Here's the paper that the news articles reference (note: this was published back in December):
Philip M. Wilkinson, Thomas R. Rainwater, Allan R. Woodward, Erin H. Leone, and Cameron Carter
(2016) Determinate Growth and Reproductive Lifespan in the American Alligator (Alligator mississippiensis): Evidence from Long-term Recaptures. Copeia: December 2016, Vol. 104, No. 4, pp. 843-852.
The perception that crocodilians exhibit indeterminate growth is common
in the general reptilian literature. However, this assumption is
frequently based on observations of immature and young adult animals and
therefore lacks a complete understanding of adult growth patterns.
Long-term mark-recapture studies appear to be the most certain method of
determining growth patterns of adult crocodilians. From 1979–2015, we
conducted a mark-recapture study of an American Alligator (Alligator mississippiensis)
population on the Tom Yawkey Wildlife Center (YWC) in coastal South
Carolina to examine long-term growth patterns and the influence of age
on multiple reproductive parameters. We found no discernible linear
growth in 19 of 31 adult female and 7 of 19 adult male alligators over
periods of 5–33 years. The mean maximum reproductive lifespan for female
alligators on the study site was 46 years, and females continued to
reproduce for an extended period of time after reaching maximum size.
The Schnute growth model predicted that male alligators grew at a faster
rate and attained a greater estimated mean terminal snout–vent length
(SVL) than females (males = 186.9, CI0.95 = 184.5, 189.3 cm; females = 135.9, CI0.95
= 134.1, 137.8 cm) at the hypothetical age 75. In addition, the model
predicted that males exhibited a greater estimated mean size (SVL =
182.0, CI0.95 = 179.6, 184.4 cm) and age (43 years) at which growth essentially ceased when compared to females (SVL = 131.4, CI0.95
= 129.5, 133.2 cm; 31 years). However, actual growth records of
individual alligators suggested that the growth model may have
overestimated the age at which male alligator growth ceased. The
estimated mean earliest age at sexual maturity was 11.6 years (CI0.95 = 10.5, 12.8) for males and 15.8 years (CI0.95
= 14.5, 17.1) for females. We also documented that alligators on the
site commonly live to 50 and can possibly live to >70 years of age.
This study provides evidence that both male and female American
Alligators in a population in coastal South Carolina exhibit a pattern
of determinate growth and adds to a growing list of studies suggesting
crocodilians as a group exhibit this growth pattern rather than
indeterminate growth. Our findings are important for modeling population
growth and determining sustainable harvest rates, particularly for
alligators living near their northern distributional limit where growing
seasons may be shorter and onset of sexual maturity later than in more
southern portions of their range.
Alligator growth and reproduction -- new discoveries (with videos)