category but spent 28% of his time at the surface. A juvenile male, which did not move a 

 long distance had 45% of its discrete dives as ZDDs but spent only 19% of its time at the 

 surface. These contrasts show that long-range movements and speed do not by themselves 

 dictate surface resting patterns and that percentage ZDD is an important but not exclusive 

 indicator of total time spent at the surface. Also, the frequency of surface resting during 

 Periods 2 and 3 probably contributed to the high number of messages received during those 

 periods. 



Often zero duration dive (ZDD) messages occurred one after another, confirming 

 long periods of surface resting. The longest series of zero duration dive messages accounted 

 for a total of 11 min. spent continuously at the surface by PTT #833. With just a few dives 

 of less than 20 s, prolonged surface resting was apparent for up to 12 min. for PTT #823, 

 10 min. for PTT #839 and 7 min. for PTT #840. Often consecutive monitored passes up 

 to six hours apart showed long periods of surface resting. Figure 78 demonstrates the 

 relationship between the percentage of time spent submerged and the number of zero 

 duration dives. As suspected, large numbers of zero duration dives were recorded most 

 frequently during summary periods which reported a higher percentage of surface time (low 

 percent of time spent submerged). The strong similarity in the equations fitted to data for 

 PTT #823 and PTT #839 suggest that this relationship is reasonably stereotyped, especially 

 considering the differences in the number of dives and average dive durations for these two 

 animals. 



The Relationship of Speed and Respiration Patterns 



Figures 79 - 82 show the chronological relationship of average dive duration, speed 

 and the number of dives in a 6-hour summary period for the four whales with the largest 

 sample sizes. It is important to re-emphasize that speeds used here are minimum estimates 

 based on calculated distances between Argos acquired locations. Thus, our calculated high 

 speeds may be the real result of extremely directed (linear) swimming activity or errors in 

 Argos locations. 



Figure 83 shows the relationship between average dive duration, number of dives and 

 speed for all 6-hour summary periods and for all whales. An upper limit to this curve is 

 described by the function: 



1990 average duration of dive =# seconds in period/# dives 

 AVG DUR = (21,600)/(#DIVES) 



118 



