While reports of residency are ubiquitous in the literature, measurements 

 of geographic area commonly used by individuals are rarer. Researchers at 

 two study sites have provided precise estimates of dolphin ranges. On the 

 California coast, individual dolphins commonly range over > 50-483 km of 

 coastline (Defran et al. in press) in a 0.5-km-v^ide strip (Hansen and Defran 

 1989). Following a 1982 El Nifto-related range extension, some individuals 

 have been seen to make a 1,340 km round- trip from Sam Diego to Monterey 

 over about 70 days (Wells et al. 1990). Hansen (1983) considered some 

 dolphins to be resident to the 155-km strip around his La JoUa study site 

 during his 17 month study. Nine individuals have been consistently 

 resighted in Monterey through 1993 "suggesting a degree of site fidelity not 

 previously documented for Pacific coast bottlenose dolphins" (Scott et al. 

 1993). Range boundaries may be delineated by depth or distance from shore 

 (offshore boundary, Weller 1991), temperature (northern boundary. Wells et 

 al. 1990), and physical or hydrographic features (southern boundary, Caldwell 

 et al. 1991). No seasonal movement patten\s have been found (Hansen 1990). 

 Hansen (1990) notes that range boundaries delineated by topographic featvu-es 

 "are not inviolate and may in fact just correlate with preferred areas". 



On the Florida gulf coast, the population is hypothesized to be structiired 

 into geographically adjacent "communities" with some social mixing and 

 geographic overlap (see summaries in Scott et al. 1990a, Wells 1991). The 

 Sarasota Bay area community consists of approximately 100 individuals, 

 ranging over 100 km^ to about 1 km offshore (Wells 1991). Range boundaries 

 seem to be delineated by water depth (Wells et al. 1987). Individuals in 

 different age and sex classes have different sized "core use areas" which seem 

 to be on the order of 50-100 km^ (Wells 1991). Within the community home 

 range, individuals show tendencies for seasonal habitat use patterns probably 

 related to prey and predator movements (Irvine et al. 1981). 



In the present study, radio-tagged dolphins had two distinct range areas 

 (Fig. 6). This is consistent with Gruber's (1981) hypothesized "extended herd 

 home ranges" with shared borders in the Port O'Cormor area. For example, 

 FB515 stayed mainly in the NE section of Espiritu Santo Bay and FB514 in an 

 adjoining area in SW Matagorda Bay (Fig. 6c). Both were originally captured 

 together in the small overlapping area. Ranges for FB518, FB521, FB511, and 

 FB522 all overlap strongly. These dolphins were caught together (FB518, 

 FB521) or in areas only 4 km apart (FB511, FB522). A third "extended herd 

 home range" to the northwest along Matagorda Peninsula is suggested by the 

 lack of resigh tings of 10 of the 11 individuals captxired there (Appendix 3f). 

 These 10 were not seen in the following year, perhaps due to lade of effort 

 northwest of our primary study area; data from later surveys indicate that 

 some of them may have been present, as discussed below. The 11th dolphin, 

 FB522 (radio-tag #10), seldom frequented that area in the remainder of his 



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