Long-Term Changes in a Population of Alligator mississippiensis in South Carolina

Abstract

The status of the American alligator in a man-made reservoir in South Carolina was deter- mined through the use of mark-recapture and mark-resighting techniques. Results were compared to studies conducted during the 1970s to determine changes in population size, population structure, and number of nests. Over the last 14 years the number of alligators in Par Pond has more than doubled (from an estimated 110 to 266), and the size structure of the population has shifted from one with a high proportion of large adults to one with a high proportion of juveniles (<1.8 m). The sex ratio of animals captured from 1986-1989 (2.6 male: 1 female) was similar to that found in the 1970s (3.2:1; Murphy, 1977). The number of nests and the number of successful nests was variable among years, ranging from no nests in 1986 to 8 nests in 1988 for an average of 4.0 nests per year, an increase from the 2.3 observed during the 1970s. Overall, the alligator population in Par Pond appears to be quite healthy, showing an overall average annual exponential rate of increase (r.p.a) of 6% and a juvenile r.p.a. of 10%. It is expected that the population will continue to increase in size, but that the average annual exponential rate of increase will decrease as the carrying capacity of Par Pond is reached.