Estuarine-Inhabiting Alligators 113 



RESULTS AND DISCUSSION 



Although alligators were observed during every month of the year, 

 the majority of sightings (76%) occurred between April and July (Table 

 1). The few fall and winter sightings were probably of a single alligator 

 that inhabited the upper reaches of Dutchman Creek below the canal 

 rights-of-way in the vicinity of station 2. 



Prior to the diversion of the headwaters and principal tributaries of 

 Dutchman Creek (sampling year 1971-72), all alligators sighted were 

 downstream from what were then the proposed canal rights-of-way 

 (Table 2). After the freshwater input was diverted (sampling years 1972- 

 76), alligators virtually disappeared from the lower reaches of Dutch- 

 man Creek itself, and the majority of sightings were made in or along 

 the northwestern and western side of the freshwater drainage canal, par- 

 ticularly in the vicinity of the severed headwaters and tributaries. De- 

 spite these spatial shifts, alligators appeared to be randomly distributed 

 within the salinity regimes that were present in the estuary before and 

 after alterations were made (Table 3). 



Alligator sightings were bimodal with respect to water temperature 

 (Table 3). Although most alligators (67%) were sighted when water 

 temperatures were between 22°C and 30°C, several (26%) were seen 

 when water temperatures were in the teens. The latter observations fre- 

 quently involved animals that were basking during the spring, a season 

 when air temperatures were undoubtedly higher than water temperatures. 



Most of the alligators whose size could be estimated (Table 4) 

 appeared to be between 1 and 2 m total length. The smallest individual 

 seen was about 0.6 m long, while the largest appeared to be in excess of 

 2.4 m. 



Since alligators observed during the course of this study were not 

 marked, long term movements of individual animals could not be ascer- 

 tained. Nevertheless, our sightings provide evidence for spatial shifts in 

 the population inhabiting the Dutchman Creek estuary following block- 

 age and diversion of its headwaters and principal tributaries. We suggest 

 these reptiles may have moved because they required access to fresh 

 water. 



It is well known that tidal creeks and their associated salt marshes 

 are highly productive habitats that serve as nursery areas for large 

 numbers of fishes and shellfishes (Weinstein 1979). However, Chabreck 

 (1971) and Joanen et al. (1971) noted that immature and hatchling alli- 

 gators that remained under saline conditions for extended periods of 

 time experienced significant weight losses despite the fact that food was, 

 or appeared to be, readily available. Both authors attributed weight loss 

 to reduced food intake. It is entirely possible that estuarine-inhabiting 

 alligators can only make use of this productivity by either allocating 

 their feeding activities to periods of low tide or by hunting in the brack- 

 ish parts of the estuary where salinities are low and concentrations of 



