When people think about otters they picture a cute, fuzzy animal frolicking in the water, floating on their backs just chillin’, or banging away at a sea urchin on their bellies (or maybe I’ve just been watching too much Discovery channel). The otter that people have in mind is Enhydra lutris, commonly known as sea otters.
Sea otters are a marine mammal, like seals, but do not have thick layers of blubber to keep them warm. Instead, sea otters are covered in a double-layer of fur; the bottom layer is short and extremely dense, the top layer is longer and waterproof. These two fur layers work like one of those puffy winter jackets; the outer (top) layer keeps the inside dry and the inner layer (the puff) captures body heat to insulate the otter. Fur can’t do all the work though; otters still lose a lot more heat than their blubber-covered friends, so to keep up their body temperature otters have to eat a LOT! According to The Otter Project, to keep their metabolism and body temperature up otters have to eat the equivalent of 20-30% of their body weight per day. That’s like me (120lb shortie) eating 36 pounds of food a day, aka 36 boxes of spaghetti every single day! And otters don’t have the luxury of a supermarket or grocery store; they have to hunt for all of their food so they’ve gotten pretty creative.
Otters are among a small group of animals who use tools (humans included). They use other shellfish, rocks, and a little help from us (man-made objects they may find) to crack open their food and they have pit-pockets for storage! Loose skin under their front legs creates a sort of pocket that otters use to hold tools or prey while it works to get some more snacks. Common otter-entrées include sea urchins, clams, mussels, crabs, marine snails, and abalone. All of these foods are hard nuts to crack, but otters are well-equipped to handle these tough cookies. Using teeth and tools, otters break open prey with strong crushing molars and canines or pound them open on their chests.
So what’s cuter than a sea otter? A sea otter pup of course!
Female otters are some hard-working mammas. First of all, they don’t get any help from the dads. Males have multiple mates and are more concerned with patrolling their territory than being the ideal dad. So it’s up to the females to feed and raise their pup; which is why they have only one pup (twins are rare and it is too hard for a female to raise both pups, unfortunately she has to pick one or they will all die). Pups are born year-round with peaks between May and June (northern populations) and January and March (southern populations) and weigh about 5 pounds. They are sooo fluffy that they can’t dive underwater, so they spend their days getting groomed and bobbing around in kelp cradles while their mom’s hunt (sea otters wrap themselves in kelp to keep from floating away when they rest). The good-life lasts for about two months, then survival lessons start, and at 6 months to a year old the pup is weaned and set loose in the world…
The ‘world’ to a sea otter is near the coast along the northern Pacific Rim; from California to Alaska and across the Aleutian Islands to Russia and Japan. Sea otters used to be abundant throughout this range, with historical population numbers between 150,000 and 300,000 individuals. Unfortunately, Russian explorers discovered otter’s oh-so-fluffy fur and hunted them to near extinction. The fur trade dropped the sea otter population from hundreds of thousands of otters to just two thousand otters worldwide; that means hunters killed 99% of all sea otters in the entire world. Wow. Since the end of the fur trade, sea otter populations are slowly recovering; 2007 population estimates 100,000 sea otters worldwide. That’s much better, but otters are still an endangered species and there are a lot of factors that are preventing sea otter recovery.
Three main challenges that sea otters face are oil spills, predation by killer whales, and us. I have talked about the sea otter’s duel-layered fur, top = waterproof and bottom = warmth. Oil spills strip the otter’s top layer of fur, which means it is no longer waterproof and the bottom layer gets wet. When the bottom layer is wet it can’t trap air close to the otter’s body to keep it warm and the otter can get pneumonia or hypothermia and die. Additionally, the otter may ingest oil while trying to clean itself which can damage its lungs, liver, and kidneys. Another threat is killer whales (or orcas). Humans have killed off orca’s preferred prey, seals; so they have to eat something, right? And that’s otters. Humans have also butted heads with otters directly. Now that sea otter populations are recovering there is competition between otters and humans for shellfish. Several human fisheries are based on popular otter prey items (Abalones are one) and humans have the advantage. Otters can get caught in fishing gear and drown, and humans have more tools to fish with and more places to fish. Fishermen complain that otters are reducing prey populations, but maybe it’s our fault. Humans aren’t known for their excellent use of resources. Either way, scientists have shown that the return of otters has important positive effects on the ecosystems in which they live; they are a keystone species after all.
And since I can’t get enough of them, here are some of the photogenic cuties: