IRVINE ET AL ; MOVEMENTS AND ACTIVITIES OF ATLANTIC BOTTLENOSE DOLPHIN 



a 

 o 



o 



Q 



7 - 

 6 - 

 5 

 4 



3 

 2 



1 - 



Number 

 of Groups 



10 



A) 



19 



22 



38 



90 



57 



33 



20 



48 



52 



Figure 3. — Compilation of bottlenose 

 dolphin sighting data by month, from 

 boat surveys: A) Average number 

 of dolphins sighted per group with 

 standard error ivertical lines) and 

 numbers of groups sighted mumeralsi 

 for each month. B) Number of field 

 hours and boat survey davs (numerals). 



2 



0) 



125- 

 100- 

 75 - 

 50 - 



25-1 



Survey 

 Days 



Bl 



M 



17 



20 



J A 

 1975 



12 



O N D 

 MONTH 



20 



19 



M 



A M 

 1976 



Home Range 



Resightings of tagged bottlenose dolphins sug- 

 gest that at least some were year-round residents 

 of the study area (Figure 4). We recaptured 11 of 

 the 12 animals tagged in 1970-71 by Irvine and 

 Wells (1972) and identified them by freezebrands, 

 tag scars, or dorsal fin shape — strongly implying 

 that some bottlenose dolphins may remain in the 

 area for several years. The existence of resident 

 bottlenose dolphins has previously been widely 

 proposed (Caldwell 1955; Caldwell and Golley 

 1965; Norris and Pryor 1970; Saayman et al. 1972; 

 Saayman et al. 1973; Wursig and Wiirsig 1977, 

 1979; Wursig 1978; Saayman and Tayler 1979; 



Norris and Dohl 1980b; Shane and Schmidly 

 footnote 5). 



The home range of the bottlenose dolphins in 

 the study area appeared to extend south from the 

 southern edge of Tampa Bay to Big Pass ( Figure 5; 

 see also Wells et al. 1980), and to include inshore 

 areas and waters up to 1 km into the Gulf 

 of Mexico. No tagged bottlenose dolphins were 

 observed more than 1 km offshore; however, 

 survey trips rarely extended farther than 3 km 

 offshore. At their apparent northern boundary, 

 tagged animals terminated northerly movements 

 at the edge of Tampa Bay by turning either east or 

 west (Figure 2). Groups containing identifiable 

 naturally marked bottlenose dolphins, apparently 



FIGURE 4.— Total biweekly sightings of 

 selected tagged bottlenose dolphins; 

 one sighting per day included. Twenty- 

 three of these sightings were reported 

 by other observers. Arrows indicate 

 capture dates. Sighting locations of 

 dolphins marked with an asterisk are 

 shown in Figure 5. 



Dolphin 

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Jan ' Feb ' Mar ' Apr ' Moy 'June' July ' Aug Sept' Oct ' Nov ' Dec | Jon ' Feb ' Mor ' Apr ' Moy June July 



1975 976 



675 



