GLOSSARY A B C D E F G H I J K L M N O P Q R S T U V W X Y Z breach occurs when a whale leaps out of the water, exposing two-thirds or more of its body. bull a sexually mature male; can be identified by its large size and tall dorsal fin, which is at least 1.4 times taller than its width at the base; bulls reach physical maturity at about 20 years of age. blowhole nostril located on the top of the head. During dives the blowhole is sealed by a nasal plug which is retracted by fast-acting muscles upon surfacing for breathing. calf a young-of-the-year, typically born in fall or winter. clan one or more pods that share a related dialect; pods within a clan have probably descended from a common ancestral group and therefore are probably more closely related to each other than to pods from other clans. clicking a series of close-spaced, broad spectrum sounds, mainly at very high frequencies, made when echolocating. Each species has distinct frequencies and patterns of clicks. community comprises all pods that travel together; pods from different communities have never been seen together. countershading protective coloring in which the dorsal (upper) surface is darker than the ventral (lower) surface so that whether viewed from above or below, the whale appears evenly coloured and inconspicuous. cow a sexually mature female, usually with at least one offspring; often seen with juveniles following; can be confused with large juvenile males. dialect a unique set of discrete calls made by an individual whale and fellow pod members; dialects of most resident pods can be distinguished either by ear or with a sound analyzer. discrete call a type of communication vocalization that sounds the same each time it is produced; on average, resident pods produce about twelve different types of discrete calls. dorsal fin the fin along the midline of the back of most whales and dolphins. echolocation the process by which killer whales and other toothed cetaceans use vocalizations to obtain information about their surroundings; similar to SONAR, echolation involves the production of rapid, high-frequency clicks that echo off objects in the whale's path. eye patch the elliptically-shaped white patch located above and behind a whale's eye. flukes the horizontal projections forming the tail of the whale. fluking act of raising the body on stones in shallow water near the shore. haul-out a rocky reef or beach where seals or sea lions climb out of the water to rest. hydrophone an underwater microphone used to listen to and record whale vocalizations. juvenile an immature whale of either sex. keel distinctive bulge on tail stock near flukes, can be on upper side, underside or both. leapfrogging a whale-watching practice involving the repeated placement of a boat directly in the whale's path; may contribute to more underwater noise and disturbance than other whale-watching techniques. lobtailing making a loud splash by forcefully slapping the flukes against the surface of the water. maternal genealogy a family tree showing the ancestry of an individual through its mothers relatives; also known as a matriline. matriarch the eldest female in a matrilineal group, pod, or subpod. matrilineal group the basic social unit of resident killer whales, composed of a mature female and her immediate descendents; descendents may include mature males and mature daughters and their offspring. migration regular journeys of animals between one region and another, usually associated with seasonal climatic changes or breeding and feeding cycles. offshore killer whales a little-known population of killer whales, found mostly in offshore waters off British Columbia but also identified in California, Washington, and southeastern Alaska; more closely related genetically to residents than to transients; appear to travel in generally larger groups than residents or transients. pec-slapping raising a pectoral fin out of the water and slapping it noisily against the water's surface. pectoral fins paired, paddle-shaped forelimbs used for stability and steering, also called flippers. penduncle-slapping also known as tail-breaching, throwing the rear portion of the body out of the water and slapping it sideways onto the surface, or on top of another whale. pod in resident killer whales, a group of maternally related individuals that tend to travel together; in transient killer whales, the term "group" is used in preference to "pod" because groups are not necessarily made up of related animals. resident killer whales a form of killer whales that feeds preferentially on fish, especially salmon, and has a very stable social structure. saddle the grey pigmented area at the posterior base of the dorsal fin. spout or blow, a cloud or column of moist air forcefully expelled through the blowhole when the whale surfaces to breath. sprouter an adolescent male whose fin is undergoing a rapid spurt of growth, this usually takes place around 15 years of age. spyhop a behaviour where a whale raises its head vertically above the water, then slips back below the surface; a spyhop seems to be a means of obtaining a view above the surface. stranding the coming to land, either dead or alive of a cetacean. subpod one or more matrilineal groups that temporarily separate as a unit from a pod; members apparently always travel together; term relevant mainly to resident whales. tailstock also called caudal peduncle, the tapered rear part of the body, from just behind the dorsal fin to just in front of the flukes. transient killer whales a form of killer whales that feeds preferentially on marine mammals and has a looser social structure than that of residents; transients also differ from residents in dorsal fin shape, group size, behaviour, vocalizations and genetics. whale encounter an occasion when one or more identifiable individuals have been located. All pictures and audio © Vancouver Aquarium Marine Science Centre 1999