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Tales from the tide pool
British Columbia has many iconic species, but one of the best known lives just off the coast – the Orca whale.
Orca whales are also referred to as Killer whales and Blackfish. Historically, Orcas were very misunderstood and thought to be terribly dangerous; however research on these exquisite mammals began to show just how remarkable and complex they really are.
These black and white beauties are found around the world, but there are three different ecotypes that exist off the coast of British Columbia – the Residents, Bigg’s and Offshores.
One of the best ways to separate Offshores, Bigg’s and Residents, apart from a few physical differences, is by the food they prefer. Not much is really known about the Offshores as they spend so much time far off the coast. However, it was recently confirmed that they can and do eat sharks, particularly sleeper sharks.
Bigg’s (formally known as Transients), named after Canadian scientist Dr. Michael Bigg, eat other marine mammals. These mammals include everything from dolphins to seals to even other whales. Bigg’s also enjoy playing with their food and can be seen putting on extravagant shows by throwing their dinner high into the air – a rather morbid, but oddly fascinating thing to watch.
Finally, the Residents, which can be seen throughout the gulf Islands and off Oak Bay (mostly in late spring and summer) love fish. Residents eat many kilograms (some 225 kilograms a day) of salmon, their favourite being Chinook.
Residents find salmon through echolocation, a process similar to that used by bats, where they send out a “ping” and wait for a return signal off a fish.
Echolocation is a very important tool for Orcas along with the other ways that they use and produce sound. While there is much to discuss – like the Orca’s social structure, intelligence or behaviours – I will focus on one amazing aspect of this creature, how they “view” their world – through sound.
Humans are extremely visual beings and tend to use our sense of sight above our other senses to explore our world. Orca whales, on the other hand, rely on sound, especially to communicate with family and for finding prey. Orca whales make several different sounds including clicks, whistles and calls; the tone, frequency and pitch of these sounds can tell scientists which ecotype (and often pod) of whale is vocalizing.
Different groups of Orcas can sound very different to a trained ear. For example, the Southern Residents are split up into pods J, K and L. Each of these pods can speak to each other, but have a unique dialect. An analogy would be like a Brit, an Aussie and a Canadian all speaking to each other – they all speak English, all understand each other, but there are some words or phrases that the other groups may not fully comprehend. Although Residents and Bigg’s are often inhabiting the same area, they don’t speak to each other at all, not even realizing they are similar species.
The vocalizations of an Orca are beautiful, almost haunting. In some portions of their calls you can hear their emotions and almost sense how they feel. Vocalizations of marine mammals are captured by underwater microphones, called hydrophones that passively listen to the world around them. Depending on the frequency of the hydrophone, it can pick up an Orca from several kilometres away. Hydrophones are used not only because they are passive instruments, but also because Orcas only spend about five per cent of their time at the surface, thus visual surveys and photo identification can be difficult.
Since humans are such visual creatures, hydrophone data can also be displayed as a spectrogram, which allows scientists to see the frequency of the sound as a graph. Certain types of vocalizations have certain frequency outputs, so trained scientists can look through spectrograms and identify interesting sections to listen to.
Hydrophones also pick up human-induced noise, such as shipping and sonar. More research is underway to better understand the effect of anthropogenic noise on marine mammals, specifically those that vocalize and use echolocation, like Orcas.
To hear the vocalization of Orcas and other whales log onto oceannetworks.ca and explore Ocean Networks Canada’s audio gallery (in the “Sights and Sounds” page) – be prepared to be amazed.
To learn more about whales and to report if you see one, visit the BC Cetaceans Sightings Network, run through the Vancouver Aquarium at vanaqua.org.
Combining her passions for education and the marine ecosystem Natasha Ewing inspires K-12 teachers and students to incorporate hands-on experiential ocean science into the classroom for Ocean Networks Canada.