Long-term trends in marine turtle size at maturity at an important Atlantic rookery

For species reaching maturity at a range of ages or sizes, factors that
influence juvenile growth and size at maturity may have lasting impacts on
overall fitness. Assessing when animals reach maturity is especially
challenging for species which are difficult to follow through time as a
result of highly migratory behavior, long life spans, or both. We examined
nesting female size in a reproductive assemblage of green turtles
(Chelonia mydas) and loggerheads (Caretta caretta) on the east coast of
Florida, USA. We used a long-term dataset from 1982-2019 to estimate a
minimum size at maturity interval on the basis of two standard deviations
below mean female size for each species. The minimum size intervals for
green turtles (81.4 - 89.3 cm) and loggerheads (68.1 - 79.1 cm) were lower
than most previous estimates in the literature, many of which were simply
the smallest individual ever observed. There was a significant decrease in
the upper bound of the minimum size interval over the study period for
both green turtles (1.6 cm) and loggerheads (4.1 cm). These shifts in size
at maturity may be the result of changes in population demographics,
habitat quality, and behavioral reactions to these changes. The
development and periodic reassessment of robust estimators of maturity are
an important part of programs centered around the monitoring and
conservation of vulnerable wildlife populations.