Data from: Life histories and conservation of long-lived reptiles, an illustration with the American Crocodile (Crocodylus acutus)

1. Successful species conservation is dependent on adequate estimates of
population dynamics, but age-specific demographics are generally lacking
for long-lived iteroparous species. Accurate demographic information
allows estimation of population growth rate, as well as projection of
future population sizes and quantitative analyses of fitness trade-offs
involved in evolution of life-history strategies. 2. Here, a long-term
capture-recapture study was conducted from 1978-2014 on the American
crocodile (Crocodylus acutus) in southern Florida. Over the study period,
7,427 hatchlings were marked and 380 individuals were recaptured for as
many as 25 years. We estimated survival to be strongly age-dependent with
hatchlings having the lowest survival rates (16%) but increasing to nearly
90% at adulthood based on mark-recapture models. More than 5% of the
female population were predicted to be reproductive by age 8 years; the
age-specific proportion of reproductive females steadily increased until
age 18 when more than 95% of females were predicted to be reproductive.
Population growth rate, estimated from a Leslie-Lefkovich stage-class
model, showed a positive annual growth rate of 4% over the study period.
3. Using a sensitivity analysis, we revealed that the adult stage, as
expected was the most critical stage for population growth rate; however,
the survival of younger crocodiles before they became reproductive, also
had a surprisingly high elasticity. We found that variation in
age-specific fecundity has very limited impact population growth rate in
American crocodiles. 4. We used a comparative approach to show that the
original life history strategy of American crocodiles is actually shared
by other large, long-lived reptiles: while adult survival rates always
have a large impact on population growth, this decreases with declining
growth rates, in favor of a higher elasticity of the juvenile stage. 5.
Crocodiles, as a large, long-lived and highly fecund species deviate from
the usual association of life-histories of “slow” species. Current
management practices are focused on nests and hatchling survival; however,
protection efforts that extend to juvenile crocodiles would be most
effective for conservation of the species, especially in an
ever-developing landscape.