CONVENTION ON INTERNATIONAL TRADE IN ENDANGERED SPECIES
OF WILD FAUNA AND FLORA
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HAWKSBILL TURTLES IN THE CARIBBEAN REGION:
Basic Biological Characteristics and Population Status

Summary
A compendium of information on marine turtles around the world was published nearly two decades
ago, and subsequently reprinted with brief updates (Bjorndal, 1982, reprinted in 1995). More recently,
an anthology of review articles on The Biology of Sea Turtles was published (Lutz and Musick,
1997), followed by a manual expounding standardized techniques for research and management
(Eckert et al., 1999). There have also been compilations of information on the hawksbill (e.g., Carr et
al., 1966; Witzell, 1983; Eckert et al., 1999; Rhodin and Pritchard, 1999) as well as numerous
individual projects.
Hawksbill turtles are highly complex, specialized marine reptiles. To complete the life cycle they
require a diversity of environments, including terrestrial beaches, open ocean, coral reefs and coastal
waters. Many of the biological characteristics of hawksbills discussed in this review can be treated
together under a single concept: “late maturing and long-lived.” This incorporates considerations such
as: fecundity, survivorship and recruitment, age structure, growth rate, and age at maturity.
Typically, they have a very high fecundity, or reproductive output: an average of 140 eggs is laid in
one nest; several clutches are laid in one season; and nesting occurs during multiple seasons, although
rarely annually. The high fecundity is offset by high mortality during early phases of the life cycle
with probably less than one out of 1000 eggs surviving to adulthood. There are few studies of age
structure, recruitment or survivorship at different life phases, but once a turtle reaches large size, and
maturity, survival rate is potentially high, about 95% annually for some nesting females. Sex ratios are
poorly understood, but they seem to be biased toward females.
Hawksbill turtle populations have numerous year-classes in a single population, with a relatively large
numbers of immatures and relatively small numbers of adults. Several population models of marine
turtles, including hawksbills, have shown that the large immatures and adults are especia lly important
to the maintenance of a stable population (Crouse, 1999). This characteristic is shared with other late
maturing and long-lived species, which as a rule are especially vulnerable to mortality, including
exploitation, concentrated on large immatures and adults (Musick, 2001).
Linear growth rates vary between size classes and localities, but are slow enough to indicate that
hawksbills take more than a decade to mature: the time from egg until returning to the same beach to
breed for the first time may require between 15 and 40 years. However, there are considerable
differences in growth rate between different areas, with fast growth (e.g. in Cuba and Mexico)
influencing the age at which sexual maturity is reached, and also the intrinsic rates of increase and
recovery times for depleted populations. Available evidence demonstrates that age of sexual maturity
in hawksbills can extend beyond a single decade and possibly more than two.