232
The Biology of Sea Turtles, Vol. II
temporarily inhabit the oceanic zone during migrations from foraging areas to
breeding areas and back. Some of these long-distance reproductive migrations are
spectacular feats, with turtles swimming thousands of kilometers across the open
ocean directly to beaches located on small, isolated oceanic islands (Carr, 1965;
Luschi et al., 1998).
Female green turtles migrate from foraging areas to their natal beaches (Meylan
et al., 1990b) every 2–4 years and show a high degree of nest site fidelity (Miller,
1997). Mating may occur en route to the nesting beach (Meylan et al., 1992), far
from the nesting beach at distant mating grounds (Limpus, 1993), or nearshore the
nesting beach (Carr and Ogren, 1960; Booth and Peters, 1972; Broderick and Godley,
1997; Godley et al., 2002). Females oviposit an average of three clutches at 10- to
17-day intervals (Miller, 1997) and remain near the nesting beach during the
internesting period (Carr et al., 1974; Dizon and Balazs, 1982).
Postnesting females migrate hundreds to thousands of kilometers from their
nesting beach to resident coastal foraging areas (Balazs, 1994; Balazs et al., 1994;
2000; Papi et al., 1995; Schroeder et al., 1996; Cheng and Balazs, 1998; Luschi
et al., 1998; Papi et al., 2000; Luschi et al., 2001). Postbreeding males also migrate
long distances from breeding areas to foraging grounds at the end of the mating
season (Hays et al., 2001a) or may remain in the vicinity of the nesting beach
(Garduno et al., 2000). In general, these migrations can be characterized as relatively
fast, directed movements toward specific locations (Schroeder et al., 1996; Luschi
et al., 1998), which may occur nearshore (Schroeder et al., 1996) or in deep oceanic
water (Balazs, 1994; Luschi et al., 1998), with cohorts traveling along similar pathways during part of the migration (Luschi et al., 2001).
The navigational mechanisms used by green turtles migrating from Ascension
Island to coastal foraging grounds in Brazil have provided insights into the navigational abilities of adult sea turtles. These studies have demonstrated that green turtles
are able to maintain straight courses over long distances in the open ocean (Luschi
et al., 1998), can correct their course during the migration according to environmental information (Luschi et al., 1998), may be guided in part by currents (Luschi et al.,
1998) or windborne information (Luschi et al., 2001), do not rely on sea surface
temperatures (Hays et al., 2001b), and can navigate in the absence of magnetic cues
(Papi et al., 2000).
8.9 EAST PACIFIC GREEN, CHELONIA AGASSIZI
East Pacific green turtles are restricted to the coastal waters, lagoons, and bays along
the west coast of America from Baja California and the Gulf of California to southern
Peru and the Galapagos Islands (Alvarado and Figueroa, 1998), where they feed
primarily on sea grasses and algae (Seminoff et al., 2000).
Females migrate from foraging areas to nesting beaches on average every 3–4
years (Alvarado et al., 2000). The primary nesting beaches are located in Michoacan,
Mexico; however, sporadic nesting also occurs elsewhere along the Mexican and
Central American coast. Mating takes place nearshore the nesting beach (Alvarado
and Figueroa, 1989). Females oviposit between one and seven clutches per season
at 11- to 13-day intervals (Alvarado et al., 2000). Females remain nearshore the
1123 book.book Page 232 Monday, November 11, 2002 11:11 AM
The Biology of Sea Turtles, Vol. II
temporarily inhabit the oceanic zone during migrations from foraging areas to
breeding areas and back. Some of these long-distance reproductive migrations are
spectacular feats, with turtles swimming thousands of kilometers across the open
ocean directly to beaches located on small, isolated oceanic islands (Carr, 1965;
Luschi et al., 1998).
Female green turtles migrate from foraging areas to their natal beaches (Meylan
et al., 1990b) every 2–4 years and show a high degree of nest site fidelity (Miller,
1997). Mating may occur en route to the nesting beach (Meylan et al., 1992), far
from the nesting beach at distant mating grounds (Limpus, 1993), or nearshore the
nesting beach (Carr and Ogren, 1960; Booth and Peters, 1972; Broderick and Godley,
1997; Godley et al., 2002). Females oviposit an average of three clutches at 10- to
17-day intervals (Miller, 1997) and remain near the nesting beach during the
internesting period (Carr et al., 1974; Dizon and Balazs, 1982).
Postnesting females migrate hundreds to thousands of kilometers from their
nesting beach to resident coastal foraging areas (Balazs, 1994; Balazs et al., 1994;
2000; Papi et al., 1995; Schroeder et al., 1996; Cheng and Balazs, 1998; Luschi
et al., 1998; Papi et al., 2000; Luschi et al., 2001). Postbreeding males also migrate
long distances from breeding areas to foraging grounds at the end of the mating
season (Hays et al., 2001a) or may remain in the vicinity of the nesting beach
(Garduno et al., 2000). In general, these migrations can be characterized as relatively
fast, directed movements toward specific locations (Schroeder et al., 1996; Luschi
et al., 1998), which may occur nearshore (Schroeder et al., 1996) or in deep oceanic
water (Balazs, 1994; Luschi et al., 1998), with cohorts traveling along similar pathways during part of the migration (Luschi et al., 2001).
The navigational mechanisms used by green turtles migrating from Ascension
Island to coastal foraging grounds in Brazil have provided insights into the navigational abilities of adult sea turtles. These studies have demonstrated that green turtles
are able to maintain straight courses over long distances in the open ocean (Luschi
et al., 1998), can correct their course during the migration according to environmental information (Luschi et al., 1998), may be guided in part by currents (Luschi et al.,
1998) or windborne information (Luschi et al., 2001), do not rely on sea surface
temperatures (Hays et al., 2001b), and can navigate in the absence of magnetic cues
(Papi et al., 2000).
8.9 EAST PACIFIC GREEN, CHELONIA AGASSIZI
East Pacific green turtles are restricted to the coastal waters, lagoons, and bays along
the west coast of America from Baja California and the Gulf of California to southern
Peru and the Galapagos Islands (Alvarado and Figueroa, 1998), where they feed
primarily on sea grasses and algae (Seminoff et al., 2000).
Females migrate from foraging areas to nesting beaches on average every 3–4
years (Alvarado et al., 2000). The primary nesting beaches are located in Michoacan,
Mexico; however, sporadic nesting also occurs elsewhere along the Mexican and
Central American coast. Mating takes place nearshore the nesting beach (Alvarado
and Figueroa, 1989). Females oviposit between one and seven clutches per season
at 11- to 13-day intervals (Alvarado et al., 2000). Females remain nearshore the
1123 book.book Page 232 Monday, November 11, 2002 11:11 AM