Vocal repertoire and acoustic behavior of the isolated AT1 killer whale subpopulation in southern Alaska

• Published in: Canadian Journal of Zoology
• Main Authors: Saulitis, Eva L, Matkin, Craig O, Fay, Francis H
• Format: Article in Journal/Newspaper
• Language: English
• Published: Canadian Science Publishing 2005
• Subjects: Killer Whale; Orca; Orcinus orca; Alaska; Killer whale
• Online Access: http://dx.doi.org/10.1139/z05-089; http://www.nrcresearchpress.com/doi/pdf/10.1139/z05-089

Killer whales, Orcinus orca (L., 1758), in the North Pacific are classified as three genetically distinct ecotypes: residents (fish-eaters), transients (mammal-eaters), and offshores (probable fish-eaters). Within the transient ecotype, three putative subpopulations have been identified by genetic analysis: West Coast transients, Gulf of Alaska transients, and AT1 transients. Here, we examine the behavior and vocalizations of the AT1 transients, which are found only in the Prince William Sound/Kenai Fjords region, to determine if their acoustic behavior distinguishes them from other genetically distinct transient subpopulations. We identified 14 discrete, pulsed calls in the vocal repertoire of the AT1 transients. These calls were entirely different than those of West Coast and sympatric Gulf of Alaska transients. Despite their large call repertoire, AT1 transients were silent most of the time, utilizing a foraging strategy of stealth, acoustic crypsis, and passive listening for locating marine-mammal prey. Unlike resident killer whales, AT1 transient vocalization types were context specific. For example, lone AT1 transients produced long-distance, high-amplitude pulsed calls in stereotyped sequences to locate other AT1 whales. In contrast, hunting individuals emitted low-amplitude pulsed calls to maintain contact with group members. The repertoire and call-usage patterns of the AT1 transients are consistent with genetic evidence that they are a unique, reproductively and socially isolated subpopulation in danger of extinction.