly referred to as "turtle grass". Field studies indicate that individual turtles maintain
feeding "scars" by returning to the same area of sea grass meadow to forage each day (Ogden et
al., 1980, 1983). These scars, or grazing plots, are maintained by regular cropping for several
months and the more digestible newer growth (higher in protein, lower in lignin) is preferred
(Bjorndal, 1980). When the cropped grasses show signs of stress (blade thinning, increased
inter-nodal distance), the turtle apparently abandons the scar and moves on to form another.
Green turtles travel extensively during the first decades of their lives and in the years
preceding reproductive maturity take up temporary residence in many locations (Carr et al.,
1978). They may travel thousands of kilometers in the Caribbean Sea before the urge to
repro-duce impels them to migrate to mating and nesting grounds, the latter presumed to be their
natal (=birth) beach. Caribbean green turtles reach sexual maturity at an estimated 18-36 years
of age (reviewed by Frazer and Ladner, 1986). After reproducing, there is some evidence that
turtles return to resident foraging grounds (=feeding areas). Therefore, the movements of adult
turtles are likely to be less extensive than those of juveniles, since adults move seasonally
between relatively fixed feeding and breeding areas.
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