Effects of Egg Mass, Hatchling Size and Clutch on Growth of Female American Alligators ( Alligator mississippiensis )

Growth of young American alligators ( Alligator mississippiensis; N = 119 total animals) was measured for five clutches (N = 4‐11 animals per clutch) for each of three distinct years (hatched summer 2017, 2018, or 2019). We measured egg mass within two weeks of oviposition, and all eggs were artificially incubated in the lab at 30°C and 85‐95% relative humidity, which produced only female alligators. Eggs were individually numbered and labeled, and clutch identity was determined on initial collection from wild nests. Egg survival was >96%. Hatchling wet body mass, snout‐to‐vent length (SVL) and head length (HL) were measured within 4 days of hatching, prior to yolk absorption and first feeding. Upon hatching, alligators’ dorsal sides were photographed for identification of each hatchling's unique markings, which allowed for matching each individual animal's egg and hatching data with subsequent growth. We measured wet body mass, SVL and HL every 2 weeks for ~150 days (5 months) for each animal. Within each year, animals were group housed under identical thermal conditions (27‐30°C) and fed a matching ad libitum diet of 56% protein alligator food (LoneStar, Nacogdoches, TX). Analyses indicate that egg mass and initial hatchling size, and not clutch, are the most important factors determining growth in young alligators.