Goebel et al.: Diving patterns and foraging locations of female Callorhmus ursinus 



175 



to depths greater than 75 m and then once near the 

 shelf break, she began diving to shallow depths. 



Female mass and depth of dive 



Seven of the nine females were weighed at instrument 

 deployment, and eight were weighed when the instru- 

 ment was recovered (Table 2). All females weighed 

 twice showed a mass gain (range 0.3-4.1 kg). Time at 

 sea ranged from 91 to 295 hours. Length of time at 

 sea was not correlated with diving patterns or mass 

 of the female (r 2 0.0). No correlation was found be- 

 tween mass of individuals and their diving patterns 

 (r 2 0.0). 



The mean maximum depth of dive for each deep diver 

 was greater than 75 m whether considering day dives 

 or night dives (Table 3). The mean maximum depth of 

 dive for the shallow-diving females was less than 75 m 

 (Table 3). When considering only night dives, shallow- 

 diving females showed mean maximum depths of less 

 than 50 m. 



Two of the deep divers (195 and 651) showed no dif- 

 ference in depth of dives between day and night. The 

 other seven females showed a significant difference in 

 depth of dives between day and night. Six females 

 dived deeper during the day than at night. The seventh 

 (566) had significantly deeper dives at night than dur- 

 ing the day (Table 3). 



Time from shore to 



the first dive bout and return 



The time between departure from shore and the first 

 dive bout was highly variable, as was the time between 

 the last dive bout and the return to shore (Table 2). 

 These times ranged from about 3 to 34 hours. Mean 

 time to first dive bout was 15.06 hours (SD 10.26) and 

 the mean time from last dive bout to shore was 13.94 

 hours (SD 5.88). There was no significant difference 

 between the time to first dive bout and the time from 

 the last dive bout (Mann-Whitney P = 0.86). 



There were no differences in either the time to the 

 first dive bout or the time from the last dive bout when 

 comparing shallow divers with deep divers. The mean 

 time to the first dive bout was 12.30 hours (SD 8.74) 

 for shallow divers and 18.51 hours (SD 12.26) for deep 

 divers (Mann- Whitney P = 0.46). The mean time from 

 the last dive bout to shore for shallow divers was 11.92 

 hours (SD 6.29) and for deep divers was 16.46 hours 

 (SD 4.93; Mann-Whitney P = 0.54). 



Foraging patterns 



Deep divers showed a much lower percentage of dives 

 at night than the shallow divers (Table 4). Females 566 

 and 695 made less than 50% of their dives at night. 

 In general, shallow divers made greater than 70% of 

 their dives at night (females 214 and 713 >90%) and 

 deep divers less than 70%. 



