It’s our final week on Saturna Island for the summer. The resident orcas have been spending more and more time out in the open Pacific, and so we haven’t seen them for a week. It’s the longest we’ve gone without seeing them since we arrived! We have, however, seen Bigg’s orcas a few times, and we’ve heard them too! Which brings me to the subject matter of today’s post: What do I mean when I say Bigg’s, Transient or Resident orca? How are they different, and how can I tell them apart?
Let’s start with the very basic. Orcas are the largest species of dolphins, but scientists are not so sure anymore that they are, in fact, just one species. There are many different kinds of orcas, all of which have their own unique cultures, dialects, prey preferences, behaviours and looks. It’s thought that some of these may be different species altogether.
In British Columbia, we have 3 different kinds of orcas: residents, Bigg’s, and offshores. Offshores, like the name suggests, live away from the shore. They’re not seen very frequently, and little is known about them, so I won’t give them too much focus here. We see the residents and the Bigg’s orcas pretty frequently though.
My area of focus has been the resident orcas. British Columbia is home to two different populations of resident orcas – the Northern and Southern residents. Their geographic divide is, approximately, somewhere around Campbell River. They are fish specialists, eating a diet that is 97% salmon, and, more specifically, 78% Chinook salmon. They are extremely social, and the Southern Residents in particular can be quite boisterous. They are usually seen in large family groups, frequently vocalizing and performing all kinds of exciting surface behaviours.
On the other hand, the Bigg’s orcas, previously known as transients, eat marine mammals. Individual Bigg’s orcas may be marine mammal generalists, eating seals, sea lions, porpoises, and baleen whales, or they may specialize in particular types of marine mammals. Their group size typically ranges from 1 to 9 individuals, with about 4 or 5 being ideal. They need to keep their groups small and their behaviour stealthy, because the prey they hunt are smart, have good eyesight, and can hear the frequency range orcas vocalize in very well. They surface less frequently than residents, and change direction often. Sometimes, they even surface low to the water, in the troughs of waves, or at odd angles, presumably to disguise their towering dorsal fins from prey who may be watching for them above the surface. Bigg’s orcas rarely vocalize or engage in surface behaviours, except for during or after a hunt.
So behaviourally, these two groups of orcas are quite different. Their group sizes, movement patterns, and frequency of surface and vocal behaviour differ dramatically. But what about how they look?
Resident and Bigg’s orcas do look different, though perhaps not to the casual observer. Looking at orcas is much like looking at any animal species or breed for the first time – if you’ve only seen them a few times, they all look the same. But, if you do a little bit of practice, or spend a lot of time with them, you start to notice all of the subtle differences between them, and they begin to look very different. Here are the differences you should watch out for:
Bigg’s orcas are physically larger than resident orcas. Their dorsal fins and saddle patches, the characteristics used to identify individual orcas of all kinds, also differ from residents. The dorsal fins of resident orcas are often rounded at the top, and quite shapely. Many female residents have dorsal fins that tip backwards at the top, and most male residents have dorsal fins that appear fairly straight, or even swept forward. Bigg’s orcas typically have much more broad, triangular and pointed dorsal fins than resident orcas. The dorsal fins of some female Bigg’s look quite a lot like sharks.
Many resident orcas have what’s called an “open saddle”, which is to say, a grey saddle patch with a black finger or intrusion, while Bigg’s orcas only have solid grey, “closed”, saddle patches.
Lastly, Bigg’s orcas typically have more extensive scarring than residents, likely due to the hazards of hunting large marine mammals with sharp teeth. Here’s a couple photos of resident and Bigg’s orcas. See if you can spot the differences!
Now that you know how to tell the difference, you might be wondering, why would you need to? Well, for one thing, it makes it much easier to interpret the groupings of orcas that you see in the Salish Sea. Bigg’s orcas are very rarely seen in even remotely close proximity to the residents. They simply don’t interact with one another. So if you see a large group of resident orcas, followed shortly after by a smaller group of orcas, that smaller group is probably also resident orcas.
Another reason that it may be useful to know this is to know when you could and could not easily pursue legal (or other) action against boats that are misbehaving around the whales. In Canada, boats are supposed to stay 100m away from the orcas, and travel along beside orcas, rather than in front or behind. When it comes to the resident orcas, this is law, and is punishable with fines, and even loss of license to conduct whale watching tours. This is important for the resident orcas, because their population is very small. This population has numbered only about 80 orcas over the past few years, and are listed as endangered. While there are orcas all over the world, the number of orcas in each population is very important, because they don’t interbreed with other populations, and carry out their own unique cultures and roles in the ecology of their area. Our Southern Residents aren’t doing very well.
The Bigg’s orcas, however, are doing alright. They’re considered “threatened”, which, when listing species at risk, is the second least concerning listing. Ultimately, they could be doing better, but they seem to be doing alright, and their population is not in any immediate danger of extinction. Because they socialize only within their own community, have different culture and dietary preferences, and ultimately occupy a different ecological niche from that of the Southern Residents, the survival of the Bigg’s orcas is not tied to the survival of the Southern Residents, and so it makes sense from a government standpoint to legislate behaviour around the Southern Residents more strictly than behaviour around the Bigg’s orcas. This means that Bigg’s orcas do not, at this time, have any special laws applied to them, and boating around Bigg’s orcas is the same as boating around seals, sea lions, porpoises and humpback whales, legally speaking. It’s still recommended that you stay 100m away and flank the whales rather than chase them or cut them off, but it’s not a legal requirement. A case could be made against boats that are closer than this to a marine mammal under a Canadian law which states that it is illegal to disturb a marine mammal, but to win such a case you would need both proof that the boat was too close to the whales, as well as proof that the boat disturbed the whales. The law is a tricky business.
There is one final way to tell these two types of orcas apart, which I held out on telling you about until now. As a student of acoustics, I may be somewhat biased when I say that I think the coolest difference between these two groups is that they actually sound different, so much so that i don’t even need to have heard the calls they’re making before to know which group I’m listening to. I do find it helpful to make associations with more familiar sounds when I listen – I listen for high pitched squeaks, squeals and honks when hearing residents, and sad or whining cats when I hear Bigg’s. I’ve included an example of each below from recordings from the SIMRES hydrophone array – have a listen and decide for yourselves what you think they sound like!
A short selection from J and K pods passing through Boundary Pass in the night.
Bigg’s orcas celebrating a successful hunt in Boundary Pass.
Photos by Kristen Kanes