Population Ecology A Stage-Based Population Model for American Alligators in Northern Latitudes KYLEE DUNHAM, Framingham State University, 100 State Street, Framingham, MA 01701, USA STEVE DINKELACKER, 1 Framingham State University, 100 State Street, Framingham, MA 01701, USA JEFF MILLER, Missoula College of the University of Montana, 909 South Avenue, Missoula, MT 59801, USA ABSTRACT Very little is known about the population dynamics of American alligators in northern latitudes. To better define the characteristics of the northern population, we combined published life-history and vital rate data for studies conducted in North Carolina and South Carolina; for comparison, we gleaned the same information from the literature for the southern (Florida and Louisiana) population. We constructed a 5- stage Lefkovitch matrix model for each population. The models showed that the southern population was stable and slightly increasing (l ¼ 1.02), whereas the northern population was in decline (l ¼ 0.870). We integrated potential impacts of climate change into the northern population model to determine how the population might respond to increased temperature and decreased precipitation. An increase in temperature would benefit the northern population; however, a decrease in precipitation or the combined effects of temperature increase and precipitation decrease would negatively affect the viability of the northern population. Two priorities result from modeling these scenarios: 1) a long-term monitoring program is needed to acquire the life-history and vital rate data on the northern population, and 2) current alligator habitat must be conserved or improved to insulate the species from potential drought associated with climate change. Ó 2014 The Wildlife Society. KEY WORDS alligator, climate, fecundity, growth, population, RAMAS, survival. The American alligator (Alligator mississippiensis) is found throughout most of the southeastern United States from Texas eastward to Florida and northward to North Carolina (Elsey and Woodward 2010); however, the majority of the research conducted has been on populations located in Florida and Louisiana, where populations are intensively managed and restoration projects are underway to protect habitat (Nichols et al. 1976, Abercrombie 1989, Woodward 1996, Mazzotti et al. 2009). Little is known about the population dynamics of alligators that inhabit the north- ernmost part of their range in Arkansas, North Carolina, and South Carolina. In these states, alligators are listed as threatened (North Carolina), or hunted as game species and also listed as either endangered (Arkansas) or moderate priority species in need of management (South Carolina; North Carolina Wildlife Resource Commission 2005; South Carolina Department of Natural Resources 2005, 2012; Arkansas State Game and Fish Commission 2014). Alligator populations are susceptible to changing environ- mental conditions (Mazzotti et al. 2009), especially temperature and precipitation. Temperature is the most important factor in determining the growth rate for American alligators (Lance 2003). At and below 168 C, alligators cease eating, and subsequently stop growing (Joanen and McNease 1989, Lance 2003). In North Carolina, air temperature remains below 168 C for roughly 6 months of the year (Lance 2003). As a result, growth rates of alligators are slower than those found in Florida and Louisiana. An alligator may require up to 18 years to reach the sexually mature size of 1.83 m in North Carolina (Nichols et al. 1976), in contrast, in Louisiana and Florida an alligator requires 10–12 years to reach the same size (i.e., size at sexual maturity; Abercrombie 1989, Lance 2003). Reproduction and survival are linked to precipitation because rainfall greatly influences the hydrologic conditions of the habitat (Mazzotti et al. 2009). Prolonged drought may decrease habitat area, which could force the majority of the population into smaller areas, therefore increasing competi- tion for food and access to water, and increasing cannibalism of smaller size classes (Deitz 1979, Hayes-Odum and Jones 1993, Mazzotti et al. 2009). During droughts, larger animals will typically defend the deeper water, and in the winter, smaller animals are forced into the shallow freezing water causing them to become ill or die (Hayes-Odum and Jones 1993). If drought were to affect the availability of food, then alligators are likely to decrease reproductive rates as well as growth rates (Mazzotti et al. 2009). Additionally, under drought conditions, females decrease nesting effort, there- fore reducing fecundity (Joanen and McNease 1989). Furthermore, a decrease in precipitation may cause salinity to increase. Both American alligator and American crocodile (Crocodylus acutus) hatchlings and juveniles lose body mass as salinity increases, even when food is readily available Received: 25 July 2013; Accepted: 23 January 2014 Published: 25 March 2014 1 E-mail: sdinkelacker@framingham.edu The Journal of Wildlife Management 78(3):440–447; 2014; DOI: 10.1002/jwmg.688 440 The Journal of Wildlife Management  78(3)