Monday, February 22, 2016

Ghost Face Killer (Whales)

December's post got the Depth and Taxa crew thinking. We talk an awful lot about fish and invertebrates on this blog. Of our 32 posts only three directly refer to marine mammals. While it's great that we're bringing the less publicly well-loved species into the spotlight; it's sad because the ocean's mammals are astonishing. Whales, dolphins, porpoises, seals, sea lions, walruses, and sirens (the manatee kind, not the Odyssean) all exhibit remarkable adaptations for a class of animals that arguably don't belong underwater. So in the interest of fairness and the spirit of deeper understanding, let's talk about the biggest, the baddest, the black and white-enest of the dolphins; Orcinus orca, the Killer Whale.

They're like the pandas of the sea! If pandas ate exclusively flesh...
and hunted in groups... and had complex social structures... 
They're like the wolves of the sea!
Courtesy: Matthew Allen via Flickr

Okay so the first thing you might be wondering is how we can call them killer whales if they're dolphins? Well the word "whale" is deceptively complicated. See, back when the common conscious was still in its "everything that swims is a fish phase" a whale was just anything really large that you saw or caught in the ocean. More recently whale has mostly been used to mean any large species of cetacean (pronounced: set-ay-shun). If you've ever called something a whale, porpoise, or dolphin; it's a cetacean. Dolphins are a specific family within the cetaceans, so orcas are both whales and dolphins. 

Just like humans, orcas can be found all over the globe; from the tropics to the poles. They live in groups comprised of their relatives and close associates, just like us. They're the apex predator in their environment, just like us... They live 50-60 years but can get over 100... Hm these similarities are starting to get a bit strange.

Okay, this is officially weird now. 
Courtsey: Douglas Muth via Flickr
The truth of the matter is, humans and orcas are both extremely successful because of our large, wrinkly brains and penchant for caring about others of our own species. In humans the prime example of this one-two punch of emotional intellectualism is just how much listening to "Hello"  makes us want Adele to find happiness <sniffles>. In orcas it's their ability to form what are called ecotypes.

There are at least ten orca ecotypes between the northern and southern hemisphere, and likely more to be discovered. Each has its own feeding strategy, typical body type, and associated behavior. Usually more than one ecotype is found living in the same place. Take for example the continental shelf of the northeast Pacific. These nutrient rich waters are home to the kind of expansive seafood buffet usually reserved for Red Lobster and questionable casinos. Fish, birds, mammals, and invertebrates are all in ready supply if you're clever enough to harvest them. This smorgasbord has allowed for three different ecotypes to develop in one region.

Courtesy: Dahlheim et Al. (2008), Marine Mammal Science, 24(3)

The most well understood of these three types are the resident killer whales. There are three populations of resident orcas in the northeast pacific; the Alaskan Residents, the Northern Residents, and the Southern Residents. All of these groups live in fairly large pods of usually around 30 individuals. Occasionally the entire Southern Resident Community gets together for a big ol' fashion hootenanny. Seriously, this 85 whale strong "superpod" is as close to a college kegger as any species other than humans get. This is the time when the Southern Residents say hey to friends, hook up with each other, and shout across the room to orcas they know. That last one is only partly a joke. Resident orcas are the chatty Kathy's of the ecotypes. They're highly vocal because their favored prey requires them to be highly coordinated in their hunting.

Resident orcas eat nothing but fish, and about 90% of that fishy diet is salmon. Why? Because salmon meat is just drowning in oil. Those natural fats are great for preserving the whales' blubber layer, which keeps them warm. Salmon is also absolutely dense with chemical energy, and that's essential for maintaining an active body and mind. 

All orca ecotypes employ echolocation clicks to navigate their environment. But in order to effectively corral schools of speedy fish, residents employ a complex vocabulary of whistles. Their calls regularly change pitch, tone, and frequency as they communicate with one another. 

"So anyway I said to him" 'go left', and he went right, so I said: 'no, 
your left', and he said: 'What do you mean I'm left? we're all still here'" 
Courtesy: Tundra Ice via Flickr  

Resident oracs are usually the ecotype that people are most familiar with. This is mostly due to the fact the they remain in a relatively small area throughout their lives. The Southern Residents are probably the most extensively studied and photographed whales in the world. They have legions of fans, and what's not to love about residents. They're rarely far away when you need them, they're gregarious, and they eat food that we don't find particularly cuddly. Transient orcas, also called Bigg's killer whales, are an entirely different story.

Transients are the leather jacket wearing, smoking behind the gym, switchblade carrying, greasers of the ecotypes. Everyone who's ever loved a bad boy or girl can get into the transient orcas. "What makes transients the badasses of the dolphins?" I'm glad you asked.

Transient orcas are primarily mammal eaters, and they almost never touch fish. This ecotype preys upon seals, dolphins, porpoises, occasional birds, and even baleen whales! With each prey type comes a different hunting strategy. Seals are usually grabbed from below the surface and quickly killed, but in contrast, sea lions are gradually beaten to death with the tails of each pod member. Then this frequently happens:

Hahaha Okay I admit this at least a little funny.

Yup, they play with their food. Take what your average cat does to a mouse, scale them both up about 1000 times, and you have a Biggs' killer whale playing with a sea lion. But wait! It gets even more intense. Transients hunt the giant cetaceans by drowning them. I'll let the BBC and David Attenborough give you the specifics in the video below

Really intense footage, but absolutely incredible.

Although each attack type has different characteristics, what's consistent is that transients are quiet and work with a small crew. They swim in loosely defined small pods, usually no more than 10 individuals, to increase each whale's share of the prey. And since their prey hears very well, transients go into stealth mode once they've identified a target. Only once they've taken down their meal do they resume vocalizing. 

While all of his mammal killing may seem unpleasant, it actually makes a lot of sense. Since resident orcas are busy eating up all the oily fish in the nearshore, transients need another source of fat. And there's few higher quality fats than the blubber of marine mammals. By consuming different foods transients and residents can live side-by-side with little interaction and no conflict.

So if Bigg's killer whales and residents consume all the energy rich prey in the nearshore then the third ecotype must live somewhere else. 

It's on the shore isn't it? I knew this would come back to pandas.
They're like the orcas of the land!
Courtesy: fortherock via Flickr

The final of the northeast Pacific ecotypes lives in the offshore environment along the edge of the continental shelf. In one of the most creative namings ever, these offshore orcas are called... offshore orcas. Offshore's are the least well understood of the three ecotypes for a number of reasons. The main being, that the open ocean is so much bigger than the inland waters where transients and residents are usually found. It's not surprising that most of the encounters with offshores have occurred off of California where the open ocean abuts the continent.

"California whales they're so incredible. Black tail flukes, 
with blowholes on top"
Courtesy: Matthew Allen via Flickr

Genetic studies have found that offshore orcas are probably most closely related to residents. They're also similar to residents in their behavior and  general diet. Offshores appear to be fish eaters and live in very large pods, sometimes more than 100 whales strong. It's not clear if this is similar to the summer superpod that the southern residents get into once a year, or something else entirely. 

Where residents and offshores differ is in how far they'll travel, and exactly what kind of fish they eat. The same group of offshore orcas have been seen at Dutch Harbor in the Aleutian Islands, and Dana Point in California. That's 4,435km if the pod swam in a straight line, which it almost certainly didn't. In contrast the Southern Resident population only leaves the Salish Sea near Washington and British Columbia on occasion.

Courtesy: Dahlheim et Al. (2008), Marine Mammal Science 24(3)

We don't have a great idea of offshore killer whales' diets, but they seem to be less picky than residents. They've been seen attacking schools of baitfish, and beating blue sharks with their tails. They've also been found beached with salmon and halibut in their stomachs. Another piece of evidence has led some scientists to speculate that sharks are a major component of their diet. 

When offshore orcas wash up on beaches their teeth are frequently worn down almost to the gumline. Even young animals, whose teeth can't have eroded from age, show a lot of wear. Sharks have rough, sand-papery skin that could probably buff an orcas teeth down to the jaw if they eat them all the time. Offshores also have fewer tooth marks on their bodies from scrapping with other orcas, suggesting their teeth aren't very pointy for most of their lives.  

We've barely begun to scratch the surface of offshores' life history even though we've known about them since the 80's. In fact there's so much more to learn about all three ecotypes. Their behaviors and life styles are so different that they might even warrant being considered several species of orca. But for now, killer whales are a single group of highly intelligent, adaptable, long-lived, nomadic hunters, just like humans before agriculture and urbanization. Killer whales, they're like the humans of the sea!

Several ton, fish-eating, flippered, black and white, humans.
Courtesy: Putneypics via Flickr


Dahlheim, Shulman-Janiger, Black, Ternullio, Ellefrit, & Balcomb, (2008) "Eastern Temperate North Pacific Offshore Killer Whales (Orcinus orca): Occurence, Movements, and Insights into Feeding Ecology", Marine Mammal Science 24(3): 719-729, doi: 10.1111/j.1748-7692.2008.00206.x

Dahlheim & White, (2010) "Ecological Aspects of Transient Killer Whales (Orcinus orca) as Predatorsin Southeastern Alaska", Wildlife Biology 16:308-322, doi: 10.2981/09-075

Ford MJ, Hempelmann J, Hanson MB, Ayers KL, Baird RW, Emmons CK, et Al., (2015) "Estimation of a Killer Whale (Orcinus orca) Population's Diet Using Sequencing of DNA from Feces", PLoS ONE, 11(1): e0144956, doi:10.1371/journal.pone.0144956

Riesch & Deecke, (2011), "Whistle Communication in Mammal-eating Killer Whales (Orcinus orca): Further Evidence for Acoustic Divergence Between Ecotypes". Behavioral Ecology sociobiology, 65: 1377-1387, doi: 10.1007/s00265-011-1148-8

"About Killer Whales", Center for Whale Research 

No comments:

Post a Comment