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Sea Otter Savvy

Sea Otter Science And Community Outreach

Sea Otter Society: The Breakfast (Lunch, and Dinner) Club

sea otter society food

sea otter society food quarter lb 350

By Claire Mayer

What we eat turns to heat! Everyone has that one friend who lives to eat and not the other way around. The next meal is planned before the current is consumed. And while this is a choice for most humans it is not a choice for our friend the sea otter. Just to stay alive in these cold waters of the Pacific Ocean, sea otters must eat 25% of their body weight per day. If an 80 lb. sea otter ate only Quarter Pounders, he’d have to eat 80 of them every day! Can you imagine chowing down every day on three hearty breakfasts, four lunches, two dinners and then a midnight snack or two? While it may sound glorious to some it would surely require a lot of meal prep!  For sea otters the work is in the foraging ─ the finding and processing of prey.

Being the only marine mammal lacking a thick layer of blubber, sea otters rely on their high metabolism and dense fur to stay warm in a cold ocean. Because the calories they eat are converted to heat this helps maintain their high body temperature (roughly 100 degrees Fahrenheit). To generate the number of calories necessary to fuel the sea otter’s “heat engine” equates to one thing…eating, eating and more eating.

Sea otter biting into the anti-predator defense system of an urchinOuch! A sea otter biting into the anti-predator defense system of an urchin. Photo by Joan TisdaleWhat most don’t know is that finding so much food means very hard work for the sea otter. Not only is it extremely time consuming (in some parts of their range they may spend half of a 24-hour day foraging), but their various foods (aka prey items), have evolved an array of defenses to AVOID being eaten! For prey it pays to be difficult to locate and tough to open. Just what does the average sea otter go through to get a good day’s meal? Try dives to the bottom while holding their breath and kicking against the buoyancy of their fur’s air layer to dig for clams and worms, or patiently prying abalone and clumps of mussels from their rocks along the shore. An abalone meal may require 10 or more dives (and a rock tool) to pry loose. A sea otter can often be seen wrestling a prickly urchin or an angry crab aboard its chest while a stealthy gull stands by waiting for scraps. A sea otter specializing in small marine snails must stuff her underarm pockets full and pulverize each snail on a rock anvil. The struggle is real for the sea otter when it comes to finding food, but find food they must ─ just a few days without sufficient food can mean starvation. Not only does foraging take great effort, but their meal can pinch back (no thanks!) All this eating not only feeds the sea otter but keeps numbers of herbivores like urchins under control helping the kelp forest to thrive.

So the next time you see a sea otter devouring a tasty morsel be happy for the successful forage attempt. Maybe take a moment to appreciate all the hard work, time and energy that went into that dive, pry or dig in the sand. Be mindful too of the endless food choices within our arms' reach at the grocery store as compared to the limited options available to a sea otter foraging for their survivial or that of their offspring. Just as we don’t like our own precious mealtimes being interrupted let those sea otters dine in peace. As they finish that meal, they will already be thinking about the next! 

About guest blogger Claire Mayer: Claire was born and raised in Monterey, California. She is a former animal care volunteer with the Monterey Bay Aquarium's Sea Otter Research and Conservation program. She currently works as a Veterinary Assistant in Carmel, California. 

Read about the science of sea otter foraging:

Individual variation in prey selection by sea otters, 2003.pdf

Food limitation leads to behavioral diversification, 2008.pdf

Sea Otters on the Island of Blue Dolphins, Part 3

Sea otter eating a turban snail. Photo by Erin RechsteinerSea otter eating a turban snail. Photo by Erin Rechsteiner

By Gena Bentall

Read Part 1 and Part 2 of this series

sni 3 megastaea split 350The wavy turban snail, Megastraea undosaPerched on a rocky bluff overlooking the jumbled boulder beach called Rock Crusher on San Nicolas Island, my eye rests steadily on the eyepiece of my Questar telescope, the instrument of choice for sea otter spotters for decades.By the end of the day, I will have a solid red ring the size and shape of the rubber eyecup around my right eye. A female sea otter pops up from a dive, and I quickly click my stopwatch, “Dive time, 35 (seconds)”, I say to my colleague, USGS biologist Joe Tomoleoni, who is recording data at my side.  I flip the scope to high power to zoom in on her prey. With slow gusto, she is hammering a pyramid shaped object on a flat rock on her belly. She rolls over, and the rock is gone, likely stashed in her underarm pocket of loose skin. She now shakes the object like a salt shaker and bites at its base. “She has a wavy turban,” I say, “and she’s shaking it!” Wavy turban snails (Megastaea undosa) are a large marine snail abundant in the kelp forests surrounding the island we call San Nic. She cracks the hard shell on the rock, then shakes the snail out of its fractured home. “It’s a size 2b!” I exclaim, using a handy measuring tool, the mean width of a sea otter’s paw, to estimate size. The female sea otter works on the prey for a minute or so, handing a few bits to her pup who swims over to solicit handouts. Then she dives to search again, “Surface time, one minute, 50 seconds”. This process of watching sea otters dive, forage and eat has been carried out for tens of thousands of dives across decades of study in California. It is the foundation of our understanding of sea otter foraging ecology and their important place in the complex food web of coastal California. For some tagged sea otters along the Monterey Peninsula, the detailed statistics of their forging behavior have been documented for a decade or more, providing an index for exploring how each individual sea otter fits into the complex and dynamic coastal food web.

Research diver records species complexity at San Nicolas Island. Photo by Zach RandellResearch diver records species complexity at San Nicolas Island. Photo by Zach RandellThe coastal ecosystems of California do not exist in a static state. They are continuously influenced by a myriad of factors —climate, disease, fishing, pollution —to name just a few. A change in the abundance of one species may have far ranging effects, with the influence of some, the keystone species, packing a greater punch than others (check out this video). San Nicolas Island is a ideal microcosm in which to study the "sea otter effect" on a California kelp ecosystem. As the resident sea otters of San Nic have grown in number since the translocation project of the late 80s, observations of their foraging behavior help scientists understand how sea otters adapt their diet as their density and distribution around the island changes. Complimentary long-term work by scientists studying the species composition at both sub-tidal and intertidal sites around San Nic, documents how those communities change in response to a suite of factors. These long-term studies were started before the first sea otters were translocated to San Nic with the goal of documenting changes in species abundance as the predators re-established and grew in number. Definitive understanding of the factors influencing the kelp forest ecosystem surrounding the island, however, has proved elusive, with a clear “sea otter effect” muted by the effects of disease and changing climate.   When asked about the challenges of studying such a complex ecosystem, Joe Tomoleoni (who, in addition to being a shore-based biologist is also a diver who has worked on the subtidal San Nic team) reflected, “It’s hard enough to figure out California’s kelp forests in a static state, but with so many variables—temperature, currents, disease, harmful algal blooms, primary productivity, fishing, ocean acidification, etc.—all changing all the time, things get pretty messy in a hurry. These communities have lots of moving parts.  Determining a sea otter effect is difficult because we aren’t able to design an experiment that accounts for all possible variables.  We are left simply observing change and using correlations to piece the puzzle together."

San Nicolas Island, Channel Islands, CaliforniaSan Nicolas Island, Channel Islands, CaliforniaAfter observing our focal forager for 20 consecutive dives (no small feat with an untagged sea otter on a rugged shore), Joe and I scan the kelp bed for the characteristic backstroke attitude of a new foraging sea otter. The team’s bouts of foraging data collection are peppered among our sea otter survey forays, and this expedition has revealed some exciting changes in how San Nic’s sea otters are inhabiting the island. While the kelp beds of places like Rock Crusher on the southwest end of the island still harbor a fair number of sea otters, on this trip our team spotted the highest numbers ever on the north side, an area that has remained largely uninhabited since the translocation. We find the offshore reef known as The Boilers (see Part 2 of this series) is largely devoid of both kelp surface canopy and sea otters. As sea otters are known to do, perhaps they have abandoned the long-occupied Boilers in favor of possibly richer food supplies along the north shore. By shifting habitat use in this way, sea otters may allow prey at long-occupied places to rebound in a sea otter’s version of crop rotation.

 A San Nic foraging team collects foraging data on the north shoreA San Nic foraging team collects foraging data on the north shoreAs the sea otters of San Nic explore, so must scientists follow and the team scrambles to find new observation perches. Even after decades of watching sea otters forage, I still feel an incomparable giddiness as I await the first prey captures at a new location for my favorite sea otters on the planet. Through my Questar I can see a burst of tiny bubbles (air pushed from the fur by the pressure of water) that marks the location of a diving sea otter. As I fix on the location, the head of a sea otter bursts through the surface, and she immediately assuming the belly-up dining posture unique to her species. “She’s up,” I call out, “Success is yes—HOLY COW!”

 Stay tuned for part 4 of our series on the sea otters of San Nicolas Island...

 

The author: Gena Bentall has been studying sea otters since 2001. For her graduate thesis she studied the sea otters of San Nicolas Island. She is now the Program Coordinator of Sea Otter Savvy.

sni kelpA lush giant kelp bed at San Nicolas Island. Photo by Zach Randell

Sea Otter Society: The Single Moms' Club

moms us grid

The Single Moms' Club: A pup a year deserves a cheer!

by Claire Mayer and Gena Bentall

It is no big secret that parenting is a full-time job. Imagine having one baby a year until the day you die! Such is the life of our devoted sea otter mothers. Not only do they give birth (on average) to one pup each year, but they will have and rear pups into their senior years! Along with mothering multiple pups throughout their lifetimes, sea otter moms do it single-handedly. They are truly “single mothers”, with no child support or help with pup-rearing from dad. After courtship and mating, males are out of the picture and mom is the sole provider of six months of constant pup care. No nannies, babysitters, or grandparents will share the load with these moms.

Mother sea otter will give birth at sea and then be a 24/7 caregiver for her new offspring as he or she transforms, over the next 6-8 months, from a helpless bundle of fur into a young sea otter ready to make it alone in the ocean. Her body will make rich milk to nurse her growing pup, and when the pup is just a few weeks old, she will share her prey, teaching her pup what’s good to eat and how to eat it. As any parent can relate, these months of dependency can be physically taxing, and sea otter moms will be pushed to their survival limits by the time their pup becomes independent. Every year her reproductive cycle replays ─ estrus, pregnancy, birth, pup rearing, weaning, estrus ─ until her death. She will give her all to launch successful, independent sea otters into the world.

moms kayaksKayakers approaching too close to sea otter moms with pups can cost them energy they can't afford to lose! Give them space! Just like many in human society, an individual’s status as a parent may not be obvious at a glance.  The sea otter you spot swimming by your kayak or sleeping deeply in a kelp bed could well be in the Single Moms' Club. She could be caring for a dependent pup or pregnant with her next pup (it’s hard to see her baby bump). She could also be in estrus (the scientific term for “heat”) and contending with persistent male suitors while she’s trying to find the food she needs to stay alive.

Just as we respect the demands of the all mothers within our own society, keeping our distance allows these sea otter moms to perform their important job of bringing new sea otters into the world. Next time you see a wild sea otter, think of the mothers! Rather than approaching that single mom for a selfie we suggest appreciating all that she is and does from afar. Be a hero to the next sea otter you meet, and respect their well-earned nap!

When do sea otter pups try solid food?

When do sea otter pups try solid food?

Sea otter moms start offering solid food to their pups at just a few weeks of age. Pups first learn about foraging from their moms--what critters to eat, how to find them, and how to handle spines, hard shells, and pinchers. By the time her pup is ready to become independnet, she will be handing over as much as 1/3 of her prey to her growing pup!
How long will a female sea otter continue to have pups?

How long will a female sea otter continue to have pups?

Sea otter females do not experience reproductive senescence and will have pups every year throughout their 15-20 year lifespan.
How long do sea otters nurse their pups?

How long do sea otters nurse their pups?

Mother sea otter will nurse her pup right up until the day they are weaned, usually around 6 month of age! It takes a lot of energy to produce this rich milk.

Thanks to Joe Tomoleoni (Eco Exposure Photography), Nicole LaRoche, and Sea Otter Savvy volunteer Joan Tisdale for contributing photographs!

Sea Otter Conservation Workshop: Highlights

 

Dr. James Estes gives the keynote address at the Seattle Aquarium's Sea Otter Conservation Workshop XIDr. James Estes gives the keynote address at the Seattle Aquarium's Sea Otter Conservation Workshop XI

Sea Otter Conservation Workshop XI    Seattle Aquarium   March 29-31, 2019

By Gena Bentall

The biennial Sea Otter Conservation Workshop, hosted by the Seattle Aquarium, has become the hottest scene for biologists, zookeepers and aquarists, advocates, and government specialists working with or interested in sea otters.

This year, the seats were filled each of the three days of the workshop with attendees eager to hear the latest information on sea otter ecology, conservation, physiology, husbandry, population status, genetics, and veterinary themes. In the evening, guests were treated to a dinner with a Window on Washington Waters and a view of the sea life of Puget Sound as a backdrop. The keynote address was delivered by the esteemed Dr. James Estes who spoke about the last 50 Years of Sea Otters and Coastal Ecosystems: History and Highpoints.

Over three days, with more than 50 speakers from California to Japan, there was something for even the most seasoned sea otter biologist to learn. Sea Otter Savvy was represented by two talks, one by Moss Landing Marine Laboratories' graduate student, Heather Barrett, who summarized the results of her project Investigating the energetic cost of anthropogenic disturbance on the southern sea otter, which is based on data collected by our citizen science team. During the Conservation session, I summarizing the Sea Otter Savvy program accomplishments. There were many exceptional talks, but here are my top 5 in no particular order:

Map of Hokkaido, Japan showing locations of sea otter sightings from Hattori et al, 2005Map of Hokkaido, Japan showing locations of sea otter sightings from Hattori et al, 20051. The return of sea otters along the coast of eastern Hokkaido, Japan.

It was great to hear an update on the little studied sea otters of Japan. Yoko Mitani, of the Field Science Center for Northern Biosphere, Hokkaido University, shared the newest information about the distribution and foraging behavior of sea otters off Hokkaido’s eastern coast. This small pollution is expected to expand, and Yoko predicted conflicts with local fisheries as is consistent with most sea otter recovery stories.

 

 

Brown bear feeding on a sea otter at Katmai National Park. Trail cam photo courtesy Dan Monson and the National Park ServiceBrown bear feeding on a sea otter at Katmai National Park. Trail cam photo courtesy Dan Monson and the National Park Service

 

2. Top-level carnivores linked across the marine/terrestrial interface: sea otter haul-outs offer a unique foraging opportunity to brown bears.

Until I heard this talk by long-time Alaska sea otter biologist, Dan Monson, of the U.S. Geological Survey, Alaska Science Center in Anchorage, I had no idea that brown bears were predators of sea otters! Dan showed us some amazing trail-cam photos showing brown bears stalking and killing hauled out sea otters (and harbor seals) in the Katmai National Park and Preserve in Alaska. While sea otters are voracious predators, they are not always at the top of the food chain!

 

The keystone predator paradigm of sea otters, kelp, and urchins was formed based on observations in Alaska. Moving south into california, a more temperate region, the sea otter keystone predator paradigm becomes more complex because of additional contributors to the ecosystem and their expanded role in warmer waters. Graphic courtesy S. Lyon, USGSThe keystone predator paradigm of sea otters, kelp, and urchins was formed based on observations in Alaska. Moving south into california, a more temperate region, the sea otter keystone predator paradigm becomes more complex because of additional contributors to the ecosystem and their expanded role in warmer waters. Graphic courtesy S. Lyon, USGS3. Revisiting the role of southern sea otters in California kelp forest.

I had been eagerly awaiting this talk by Sophia Lyon, of the U.S. Geological Survey, Western Ecological Research Center, Santa Cruz Field Station in anticipation of getting a sneak peak at early returns on the large-scale, multi-faceted NSF study looking at interactions between sea otters, urchins and kelp forests in the wake of the sea star die-off due to wasting disease. Long-story short: California kelp ecosystems are complex, with an array of species filling each functional role. The loss of the urchin-eating sea star, Pychnopodia, from large areas of the west coast, while devastating, has taught ecologists much about the teamwork of kelp forest predators, and there is still much to learn and discover. Sea otters are still important players in the game, but they are one on a team of all-stars keeping the kelp forest stable, diverse, and healthy.

Future sea otter tags will share data with researchers via a wireless gateway. Graphic courtesy USGSFuture sea otter tags will share data with researchers via a wireless gateway. Graphic courtesy USGS

4. New tagging technology for sea otter research: an update on OtterNet.

The direction of research and development of new sea otter tagging technology aims to minimize impact to sea otters while also maximizing the efficiency of data collection. Engineers at NASA have teamed up with USGS and the Monterey Bay Aquarium to create flipper tag tech so super-secret, I cannot share pictures of the tags (or I’d have to kill you). Joseph Tomoleoni, from the U.S. Geological Survey, Western Ecological Research Center, Santa Cruz Field Station, was able to share how these “smart” tags would collect novel and improved data, while also being affordable and less intrusive to sea otters. When I said, “Give sea otters space”, NASA answered the call!

Researchers from Apex Predators, Ecosystems, and Communities (APECS) collect data in a SE Alaska eelgrass bed. Photo by Nicole LaRocheResearchers from Apex Predators, Ecosystems, and Communities (APECS) collect data in a SE Alaska eelgrass bed. Photo by Nicole LaRoche5. The complex role of sea otters in southeast Alaska.

Ginny Eckert, from the University of Alaska Fairbanks, described the complex interactions of sea otters, coastal ecosystems, and fisheries in a place where the sea otter population has recovered to over 25,000 animals. This is a story nearing its climax, with the economic interests of humans coming face to face with the recovery of an ecological superpower, one who had been eliminated from southeast Alaska by another economic endeavor---the maritime fur trade. Sea otter effects on the productive and carbon-sequestering eelgrass beds of SE Alaska are currently described as mixed and complex, and this talk left me wondering and wishing for the chance to give this system time to find its sweet spot with the return of a predator that fed near its shores for millennia.

 

For those who aspire to reach the upper tiers of sea otter savviness, there were many more interesting talks. You can view the proceedings and read the abstracts here.

Hattori, K., Kawabe, I., Mizuno, A.W., Ohtaishi, N. (2005). History and status of sea otters, Enhydra lutris along the coast of Hokkaido, Japan. Mammalogical Society of Japan, Mammal Study 30: 41-51.

 

Gena Bentall is the founder and Program Coordinator of Sea Otter Savvy and has been a sea otter biologist since 2001.