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Intensive beach management as an improved sea turtle conservation strategy in Mexico

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We evaluate the role of intensive beach management, meaning intense patrolling and nest reburial to a central hatchery, as a strategy for improving the success of sea turtle conservation at nesting sites in Mexico. We report the results of an experimental program at Playa Cuixmala, Jalisco, western Mexico. Sea turtle conservation efforts in Mexico have, in general, poor results because of lack of funds, which leads to insufficient beach protection and severe negative effects of nest removal on hatching success and sex ratios. Alternative strategies are needed to optimize limited resources. We predicted that intensive beach management, which included intense patrolling and careful nest reburial, could be an effective way to maximize nest survival and hatchling release under limited financial and human resources. The results of our 9-year study were very positive. Survival rate increased several fold during the study period. Hatching success and sex ratios were not significantly different between in-situ and removed nests. Survival in removed nests was, however, much higher that in-situ nests, because of predation and beach erosion. In total, the small (3 km length) Playa Cuixmala became the second most productive sea turtle nesting beach in the region because of these concentrated efforts. Intense beach management can be an important technique for sea turtle conservation, and can be properly applied to small beaches or the most productive sections of large beaches.
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Intensive beach management as an improved sea turtle
conservation strategy in Mexico
Andre
´s Garcı
´a
a,1
, Gerardo Ceballos
a,b,
*, Ricardo Adaya
a,b
a
Fundacio
´n Ecolo
´gica de Cuixmala A.C., Aartado Postal 161, San Patricio, Melaque 48980, Jalisco, Mexico
b
Instituto de Ecologı
´a, UNAM, CU, Apartado Postal 70-275, Me
´xico DF 04510, Mexico
Received 7 December 2000; received in revised form 12 September 2002; accepted 24 September 2002
Abstract
We evaluate the role of intensive beach management, meaning intense patrolling and nest reburial to a central hatchery, as a
strategy for improving the success of sea turtle conservation at nesting sites in Mexico. We report the results of an experimental
program at Playa Cuixmala, Jalisco, western Mexico. Sea turtle conservation efforts in Mexico have, in general, poor results
because of lack of funds, which leads to insufficient beach protection and severe negative effects of nest removal on hatching success
and sex ratios. Alternative strategies are needed to optimize limited resources. We predicted that intensive beach management,
which included intense patrolling and careful nest reburial, could be an effective way to maximize nest survival and hatchling release
under limited financial and human resources. The results of our 9-year study were very positive. Survival rate increased several fold
during the study period. Hatching success and sex ratios were not significantly different between in-situ and removed nests. Survival
in removed nests was, however, much higher that in-situ nests, because of predation and beach erosion. In total, the small (3 km
length) Playa Cuixmala became the second most productive sea turtle nesting beach in the region because of these concentrated
efforts. Intense beach management can be an important technique for sea turtle conservation, and can be properly applied to small
beaches or the most productive sections of large beaches.
#2003 Elsevier Science Ltd. All rights reserved.
Keywords: Beach management for sea turtles; Beach protection; Sea turtles; Nest translocation; Lepidochelys olivacea; Nest predation; Beach erosion;
Conservation strategy; Enclosed hatchery; Sex–temperature determination
Debate over the optimum methods for conserving
dwindling populations of endangered sea turtles has
been a concern of the conservation community for dec-
ades. Conservation of sea turtles include management
of nesting beaches, nest translocation to protected
hatcheries, head starting, reduction or elimination of
natural predators, and protection against poaching and
fishing (Bjorndal, 1995; Ehrenfeld, 1995). The protec-
tion of nesting beaches and nests is considered part of a
broader sea turtle conservation strategy, where mortality
factors at other stages of the life cycle have to be
addressed (Frazer, 1992; Spotila et al., 2000).
The protection of nesting beaches and the nest trans-
location to enclosed hatcheries has been widely imple-
mented (INP, 1990; Pritchard et al., 1993; Cornelius,
1995; Chan and Liew, 1995; Pritchard, 1995; Tow and
Moll, 1995). Nest translocation is an important con-
servation tool on beaches where natural hatching is low
or non-existent due to poaching, predation, or erosion.
There is controversy, however, about the utility of nest
translocation and nest removal to hatcheries versus in-
situ protection because managed nests may experience
lower hatching success and altered sex ratios (Limpus et
al., 1979; Mrosovsky and Yntema, 1980; Parmenter,
1980; Blanck and Sawyer, 1981; Morreale et al., 1982;
Dutton et al., 1985; Eckert and Eckert, 1990; Ma
´rquez,
1990; Cornelius et al., 1991; Pritchard et al., 1993;
Bjorndal, 1995; Chan and Liew, 1995; Ehrenfeld, 1995;
Pritchard, 1995).
The main strategies for sea turtle conservation in
Mexico includes a complete ban on exploitation of sea
0006-3207/03/$ - see front matter #2003 Elsevier Science Ltd. All rights reserved.
PII: S0006-3207(02)00300-2
Biological Conservation 111 (2003) 253–261
www.elsevier.com/locate/biocon
* Correspondingauthor. Tel.: +52-5-622-9004; fax: +52-5-622-9004.
E-mail addresses: chanoc@unm.edu (A. Garci
´a), gceballo@mir-
anda.ecologia.unam.mx (G. Ceballos), raal@coatepec.uaemex.mx
(R. Adaya).
1
Present address: Department of Biology, Museum of South-
western Biology, University of New Mexico, Albuquerque, NM
87131, USA.
turtles and their eggs, and the protection of nesting
beaches (SEPESCA, 1991). Management has mainly
focused on nest protection in centralized beach hatch-
eries (Kilma and McVey, 1995; INP, 1990; SEPESCA,
1990b). Recurrent problems related to lack of funds
include insufficient beach protection and inadequate
management of nest removal to hatcheries have resulted
in poor overall success of the conservation programs
(SEMARNAT, 1996; Pritchard, 1995).
The objective of this study was to evaluate the poten-
tial of intensive beach management as an improved
strategy for sea turtle conservation in Mexico. By
intensive beach management we mean both intensive
beach patrolling and adequate nest reburial, to avoid
both natural and human-induced nests losses, and
negative effects of nest management on sex ratios and
hatching success. To carry out this study we selected
Playa Cuixmala, a small beach ( <3 km length) in the
Jalisco coast, western Mexico. We report here the
results of nine annual breeding seasons of Olive ridley
(Lepidochelys olivacea).
In our work we test the following postulates:
1. Concentrating on intensive beach management is
an efficient conservation strategy to maximize
nest protection under limited financial and
human resources.
2. Natural and human-caused nest losses can be
effectively reduced by nest removal to an
enclosed hatchery.
3. Careful management of nest removal and hatch-
eries minimizes their negative effects on hatching
success and sex ratios.
1. Study site
Playa Cuixmala (19220–19210lat N and 105000
104590long W) is located along the southern coast of
Jalisco, 140 km south of Puerto Vallarta, and is part of
the Chamela-Cuixmala Biosphere Reserve (Ceballos
and Garcia, 1995). It is 3 km long, with marked
monthly variations in width (30 to 70 m), especially
during the rainy season. The physical and biotic char-
acteristics of the area are described elsewhere (Bullock,
1986; Garcı
´a and Ceballos, 1994). The climate is tropi-
cal, hot, humid, and characterized by well-defined dry
and rainy seasons. Annual mean temperature is 24.9 C
and mean annual rainfall is 788 mm, concentrated
between July to October; the dry season can last 8
months, from November to June (Bullock, 1986).
Human activities have profoundly impacted sea turtle
populations along the Jalisco coast. Large ‘‘arribadas’’,
including groups from 20,000 to 30,000 of Lepidochely
olivacea females, were recorded on Mismaloya Beach (70
km north of Cuixmala) as late as 1970 (Casas-Andreu,
1978; Cliffton et al., 1995; SEPESCA, 1990a). Playa
Cuixmala has been officially protected as a sea turtle
nesting sanctuary by a presidential decree since 1986
(SEPESCA, 1986). Prior to 1988, poaching was a com-
mon activity. Beach area is highly variable, with beach
erosion caused by high tides during hurricanes and tro-
pical storms (from July to October), when beach area
can be reduced up to 70% in a single storm (e.g. Sep-
tember 1987). Nest loss by beach erosion is high because
the hurricane season coincides with the sea turtle nest-
ing season (Casas-Andreu, 1978; Bullock, 1986).
2. Methods
Data for this study were collected from July 1988 to
March 1997, comprising nine annual breeding seasons
(July–March). All the activities were carried out by the
staff of the Cuixmala Ecological Foundation, an organ-
ization responsible for the protection of Cuixmala
beach. Before the breeding season started, guards were
trained and the hatchery built. The beach was protected
against human poaching by controlling its two points of
accesses. Beach patrols were conducted at 3-h intervals
from 22:00 to 07:00 to find tracks of nesting females
that lead to the nests, or to locate the nesting females.
Due to regular patrols, the small beach length, and the
ability to rapidly transport the removed nests to the
hatchery, time between oviposition and reburial was no
longer than 3 h.
After nests were found, they were collected, num-
bered, clutch size recorded, and transported in clean
plastic bags to the enclosed hatchery by foot. The
enclosed hatchery was located in a well-drained area
free of vegetation and shades. The hatchery was moved
each year around the area to avoid accumulation of
bacteria and other kinds of contamination. The
enclosed hatchery was 10 35 m and was constructed
of 2.5-m high wooden posts, and woven wire mesh, as
well as a 1.5-m high mosquito mesh. The wooden posts
and the woven and mosquito mesh were buried 0.5 m to
avoid predators such crabs and coatis.
In order to control hatchlings emergence, mosquito
mesh tubes were placed around each nest close to
hatching. Hatchlings were counted and released imme-
diately to the sea by putting them on the beach to allow
them to move along the sand. Two days after the nat-
ural emergence of hatchlings, nests were completely
opened to count the hatched, non-hatched, and infected
eggs, and the dead and live hatchlings inside the nest.
We evaluated human poaching by counting the num-
ber of poached nests compared to all of the nests recor-
ded in the beach. To evaluate the importance of the
intensive protection of our small beach we compared
our data with information from all protected beaches
along the Jalisco coast (SEPESCA, 1992, 1993;
254 A. Garci´a et al. / Biological Conservation 111 (2003) 253–261
SEMARNAP, 1996). For comparisons between beaches,
results were standardized by calculating the average
number of nests protected per linear kilometer, due to
variability in beach length. An index of relative importance
of beaches in relation to nest protection was determined by
dividing the number of nests protected by the linear
kilometers of each beach. For the purpose of comparison,
nest data was presented by calendar year instead of
breeding season, in accordance with government
reporting procedures for the other beaches.
We experimentally evaluated the natural causes of
nest loss by comparing survival of translocated (i.e.
hatchery) and in-situ nests. Experiments were per-
formed in August 1990, July 1991, and October 1994.
The removed nests were carried to a hatchery as descri-
bed above, and the in-situ nests were left exposed to
beach erosion and predation. Nests found in the field
were alternately allocated to each condition. At the end of
each experiment we recorded the number of surviving and
destroyed (i.e. nests lost to predation or beach erosion)
nests. The number of nests allocated to hatchery and in-
situ conditions in the experiments were 32 in 1990, 80 in
1991, and 18 in 1994. In all experiments, we evaluated
the effect of nest removal to the enclosed hatchery on
hatching success. Hatching success was calculated by
dividing the number of hatched eggs by the total number
of eggs found in each nest.
We compared nestling sex ratios from removed versus
in-situ nests in the 1994 experiment. In Lepidochelys
olivacea, sex ratios are female and male biased at tem-
peratures between 32 and 34 C and between 26 and
28 C, respectively. The threshold temperature, where a
balanced sex ratio is produced is around 30 C(McCoy
et al., 1983). We monitored the temperature inside all
nests during the incubation period twice a day (06:00
and 14:00 h), to determine if incubation temperatures
differed in the removed and in-situ nests. Thermo-
couples (Bailey Instruments, model BAT-12, with 0.1 C
of resolution) were used to monitor nests’ temperature
(see Benabib, 1984; Mrosovsky, 1995). Based on the
recorded temperature profiles, we predicted expected sex
ratios. Twenty hatchlings from each nest were selected
randomly for sex determination in the laboratory using
the techniques of Humanson (1979) and Merchant-Lar-
ios et al. (1989). Sample size was 20 turtles from each
nest, and was similar to, or larger than, sample sizes in
other field studies on temperature–sex determination
(Benabib, 1984, Mrosovsky et al., 1984). The sex of 283
and 247 turtles from 17 transplanted and 14 in-situ nests
was determined.
3. Results
Our study comprised 72 months of fieldwork and
8640 daily beach surveys, and represents the longest
study of Lepidochelys olivacea nesting in Mexico. Alto-
gether, there were 2418 nests protected and 141,548
hatchlings released in Cuixmala from July 1988 to
March 1997. The frequency of laid nests during the
breeding season (July–March) showed a peak (73%
from total recorded nests) from August to October
(Fig. 1). Mean number of nests laid per month in the 3
km study site for the 72 months was 33.3 (S.D.=36.9),
with the highest and lowest values in September
(mean=81, S.D.=40) and March (mean=2, S.D.=2),
respectively.
3.1. Intensive beach management
How efficient were our efforts to reduce natural and
human-induced mortality of nesting sea turtles and
nests at Cuixmala beach? Not surprisingly, intense
beach management, which included patrolling and nest
reburial, was an effective way to reduce nests losses in
Cuixmala. Altogether, the outcome of such efforts was
the release of 141,548 hatchlings. The number of pro-
tected nests showed an impressive recovery from 20
nests in 1989 to 456 in 1996, with an annual average of
300 (S.D.=127 nests) and a total of 2418 nests (Fig. 2).
The effectiveness of our program was the combined
reduction of mortality caused by poaching and natural
factors such as the destruction of nests by beach erosion
and predators. Poaching was completely halted. During
the 1987–1988 and 1988–1989 breeding seasons when
Cuixmala beach was not strictly protected, most nests
(>90%) were poached. In contrast, during the following
8 years, when beach protection was enforced, only two
nests were poached in 1990.
Our work also eliminated nest losses by predation or
beach erosion among the nests in the hatchery. In con-
trast, only an average 56% (range 44–70%) of the in-
situ nests survived because of beach erosion and preda-
tion by coatis (Nasua narica;Fig. 3). Nest survival in the
hatchery was statistically higher than in-situ nests
(T=5.02, df=4, P<0.05). If no management had been
done from 1989 to 1997, the total number of surviving
nests in Cuixmala could have been 1450 as a maximum,
when considering no poaching and a 56% average nest
survival rate. Adding the effects of poaching and natural
causes of nest destruction, it is likely that only 213 nests
(10%) and 14,155 hatchlings would have survived dur-
ing the study period.
3.2. Effects of nest translocation
An important part of the success of our program was
the translocation of nest to a hatchery to avoid nests
losses by beach erosion and predation. Our results
clearly indicate that our nest reburial technique had few
negative effects on hatching success and sex ratios
(Figs. 3 and 4). Hatching success was, on average,
A. Garci´a et al. / Biological Conservation 111 (2003) 253–261 255
higher in the in-situ (66%) than in hatchery (59%) nests,
but this difference was not statistically significant
(T=1.75, df=211, P>0.05). Hatching success varied
among experiments, and was higher in the in-situ nests
in 1991 and 1994, but lower in 1990. In the 1991
experiment, differences between in-situ and translocated
nest were statistically significant (T=3.53, df=137,
P<0.05), but in the 1990 and 1994 experiments, no sig-
nificant differences were found (T=1.14, df=46, P
>0.05 and T=1.48, df=24, P>0.05, respectively).
The hatchery and in-situ nests experienced similar
temperatures during the three week sensitive tempera-
ture period for sex determination (T=0.9, df=30,
P>0.05). The average temperature for such period was
Fig. 2. Recorded nests (bars) and released hatchlings (line) of Olive ridleys (Lepidochelys olivacea) at Cuixmala beach, Jalisco, Mexico, from 1988 to
1997.
Fig. 1. Annual nesting pattern of Olive ridleys (Lepidochelys olivacea) at Cuixmala beach, Jalisco, Mexico, from 1988 to 1997. A total of 2418 nests
were counted, averaging 33.3 (S.D. 36.9) nests per month.
256 A. Garci´a et al. / Biological Conservation 111 (2003) 253–261
30.5 C(N=266, S.D.=0.62) for in-situ nests and
30.6 C for hatchery nets (N=380, S.D.=0.62). Based
on observed temperatures, we expected slightly female
biased sex ratios in both conditions. Our results sup-
ported our predictions, because sex ratios did not differ
statistically between translocated and in-situ nests
(t=0.74, d.f.0 29, P>0.05), and were skewed towards
females (Table 1).
3.3. Comparison of Cuixmala and other regional
beaches
How do our results compare with other protected sea
turtle nesting beaches in the same region? Although we
hypothesized that intensive protection of a small beach
like Cuixmala could have a positive regional contri-
bution to sea turtle conservation, we did not expect the
Fig. 3. Percent of survival in in-situ (open bars) and removed (black bars) nests at Cuixmala beach, in 1990, 1991, and 1994.
Fig. 4. Hatchling success in-situ (open bars) and removed (black bars) at Cuixmala beach in 1990, 1991, and 1994.
A. Garci´a et al. / Biological Conservation 111 (2003) 253–261 257
magnitude of our results. The productivity of beaches
increased throughout the region during this study as a
result of sea turtle conservation efforts (Figs. 5 and 6).
Nonetheless, the relative contribution of the 3 km
Cuixmala beach to the total 50 km of protected beaches
along the Jalisco coast increased from 1989 to 1994. The
proportion of all successful nests increased from 4 to
16% while the proportion of all hatchlings released
increased from 3 to 18% of the regional totals (Fig. 5).
During that period, Cuixmala became the most impor-
tant beach for sea turtle conservation at the state level in
relative terms (i.e. number of hatchling released per km
of beach) and the second one in absolute terms (i.e. total
number of hatchling released).
4. Discussion
The general conservation lessons from our work on
sea turtle conservation are related to three issues. (1) We
explored the role of what we called intensive beach
management for sea turtle conservation. (2) We did this
because of a need to reduce both human-induced and
natural factors causing nest losses and hatching success.
(3) Through our work we tested the usefulness of nest
reburial to an enclosed hatchery as a conservation
strategy. It is important to emphasize, however, that our
data is based on a single beach.
A successful sea turtle conservation strategy in the
Pacific coast of Mexico must combine mechanisms to
reduce human-induced and natural factors causing nests
and hatchling losses. We believe that an intensive beach
management strategy like the one used in Cuixmala, can
be applied to practically any beach, modifying it
according to the local conditions, where human-induced
and natural factors causing nest and hatchling losses
may vary. Our results clearly indicated that intensive
beach management was a successful strategy to increase
the impact of our sea turtle conservation efforts.
Fig. 5. Total number of nests and hatchlings released on the Jalisco coast (open part of bars) and the relative contribution of Playa Cuixmala
(shaded part of bars; valves on top of the bars) from 1988 to 1995.
Table 1
Incubation temperatures and sex ratios in experimental conditions
for in-situ and removed nests at Cuixmala beach. Temperatures
standard deviation
Hatchery In situ
Mean temperature at incubation period 30.9 C1.169 30.4 C0.989
Mean temperature at sensitive period 30.6 C0.699 30.5 C0.761
Sex ratio 1:1.41 1:1.35
258 A. Garci´a et al. / Biological Conservation 111 (2003) 253–261
4.1. Human-induced nests losses
The strict control and patrolling of access to Cuix-
mala beach together with the constant beach patrolling
by the staff of the biosphere reserve, practically elimi-
nated both nest and sea turtle poaching. Our results
reinforce current views that beach protection is a prior-
ity strategy for sea turtle conservation (Alvarado and
Figueroa, 1992; Ratnaswamy and Warren, 1998; Wang
and Cheng, 1999).
The effects of poaching can be devastating for sea
turtles. Nest poaching has been the main mortality fac-
tor for sea turtle populations elsewhere along the Jalisco
coast where from 75 to almost 100% of all nests are
destroyed in some beaches. People poach turtle nests to
get eggs, which are illegally sold for human consump-
tion in local communities. Two examples illustrate the
severity of this problem; in Teopa beach (5 km length),
located immediately to the north of Cuixmala beach, an
average 80% of all nests were poached annually from
1989 to 1994. Similarly, in the 30-km total length of
Mismaloya and La Gloria beaches (with the highest
nesting activity in the region), 93% of the nests were
poached during the 1991 nesting season (SEPESCA,
1992). Despite the fact that Cuixmala beach is the
smallest protected beach in the Jalisco coast, it has
become one of the most productive beaches in that state
(SEPESCA, 1991, 1992; SEMARNAP, 1996).
In Mexico, beach patrolling has been focused on
relatively large beaches with high nesting activity.
However, the lack of adequate funding and the size of
the beaches have precluded the effectiveness of the con-
servation programs. Focusing protection and patrolling
on small beaches and the most productive portions of
large beaches is an important strategy that can be imple-
mented under limited resources to maximize conservation
impact.
4.2. Natural-induced nests losses
Our fieldwork positively indicated that beach erosion
and predation were natural causes of severe nest and sea
turtle hatchling losses. We used nest reburial to an
enclosed hatchery to reduce nests losses. The validity of
nest reburial to an enclosed hatchery as a tool for sea
turtle conservation has been questioned because in some
circumstances it reduces hatchling success and alters sex
ratios (Mrosovsky and Yntema, 1980, Morreale et al.,
1982, Mrosovsky, 1995). Sea turtle hatching success can
be affected by direct and indirect disturbance from
humans, climatic conditions, environmental unpredict-
ability (e.g. storms, floods, erosion), fungal and bacterial
Fig. 6. Relative importance (N/km) of the sea turtle conservation program of Playa Cuixmala in comparison with other protected beaches in the
Jalisco coast from 1991, 1992 and 1993.
A. Garci´a et al. / Biological Conservation 111 (2003) 253–261 259
diseases, and predation (Eckert and Eckert, 1990;
Bjorndal, 1995).
Nest reburial to an enclosed hatchery should be used
in beaches were natural causes of nest losses are com-
mon (Parmenter, 1980; Ehrenfeld, 1995; Grand and
Beissinger, 1997). Beach erosion, common at our site, is
also a common cause of nest losses in other sites. For
example, it has destroyed up to 30% of the nests in
Playa Nancite and Ostional, Costa Rica (Cornelius,
1986; Cornelius et al., 1991), and 60% of Dermochelys
coriacea nests in the Virgin Islands (Eckert, 1987; Eckert
and Eckert, 1990). Nest losses by predation were also
common in our study. Predation is also a major cause of
sea turtle nests losses in many beaches (Fowler, 1979;
Cornelius, 1986; Ma
´rquez, 1990; Cornelius et al., 1991;
Stancyk, 1995). Our results indicated that the risk of nest
losses by environmental factors outweighed any possible
disadvantages that might be caused by nest translocation.
Our study is the first in Mexico to evaluate the effect
of nest removal to an enclosed hatchery on sex ratios
under natural conditions. Sex determination in sea tur-
tles is temperature-dependent; cold incubation tem-
peratures tend to produce males while warm
temperatures tend to produce females (Bull and Vogt,
1979; Bull, 1980; Mrosovsky and Yntema, 1980; Vogt
and Bull, 1982; McCoy et al., 1983; Standora and
Spotila, 1985; Mrosovsky, 1995). In general, nest
removal has resulted in altered sex ratios because the
nests are incubated in either Styrofoam boxes or in sha-
ded enclosed hatcheries, drastically changing the humidity
and temperature of the incubation period (Morreale et al.,
1982; Mrosovsky, 1995). Under such conditions, sex
ratios produced are male biased, which can have profound
effects on the population dynamics and long-term con-
servation of the species (Morreale et al., 1982; Dutton et
al., 1985; Mrosovsky, 1995). Our results indicate that of
an enclosed hatchery, maintaining environmental condi-
tions as close as possible to the adjacent beach can mini-
mize negative effects on sex ratios.
5. Conclusions
The long-term conservation of endangered sea turtles
in Mexico, as in other regions of the world, depends on
their protection at nesting sites and other stages of the
life cycle. The evaluation of different conservation stra-
tegies at nesting sites is required to promote adequate
allocation of financial resources to improve conservation
impact. We propose that intensive beach management is
a valuable conservation strategy of sea turtle nesting
beaches, aimed to reduce both human and natural
induced nests losses. Intensive beach management offers
hopes for sea turtle conservation in countries like Mex-
ico, and improves our chances to reduce sea turtle
extinction probabilities worldwide.
Acknowledgements
Funding and logistic support for this study was kindly
provided by the Cuixmala Ecological Foundation. We
dedicate this paper with our deepest gratitude to Sir James
Goldsmith who made the protection of Cuixmala beach
possible. Several members of the Cuixmala Foundation
have been very important in the implementation of the sea
turtle conservation program; in particular we are grateful
to Alix Goldsmith, Efre
´n Campos, Luis de Rivera, Gof-
fredo Marcaccini, Cristina Olivier, Adrian Pin
˜a, Gabriel
Barrera, and Bonifacio Alvarado. The rangers of the
Chamela-Cuixmala biosphere reserve were invaluable for
our sea turtle conservation activities. The Instituto de
Ecologı
´a, UNAM, has provided continuous support to G.
Ceballos. Horacio Merchant kindly helped us with the
technique for sexing sea turtles, and the Universidad
Auto
´noma del Estado de Mexico provided logistic facil-
ities for processing some of the samples. We would like to
thank our colleagues and friends Humberto Berlanga,
Alejandro Pen
˜a, Alejandro Espinoza, Raul Martı
´nez,
Sergio Lo
´pez, Marciano Valtierra, David Valenzuela, and
Cuauhte
´moc Cha
´vez, for their help during field work and
data analysis at different times during the study. Vincent
Burke, Rodrigo Medellı
´n, Noel Snyder, Norman Scott
Jr., Mark Schwartz, H.G. Davis, and two anonymous
reviewers kindly read earlier versions of the manuscript
and made suggestions that improved it considerably.
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Sandy Point, St. Croix, US Virgin Islands, is a high-energy beach characterized by deep, unobstructed access. Gravid leatherbacks deposit as many as 10 clutches (mean 4.9) annually and exhibit a high degree of nest dispersal along the length and width of the beach. Short-term erosion and accretion cycles result in the annual loss of 45-60% of nests laid. The zones of greatest instability vary from year to year. Wide nest dispersal may reduce the prospect that a high proportion of reproductive effort will be lost with the destruction of any particular zone of habitat. Nest dispersal should occur whenever nest survival is not strongly correlated with available environmental information. -from Author