- Link:
- http://hdl.handle.net/1860/2523
- Collection:
-
- Subjects
- Life sciences Leatherback turtle--Eggs--Incubation Leatherback turtle--Fertility
- Creator:
- Tomillo, Maria del Pilar Santidrián
- Language
- en_US
- Type
- Thesis
- Description
- The leatherback turtle (Dermochelys coriacea) is
critically endangered. The population of leatherbacks that nest at
Parque Nacional Marino Las Baulas, in Costa Rica declined by 95% in
less than 20 years. Annual mortality rate of adults was higher than
expected in a natural population and mortality rates of juveniles
could double those of a stable population. Conservation efforts
since the Park was established in 1991 resulted in higher
production of hatchlings per egg laid. However, the overall
hatchling output decreased because of the decreasing number of
nesting turtles. Simulations on the effect of egg poaching showed
that poaching was the most important cause of population decline at
Las Baulas. Heavy poaching resulted in a stepwise decline in number
of nesting turtles due to consecutive reductions in each nesting
stage. The nesting population declined faster and was extirpated
sooner with 90% egg poaching than with 20% adult mortality.
However, both protection in the ocean from fishing and on the beach
are critical to the survival of the population. Behavior of
hatchling leatherback turtles on the walk to the water was driven
by predation risk. Hatchling leatherback turtles decreased
predation risk emerging in groups and dispersing. Straightness of
tracks increased during the process of departure and was lower in
areas of higher exposure to light pollution. Nest success of
leatherback turtles was driven by environmental variability. High
temperatures in the nest reduced its success, and high rainfall and
low ambient temperatures resulted in higher production of
hatchlings. Predicted emergence success was related to El Niño
Southern Oscillation (ENSO). Leatherback female turtles increased
reproductive success over time by increasing number of eggs, number
of clutches and arriving earlier in the season, when hatchling
production was greater. In conclusion, the population decline at
Las Baulas was mainly caused by egg poaching but is still
threatened by high mortality in the ocean. Conservation efforts
have been efficient at increasing hatchling production. However,
the stochastic nature of nest success and consequently, recruitment
rate, may increase the risk of extinction of a population already
reduced from past poaching and fisheries.
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