Hank: It may not seem like it while watching your dog fail over and over again to get even close to catching a squirrel, but that creature is related to an apex predator - not the squirrel, the dog. Your dog!

Wherever they go, wolves tend to sit atop the proverbial food web. But while wolves are amazing hunters, they’re still land-based animals. Except for one region in Alaska, where wolves have become the apex predators of a *marine* ecosystem.

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In 2013, a small population of Alaskan gray wolves doggy paddled its way out to Pleasant Island, just outside the border of Glacier Bay National Park. And once they got there, they saw a bunch of yummy looking deer that may have never even seen a wolf before, and they got to chowing down. In fact, they chowed down so much that they nearly wiped out their new food source. But this sudden lack of food did not make the Pleasant Island wolf population starve to death, nor did they abandon their new home and swim off to find more deer-filled forests.

No, they found another tasty treat to fill their bellies. Something a lot smaller than a deer and a lot wetter. Sea otters. They started eating sea otters. Who wouldn’t want to gobble them up, right? But actually, don’t let their appearance fool you; sea otters are apex predators in their own right. Specifically, sea otters rule the nearshore ecosystem, which is the marine ecosystem that exists close to the coastline. A sea otter’s food of choice is the sea urchin, and that’s great for the local ecosystem, because sea urchins are voracious kelp eaters.

Kelp forests are biodiversity hotspots, so if the otters aren’t there to eat the sea urchins, then the entire ecosystem will eventually come crashing down. You can actually see a similar effect when wolves aren’t there to manage a deer population. For example, when wolves were killed off in Yellowstone National Park, the local deer did too much grazing. And that caused the beaver population to plummet because they lost resources they needed to survive in winter. Yes, beaver and kelp don’t fulfill the exact same role in their respective ecosystems, but the dams beavers build *do* help maintain the local populations of fish and birds, and those populations came back not long after wolves were reintroduced to Yellowstone. So by sitting at the top of the food web, both wolves and sea otters keep everything hunky dory. And it’s why each of those species has been reintroduced to some of their old stomping grounds to try and bring some balance back to the Force – I mean the environment.

While wolves have never been classified as “endangered” in Alaska, sea otters were nearly wiped out from the entire North Pacific, due to a combination of pollution and hunting. But in the 1960s, a group was transplanted from the Aleutian Islands to the edge of Glacier Bay National Park. The transplant was a huge success. The local sea otter population exploded and spread, and by the 2000s, some had set up shop on Pleasant Island… Just in time to repopulate the coast for some very hungry wolves to stumble upon.

Now, wolves and sea otters likely coexisted in the past, but because sea otter populations have been in decline for so long, we’d never actually observed what happens when wolves and sea otters interact. And now, Glacier Bay is the *only* region in the entire world where we know wolf and sea otter ranges overlap, which means researchers have a unique opportunity to study what happens when two apex predators meet. And at least in this case, you wind up with *one* apex predator again. You also end up with a terrestrial mammal sitting at the top of a *marine* food web.

Since you don’t want the coastline overrun with kelp, you do need some sea urchins to eat it. Which means the sea otter population can’t run completely amuck like the newcomer wolves did with the Pleasant Island deer. So maybe these wolves will help the reintroduced sea otter population from ballooning too much.

But before you ask if the otters will soon go the way of the deer, thankfully, no. There isn’t much concern that these wolves will wipe out the local sea otter population. Researchers have calculated that the wolves need to eat 90 adult sea otters a year to maintain their population, and while not every sea otter in this region lives around Pleasant Island, there are still about 8,000 of them to choose from. So for now, that is enough to sustain them.

Now it makes sense that Pleasant Island’s wolves started hunting sea otters to fill the gaps in their diet, catching them whenever they would come ashore. Once I finish the charcuterie board, I will move on to other options. But what’s a bit startling is just how *fast* this all happened. In 2015 and 2016, deer made up close to 90% of  Pleasant Island wolves’ diet, but this crashed to less than one percent in 2017. While this fraction has recovered a little bit as deer populations bounce back, it still hasn’t gotten much higher than 10%. And scientists don’t know exactly why. Maybe otters are just super tasty? I've never tried otter, I don't know; I'm also not a gigantic dog, so I wouldn't know what otters taste like to them.

Maybe wolves are just reviving an ancient relationship between the species, one that we were never able to observe because by the time we started caring about predator and prey dynamics, we’d already driven all the sea otters away. Whatever the reason turns out to be, researchers did find that the Pleasant Island wolves weren’t leaving the island to hunt for other prey, so they seemed pretty content with their otter-based diet.

In fact, researchers think that if the supply of otters remains sustainable, the island wolves could stick around for a long time instead of vanishing like other packs do when the deer run out. The Pleasant Island wolves have not only been surviving, they have had cubs. So at least for now, they seem to be thriving.

And you know who’s also thriving? My neighbor’s dog, despite the fact that he has never - and will never - catch that squirrel. But you keep trying, buddy. You’re doing great.

And you know who’s also thriving? All of our patrons, without whom we could not make videos like this one about otter-eating wolves. Or, you know, slightly more adorable topics which you can check out as soon as I finish saying thanks. In exchange for keeping the lights on around here, patrons get some pretty nice perks. Like access to some bonus SciShow content, our exclusive discord, and more!

Head on over to Patreon.com/SciShow to check all the possible perks, and thanks for watching this episode of SciShow.

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