Description 
The main identifying characteristics of Killer Whales are the distinctive black and white pattern, blunt head, and tall dorsal fin in the middle of the back. Adult males are larger than females - the maximum recorded length for a male is 9.0 m, compared with 7.7 m for a female. However, the average length of adult individuals in British Columbia waters is much smaller than these maximum lengths. The tall dorsal fin of adult males is triangular in shape and may reach up to 1.8 m in height, while in juveniles and adult females it reaches 0.9 m or less and is generally more falcate (hooked like a sickle). Furthermore, the pectoral fins and tail flukes are larger in adult males, and the tail fluke bends downwards.

Canadian Distribution of the Killer Whale (shown in red) 1,2 Distribution is approximate and not intended for legal use. 1Author: Canadian Wildlife Service, 2004 2Data Sources: The main source of information and data is the COSEWIC Status Report. In many cases additional data sources were used; a complete list will be available in the future.

Killer Whales are cosmopolitan, having been observed in all oceans of the world, but they generally concentrate in colder regions and in areas of high productivity. They are found in all three of Canada's oceans, as well as occasionally in Hudson Bay and in the Gulf of St. Lawrence, but they appear to be uncommon in the Atlantic and Arctic. In British Columbia, they have been recorded throughout almost all salt water (and some fresh water) areas, including many long inlets, narrow channels and deep enbayments. Both resident and transient Killer Whales have been recorded year-round off the Pacific coast. The two types differ in morphology, genetics, behaviour, and diet. Residents feed on fish, and their distribution is closely tied with peak abundance of various species of salmon prey. Transients feed on marine mammals. There are two populations of resident Killer Whales: northern residents, and southern residents. Both populations are small, and have low potential rates of increase.

The northern resident population has been growing steadily in size since the 1970s (when live-capture fisheries stopped and shooting declined). It increased over 20 years to 216 individuals in 1997, but recent data suggest that the population since declined by approximately 7% over the past 4 years.

Habitat 
Killer Whales do not appear to be limited by such habitat considerations as depth, water temperature, or salinity. They are found in all oceans, in water temperatures ranging from below 0°C to warm tropical waters. They have been recorded in water ranging from shallow (several metres) to open ocean depths. They will occasionally spend considerable time in brackish water and will even enter rivers.

Biology 
The following description of the biology of the Killer Whale is based on data from both the northern and southern "resident" populations, since these are the most studied. Life history characteristics, such as gestation period, may vary between populations. Both males and females reach sexual maturity at 15 years of age on average. Reported gestation periods, often established with captive animals, have ranged from 12 to 17 months. The interval between calving is usually about 5 years (ranging from 2 to 12 years). Length of calves at birth ranges from 218 to 257 cm. Calving occurs year round, but appears to peak between fall and spring. Mortality rates vary with age. Neonate mortality (from birth to six months of age) is high - was even as high as 50% in one study. From birth, the average life expectancy is about 29 years for females and 17 years for males. I n general, Killer Whales feed on a wide range of prey, including squid, octopus, bony and cartilaginous fish, sea turtles, sea birds, sea and river otters, dugongs, pinnipeds, other cetaceans, and occasionally terrestrial mammals such as deer, moose and pigs. However, individual populations appear to specialize on particular types of prey.

Threats 
Given their low population sizes and low potential rates of growth, Killer Whales are potentially at risk from anthropogenic (human-related) influences including immunotoxic affects of persistent toxic chemicals, and reduction in availability of prey concomitantly caught by sport and commercial fisheries. Significant organochlorine levels have been measured in their blubber, but concentrations are lower than those reported for the transient and southern resident populations. It is also possible that the large and growing commercial and recreational whale watching industry on the west coast may be having an impact, though such impacts are as yet unclear. Northern residents are subject to high levels of human interaction (boat traffic) that may have negative consequences on the population. Fishing boat/human interactions include direct takes (whaling, culling), live-capture fisheries, entanglement in fishing gear, collisions with vessels, and exposure to oil spills. Although the largest fisheries of whales were discontinued in the early 1980s and 1990s, small numbers are probably still taken. Among the natural factors that may be limiting the whale's populations are periodic events such as mass strandings or entrapments in narrow inlets or ice, which have the potential to drastically reduce numbers locally.

Protection 
The Killer Whale, Northern Resident Population, is protected under the federal Species at Risk Act (SARA). More information about SARA, including how it protects individual species, is available in the Species at Risk Act: A Guide.

The Killer Whale Northeast Pacific northern resident population is protected by the Marine Mammal Regulations under the federal Fisheries Act. These regulations make it an offence to kill, harm, or harass marine mammals. Whale-watching guidelines have been developed by Fisheries and Oceans Canada in collaboration with several other organizations. Additional public outreach measures are also being taken to minimize negative interactions between boats and whales.

Other Protection or Status 
The Killer Whale is listed on Appendix II of the Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES), which sets controls on the international trade and movement of species that have been, or may be, threatened due to commercial exploitation. International trade of Killer Whales, or parts thereof, by any countries which are parties to CITES requires export permits from the country of origin.