Reproductive Cycles of Males and Females
151
5.5.9.1 Arribadas
Unique to the Lepidochelys genus is a breeding event known commonly as an
arribada (or arribadazon). Briefly, L. kempii and some populations of L. olivacea
exhibit mass nesting events in which large groups of females emerge synchronously
to lay eggs. Generally occurring at night in L. olivacea and during the day in L.
kempii, mass nesting events occur over a period of 1–3 days and reoccur at intervals
of approximately 30 days (see Miller, 1997). Anywhere from 100 to 10,000 or more
females may be involved, and the emerging hypothesis is that this mass nesting
behavior serves as a deterrent for nest predators through “predator satiation” (Eckrich
and Owens, 1995). Although it has been thought of as “socially facilitated nesting”
(Owens et al., 1982), it now appears that these groups of females aggregate for
nesting but disperse randomly during the internesting period. The turtles respond
independently to one or more proximal cues and commence a subsequent arribada
some 30 days later (Plotkin et al., 1995; 1997). Pritchard (1969) hypothesized that
ovulation and egg development would occur at approximately the same time for the
whole arribada cohort, and that females were retaining eggs until suitable emergence
cues arose. Although Lepidochelys spp. have internesting intervals significantly
longer than other species, ovulation still occurs within 2–3 days postoviposition
(Licht et al., 1982; Miller, 1997). Because arribadas are presumed to comprise
several smaller groups of turtles (Plotkin et al., 1995), perhaps prolonged renesting
intervals in arribada females acts to synchronize the final stages of egg development
in as many females as possible. In addition, arribadas may serve to delay oviposition
when conditions are unfavorable (Plotkin et al., 1997).
Although uncommon in other species, Limpus (1985) reports two instances of
prolonged oviducal egg retention (41 and 42 days) in female C. caretta with disabled
hind flippers. Dissection confirmed that in both cases the oviducal eggs were from
the most recent ovulation. Moreover, eggs from one of these females were buried
in an artificial nest and achieved emergence success of 76.2%, providing further
evidence to support Pritchard’s hypothesis that prolonged egg retention occurs to
allow a female to wait for suitable nesting cues.
5.5.9.2 Year-Round Nesting
Nesting seasons for most populations are constrained temporally. However, for most
species, uninterrupted year-round nesting has been recorded at some locations (Witzell, 1983; Marquez, 1994; Hirth, 1997; also see Miller, 1997), although in most of
these cases the majority of nesting activity occurred in a peak period spread over
several months. Bimodal nesting with small and large peak periods has been recorded
for at least one population of D. coriacea; however, relationships between these two
apparently separate cohorts are unknown (Chevalier et al., 1999). Unfortunately,
comprehensive data sets detailing year-round nesting are not available, and thus we
can only speculate reasons to support why and how they persist. Presumably, three
factors control nesting seasonality: (1) the ability to find a mate and successfully
copulate, (2) the suitability of a beach to successfully incubate sea turtle eggs, and
(3) the suitability of the beach to allow efficient offshore dispersal of the hatchlings.
1123 book.book Page 151 Thursday, November 14, 2002 11:50 AM
151
5.5.9.1 Arribadas
Unique to the Lepidochelys genus is a breeding event known commonly as an
arribada (or arribadazon). Briefly, L. kempii and some populations of L. olivacea
exhibit mass nesting events in which large groups of females emerge synchronously
to lay eggs. Generally occurring at night in L. olivacea and during the day in L.
kempii, mass nesting events occur over a period of 1–3 days and reoccur at intervals
of approximately 30 days (see Miller, 1997). Anywhere from 100 to 10,000 or more
females may be involved, and the emerging hypothesis is that this mass nesting
behavior serves as a deterrent for nest predators through “predator satiation” (Eckrich
and Owens, 1995). Although it has been thought of as “socially facilitated nesting”
(Owens et al., 1982), it now appears that these groups of females aggregate for
nesting but disperse randomly during the internesting period. The turtles respond
independently to one or more proximal cues and commence a subsequent arribada
some 30 days later (Plotkin et al., 1995; 1997). Pritchard (1969) hypothesized that
ovulation and egg development would occur at approximately the same time for the
whole arribada cohort, and that females were retaining eggs until suitable emergence
cues arose. Although Lepidochelys spp. have internesting intervals significantly
longer than other species, ovulation still occurs within 2–3 days postoviposition
(Licht et al., 1982; Miller, 1997). Because arribadas are presumed to comprise
several smaller groups of turtles (Plotkin et al., 1995), perhaps prolonged renesting
intervals in arribada females acts to synchronize the final stages of egg development
in as many females as possible. In addition, arribadas may serve to delay oviposition
when conditions are unfavorable (Plotkin et al., 1997).
Although uncommon in other species, Limpus (1985) reports two instances of
prolonged oviducal egg retention (41 and 42 days) in female C. caretta with disabled
hind flippers. Dissection confirmed that in both cases the oviducal eggs were from
the most recent ovulation. Moreover, eggs from one of these females were buried
in an artificial nest and achieved emergence success of 76.2%, providing further
evidence to support Pritchard’s hypothesis that prolonged egg retention occurs to
allow a female to wait for suitable nesting cues.
5.5.9.2 Year-Round Nesting
Nesting seasons for most populations are constrained temporally. However, for most
species, uninterrupted year-round nesting has been recorded at some locations (Witzell, 1983; Marquez, 1994; Hirth, 1997; also see Miller, 1997), although in most of
these cases the majority of nesting activity occurred in a peak period spread over
several months. Bimodal nesting with small and large peak periods has been recorded
for at least one population of D. coriacea; however, relationships between these two
apparently separate cohorts are unknown (Chevalier et al., 1999). Unfortunately,
comprehensive data sets detailing year-round nesting are not available, and thus we
can only speculate reasons to support why and how they persist. Presumably, three
factors control nesting seasonality: (1) the ability to find a mate and successfully
copulate, (2) the suitability of a beach to successfully incubate sea turtle eggs, and
(3) the suitability of the beach to allow efficient offshore dispersal of the hatchlings.
1123 book.book Page 151 Thursday, November 14, 2002 11:50 AM