Matkin et al,: Ecotypic variation and predatory behavior among Orcinus orca off the eastern Aleutian Islands 



79 



on morphology and behavior and determined from field 

 observations and photographs were consistent with the 

 genetic analysis. For the 26 encounters that yielded both 

 genetic and acoustic data, the two kinds of data provided 

 identical classifications of lineage. 



All 35 killer whales sampled in the False Pass- 

 Unimak Island region had transient haplotypes. Eight of 

 the nine samples collected in the area in 2003 had the 

 GATl haplotype, which was first identified in transient 

 killer whales from the northern Gulf of Alaska area in 

 or near Kenai Fjords and Prince William Sound. The re- 

 maining sample contained the ATI haplotype, formerly 

 sequenced only in members of the ATI transient popula- 

 tion of the Prince William Sound area. In 2004, 14 of 26 

 killer whales sampled in the False Pass-Unimak Island 

 area had the GATl haplotype, and the remainder had a 

 GAT2 haplotype, a similar but not identical haplotype 

 known to exist at a low frequency in the Gulf of Alaska 

 transient killer whale population (Barrett-Lennard, 

 2000). Eleven of the 12 transient whales sampled in 

 the summer months during 2001-2004 in the eastern 

 Aleutians had the GATl haplotype, and the remaining 

 one had the GAT2 haplotype. 



Ecotypic parameters 



Resident killer whales During a majority of our encoun- 

 ters, resident killer whales tended to be found and to 

 travel along or near the 200-meter depth contour (Fig. 

 2A). This contour corresponds to a steep drop-off from 

 the coastal shelf. 



Approximately 929c of the encounters with killer 

 whales during our summer surveys from Unimak Pass 

 to Umnak Island were with whales determined by ge- 

 netics, acoustics, or group association to be of the resi- 

 dent ecotype; however, this ecotype was not encountered 

 in the spring surveys east of Unimak Pass (Table 1). 

 A minimum of 901 resident whales used the Eastern 

 Aleutians during the study; this count was based on 

 individuals identified from photographs taken from 

 2001 through 2004. Of these individuals, 143 were seen 

 only once during the study, and the remainder were 

 repeatedly identified. The number of new, previously 

 un-photographed whales observed each year declined 

 from 534 whales in 2002 to 211 whales in 2003, to 156 

 whales in 2004 (Table 3). The decline in new whale 

 sightings each year may indicate that we have identi- 

 fied the majority of whales that use this area during 

 the summer months; however, there may be hundreds of 

 whales that occasionally use the area but have not been 

 encountered. The study area is likely only a portion 

 of the range of the identified resident whales; several 

 whales were matched with individuals seen in photo- 

 graphs taken in the Pribilof Islands over 200 miles to 

 the west. 



The numbers of individuals that could be positively 

 identified in each resident ecotype encounter ranged 

 from 4 to 109. A total of 347 whales were placed in 82 

 tentative matrilines which consisted of a reproductive 

 female and her offspring of both sexes. These matrilines 



were determined from repeated association of individu- 

 als in both photographs and field observations. This 

 method of determining matrilines was demonstrated 

 effective in other population studies of resident killer 

 whales (Bigg et al., 1990; Matkin et al., 1999b). Most of 

 the matrilines comprised two generations (mother and 

 offspring), although some included a probable grand- 

 mother. All matrilines were of consistent composition 

 and maintained their structure over the course of the 

 study, which has been the case in all other resident 

 populations studied to date (Matkin et al., 1999a; Ford 

 et al., 2000). The structure of the population was in- 

 ferred from 41 groups of one or more matrilines that 

 appeared to be longer-term associations. These groups 

 could be considered as tentative pods (as defined by 

 Bigg et al., 1990). Twenty-one of these groups, contain- 

 ing 266 whales, were sighted frequently enough that 

 basic age and sex classes could be determined. These 

 groups contained 65 adult males (2A A^c), 105 females 

 or immature males (39.5%), and 96 juveniles and calves 

 (36.1%). These proportions of males, females and imma- 

 ture males, and juveniles and calves are comparable to 

 those observed in other resident populations in Alaska 

 and British Columbia (Leatherwood et al., 1990). 



There was no evidence that resident killer whales 

 consumed marine mammals. Whales belonging to the 

 resident ecotype were observed consuming fish only 

 during infrequent observations of predation (halibut 

 were identified from samples, and salmon were probable 

 from visual observations only). Much of the predation 

 by resident killer whales was not visible at the sur- 

 face and therefore prey samples could not be obtained. 

 Resident whales were the only killer whales observed 

 removing fish from the lines of commercial fishermen 

 and observed following and feeding on fish discards 

 from trawlers. 



Transient killer whales A total of 165 individual killer 

 whales were determined to be transients from encoun- 

 ters during 2001-2004 (Table 4). A majority of these 

 whales (114) were photographed during the May-June 

 field work in the False Pass-Unimak Island region in 



