Observations of a Small Population 



of Estuarine-Inhabiting Alligators 



Near Southport, North Carolina 



William S. Birkhead 



Division of Science and Mathematics, 



Columbus College, Columbus, Georgia 31993 



AND 



Charles R. Bennett 



National Marine Fisheries Service, 

 Environmental Assessment Branch, Portland, Oregon 97208 



ABSTRACT. — Field observations of the American Alligator, Alliga- 

 tor mississippiensis, were made incidental to a five-year study of the 

 nursery use of Dutchman Creek estuary near Southport, North Carol- 

 ina, by estuarine dependent fishes and shell fishes. Alligators were 

 most frequently seen between April and July and occurred over a wide 

 range of salinities. Some individuals that inhabited the lower reaches 

 of the estuary appeared to have shifted their distribution in response to 

 a major alteration of this habitat. After the headwaters and principal 

 tributaries of Dutchman Creek were bisected by the discharge canal of 

 a nuclear power plant, alligators appeared to move out of the creek 

 and into the lower reaches of its severed tributaries adjacent to a 

 drainage canal that received their diverted flow. 



INTRODUCTION 



Numerous sightings of alligators were made incidental to a five- 

 year study of Dutchman Creek estuary, a tidal creek and salt marsh 

 habitat located approximately 2 km west of Southport, Brunswick 

 County, North Carolina (Birkhead et al. 1977). Since the alligator is an 

 endangered species, and so little is known about the biology of northern 

 populations, we felt that these observations were of interest. The fact 

 that the habitat involved underwent a pronounced change after our 

 study began made the situation even more interesting. 



In its unaltered state, most of the freshwater flow into Dutchman 

 Creek came from its headwaters and from three principal tributaries to 

 the north and west. Tidal water flushed in and out twice a day by enter- 

 ing the creek from the Intracoastal Waterway, which bisected its lower 

 reaches. Thus, a typical estuarine condition was established, with a 

 salinity gradient ranging from an average of approximately 2 ppt in the 

 upper reaches to an average of 20 ppt near its mouth (Birkhead et al. 

 1977). Marshes adjacent to the lower reaches of the creek and tributar- 

 ies are flooded regularly with the tides. Spartina alterniflora is the dom- 



Brimleyana No. 6: 1 1 1-1 17. December 1981. Ill 



