PREVALENCE AND DETAILS OF POLYDACTYLISM IN THE AMERICAN ALLIGATOR, ALLIGATOR MISSISSIPPIENSIS, IN LOUISIANA, USA

Polydactylism has been described in the American Alligator (Alligator mississippiensis) and other crocodilians, but to our knowledge the prevalence of this limb abnormality has not been examined in detail. As part of a head start program in which juvenile alligators are released back to the wild after being hatched from eggs collected in the wild, in 2016 we examined 58,106 alligators for this condition. Polydactylism occurred in 106 alligators (0.18%). Front limbs and limbs on the right side were more commonly affected than rear limbs or those on the left side (n = 77 right front and n = 59 left front; n = 34 right rear and n = 20 left rear). Of the 106 alligators with polydactylism, extra toes were present on one limb in 46 cases (43.40%), on two limbs in 42 instances (39.62%), on three limbs in 12 alligators (11.32%) and six alligators had extra toes on all four limbs (5.66%). Analyses of patterns of polydactylism could not support hypotheses that polydactylism was more common on any combination of position (front, back, left, right) based on number of limbs affected. Alligators typically have 18 toes; the mean number of toes present in this series of polydactylism was 22.5 +/- (SD) 2.8 toes (range 19-32). One alligator had eight toes on each limb, for a total of 32 toes present (14 more than normal). Several other cases of polydactylism were noted in review of anecdotal observations recorded from farm releases made in prior years, from hatchlings obtained from eggs collected and incubated at Rockefeller Wildlife Refuge in Grand Chenier, Louisiana, or from wild harvested alligators taken in statewide sanctioned harvests.