Miller and Baltz: Seasonal trends and foraging habitat of Tursiops truncatus 
83 
5 10 15 20 25 30 
Temperature (°C) 
0.6 
r 1.2 
cn 
c 
CD 
cr 
<D 
> 
ro 
CD 
cr 
■< 
Turbidity (NTU) 
Figure 1 
Foraging suitability curves for bottlenose dolphins 
( Tursiops truncatus) observed in northern Gulf of 
Mexico bays from June 1999 to May 2002 for tem- 
perature, dissolved oxygen, and turbidity (in nephelo- 
metric turbidity units [NTU]). Vertical bars indicate 
frequency of overall observations (black) and foraging 
activity (white) for each given interval. Black lines 
indicate the relative suitability of variable values 
for foraging activity. 
50 100 200 400 
Distance from shore (m) 
400 + 
4 6 
Depth (m) 
0-4 5-9 10-14 15-19 20-24 25 + 
Minimum group size 
Figure 2 
Foraging suitability curves for bottlenose dolphins 
( Tursiops truncatus) observed in northern Gulf of 
Mexico bays from June 1999 to May 2002 for distance 
to shore, depth, and minimum group size. Verti- 
cal bars indicate frequency of overall observations 
(black) and foraging activity (white) for each given 
interval. Black lines indicate the relative suitability 
of variable values for foraging activity. 
detection of predators. However, it should be noted that 
on an overall basis most of the foraging occurred in less 
turbid waters. 
It is logical that the movement and distribution of 
prey are important features for characterizing dolphin 
foraging habitat. Larger group sizes were identified as 
an important factor in differentiating sightings based 
on foraging activity (Table 4, Fig. 2). Nevertheless, 
it is difficult to know whether increased group sizes 
are formed in response to favorable environmental 
conditions for prey congregation or whether individu- 
als gather together as part of a strategy to increase 
