One of those 'we are so lucky to be in such a beautiful city' type of days! http://t.co/pmkVhOHZ44
Killer whales, now more commonly known as orca from their latin name, Orcinus orca, are the most recognizable whale species with their striking black and white colours and impressively tall dorsal fins. Orca are the most widely dispersed mammal species aside from humans. They are highly intelligent, social and fascinating creatures who have adapted to many different habitats and food sources. In fact, every population of orca around the world is genetically distinct, having their own language, hunting strategies and food preferences. Due to these differing social behaviors, different populations will not interbreed with others.
Off the coastal waters of Washington, British Columbia and Alaska, there are 3 unique types of orca, the transients, residents and most recently discovered, the offshores. Killer whale research began here in the early 1970ʼs when the live capture industry was at its peak, removing whales from the wild to put into captivity. A scientist for the Department of Fisheries and Oceans named Michael Bigg, was the first to notice that there was more than one population of orca in the area, and that the different populations did not behave the same or interact with each other. He coined the terms residents and transients to describe the different types of orcas he encountered. The residents frequent coastal areas like the Straight of Juan de Fuca, Haro Straight and Puget Sound from spring until fall, while transients have a much larger home range, unpredictably visiting inland waters throughout the year.
There are two resident populations between Alaska and Washington, the Northern Residents who live around the northern half of Vancouver Island, and the Southern Residents who live around the southern half of Vancouver Island and northern Washington. Resident orca live in large family pods consisting of multiple related matrilines. The most distinguishing characteristic of residents is that they are strictly fish eaters. The two resident populations specialize on salmon, and when it comes to salmon they are picky, with over 70% of their diet consisting of the chinook species. Resident orcas tend to vocalize alot and use echolocation to find their food.
There are four transient populations that live between northern Alaska and Northern California. Transients live in smaller groups consisting of one matriline. Multiple matrilines may meet up for several hours or even days to cooperatively hunt, socialize and mate. Transients are mammal hunters, having a diet ranging from seals, sea lions, dolphins, porpoises and even other whale species. Transients tend to be very quiet, stalking their prey in silence, aiming for a surprise attack. In the North Pacific ocean, genetic analysis has revealed that these different populations of orca have not interbred for tens of thousands of years.
Offshore orca were first discovered in 1991, so little is known about them. As their name suggests, they spend most of their time far away from inland waters, making them very elusive and difficult to study. We have discovered that they travel in large groups, possibly up to a couple hundred, and are highly vocal. Recent research has made a big discovery about the offshores- they hunt sharks! The teeth of offshore orca are very worn down from the sandpaper-like skin of sharks that is covered in calcareous denticles, suggesting that sharks make up a large portion of their diet. Hopefully we will learn more about the habits of offshore killer whales in the future!
So all orca around the world belong to the same species much like humans, but they too have different races. In the biology field, these different races of orca are known as ecotypes. Unlike humans, the different killer whale ecotypes do not interbreed or even speak the same language. This segregation may eventually lead to naming each ecotype as a subspecies of orca. Interestingly, even though the different populations do not socialize or mate, they have also never shown aggressive behavior towards each other. Another interesting fact is that the different types of orca do not have any major different physical characteristics. They have the same average lengths and weights, and their teeth look the same as well.
Two subtle differences between transients and residents have to do with the shape of the dorsal fins and the saddle patches. Transient male orcas tend to have dorsal fins that come to a sharp point at the top, where resident males have a more rounded tip to their dorsal fin. Transient females have a sharply curved dorsal fin, with a pointy tip, whereas the resident females have a softer curving dorsal fin, with a rounded tip. The second difference has to do with the saddlepatch, which is the greyish-white mark behind the dorsal fin on every orcaʼs back. Transient orca have solid white or grey saddlepatches, which we call closed. Residents can have either a closed saddlepatch or an open saddlepatch, which is when there is a black shape running through the greyish-white area. This black area can look very different from whale to whale, and can even vary from the orcaʼs left side to their right.
Killer whales are very interesting marine mammals with sophisticated social structures and behaviors. We are forever learning more about these black and white top predators that live in all the worldʼs oceans. Who will be your favourite, the residents, transients or the offshores? Maybe all three!!