148
The Biology of Sea Turtles, Vol. II
output than those residing in less than optimal foraging areas? Is there a relationship
between the average body size of individual nesting females (or reproductive
history) with the number of females breeding for the year at a particular rookery
or population?
Unfortunately, quantitative data do not exist to investigate these questions for
most species. However, in Southern Queensland (Australia) female C. caretta
foraging at Heron Island begin migration to nest at Mon Repos approximately 2
weeks earlier than those from the more distant and southern areas in Moreton Bay
(Limpus, 1985). With regard to growth rates, density-dependent growth has been
reported in Caribbean C. mydas populations (Bjorndal et al., 2000), and growth
rates in southern Queensland populations appear to be related to ENSO climatic
events (Limpus and Chaloupka, 1997). Specifically, female C. mydas at Moreton
Bay have faster growth rates and obtain a larger size at maturity than females in
Shoalwater Bay and Heron Reefs (Chaloupka et al., in press). It is presumed that
resource (energy) acquisition is one factor that influences growth rates and breeding
frequencies in presexually mature and mature turtles, respectively. Whether turtles
with faster growth rates (presexual maturity) differ in their age and size at maturity
or have different breeding rates is unknown. Limited data suggest that female C.
caretta residing at Heron Island have a remigration interval 1.5 years longer than
those females that nest at the same rookeries and reside in Moreton Bay, some 560
km into higher latitudes (Limpus, 1985). The continuation of long-term monitoring
studies investigating reproductive cycles, in addition to the quantification of gender,
age class, and reproductive output for these populations, may lead to definitive
answers to these questions.
Seasonal reproductive output appears to be dependent on length of the breeding
season and the breeding history of the individual. Although for C. mydas, C.
caretta, and N. depressus, experienced breeders (remigrants) were larger than firsttime breeders (neophytes) (Limpus, 1985; Parmenter and Limpus, 1995; Limpus
et al., 2001a; Hamann, 2002), no significant difference in body size was found
between experienced and first-time breeding D. coriacea (Tucker and Frazer,
1991). Reproductive output (number of clutches laid in a season) has been correlated with when a female first arrived at the nesting beach for the breeding season,
with early arrivals laying more clutches (C. mydas: Limpus et al., 2001a). Interestingly, in some populations of C. mydas and D. coriacea, experienced breeders
arrived earlier at the nesting beach than presumed first-time breeders (C. mydas:
Hamann, 2002; D. coreacea: Tucker and Frazer, 1991). In contrast, in some
populations the presumed first-time breeders appeared to arrive earlier in the season
(C. mydas: Bjorndal and Carr, 1989). Additionally, experienced breeders have been
recorded laying more clutches of eggs for the season than presumed first-time
breeders (C. mydas: Carr et al., 1978; Bjorndal and Carr, 1989; Hamann, 2002;
C. caretta: Limpus, 1985; D. coriacea: Tucker and Frazer, 1991).
Several hypotheses may account for the low reproductive output of first-time
breeders. First, they may recruit fewer follicles for the first breeding season. Second,
some animals, especially those that arrive late in the nesting season, may be interrupted by proximate environmental conditions such as a thermal constraint, or
sporadic exogenous conditions that prevent continued nesting later in the season.
1123 book.book Page 148 Thursday, November 14, 2002 11:50 AM
The Biology of Sea Turtles, Vol. II
output than those residing in less than optimal foraging areas? Is there a relationship
between the average body size of individual nesting females (or reproductive
history) with the number of females breeding for the year at a particular rookery
or population?
Unfortunately, quantitative data do not exist to investigate these questions for
most species. However, in Southern Queensland (Australia) female C. caretta
foraging at Heron Island begin migration to nest at Mon Repos approximately 2
weeks earlier than those from the more distant and southern areas in Moreton Bay
(Limpus, 1985). With regard to growth rates, density-dependent growth has been
reported in Caribbean C. mydas populations (Bjorndal et al., 2000), and growth
rates in southern Queensland populations appear to be related to ENSO climatic
events (Limpus and Chaloupka, 1997). Specifically, female C. mydas at Moreton
Bay have faster growth rates and obtain a larger size at maturity than females in
Shoalwater Bay and Heron Reefs (Chaloupka et al., in press). It is presumed that
resource (energy) acquisition is one factor that influences growth rates and breeding
frequencies in presexually mature and mature turtles, respectively. Whether turtles
with faster growth rates (presexual maturity) differ in their age and size at maturity
or have different breeding rates is unknown. Limited data suggest that female C.
caretta residing at Heron Island have a remigration interval 1.5 years longer than
those females that nest at the same rookeries and reside in Moreton Bay, some 560
km into higher latitudes (Limpus, 1985). The continuation of long-term monitoring
studies investigating reproductive cycles, in addition to the quantification of gender,
age class, and reproductive output for these populations, may lead to definitive
answers to these questions.
Seasonal reproductive output appears to be dependent on length of the breeding
season and the breeding history of the individual. Although for C. mydas, C.
caretta, and N. depressus, experienced breeders (remigrants) were larger than firsttime breeders (neophytes) (Limpus, 1985; Parmenter and Limpus, 1995; Limpus
et al., 2001a; Hamann, 2002), no significant difference in body size was found
between experienced and first-time breeding D. coriacea (Tucker and Frazer,
1991). Reproductive output (number of clutches laid in a season) has been correlated with when a female first arrived at the nesting beach for the breeding season,
with early arrivals laying more clutches (C. mydas: Limpus et al., 2001a). Interestingly, in some populations of C. mydas and D. coriacea, experienced breeders
arrived earlier at the nesting beach than presumed first-time breeders (C. mydas:
Hamann, 2002; D. coreacea: Tucker and Frazer, 1991). In contrast, in some
populations the presumed first-time breeders appeared to arrive earlier in the season
(C. mydas: Bjorndal and Carr, 1989). Additionally, experienced breeders have been
recorded laying more clutches of eggs for the season than presumed first-time
breeders (C. mydas: Carr et al., 1978; Bjorndal and Carr, 1989; Hamann, 2002;
C. caretta: Limpus, 1985; D. coriacea: Tucker and Frazer, 1991).
Several hypotheses may account for the low reproductive output of first-time
breeders. First, they may recruit fewer follicles for the first breeding season. Second,
some animals, especially those that arrive late in the nesting season, may be interrupted by proximate environmental conditions such as a thermal constraint, or
sporadic exogenous conditions that prevent continued nesting later in the season.
1123 book.book Page 148 Thursday, November 14, 2002 11:50 AM