Four more sleeps until Polar: Wildlife at the Ends of the Earth lands in a bookstore near you!
During preliminary research for the book, when I was trying to figure out which adaptations I would cover and which animal from the Arctic would be paired with each animal from the Antarctic, I came across a weird fact about walruses that totally tickled me – until I realized there was no place for it in the book. Fortunately, there is always room for weird facts on this blog! So let’s take a look at feeding behaviours of Atlantic walruses. Specifically, those in Young Sound, off of North East Greenland.
What Do Walruses Eat?
Walruses are benthic feeders, meaning they forage for food on the bottom of the ocean. They love bivalves – molluscs such as clams that have hinged shells – and there are three specific species that they will choose when given the chance.
Like all marine mammals, walruses breath air, and they can only stay underwater for about 10 minutes before they need to take another breath. So they usually forage in mollusc beds that are between 1-6 m below the surface. Short travel time means they can maximize feeding time before swimming back to the surface.
And it takes a lot of molluscs to feed a walrus. One study found the remains of 6400 molluscs in a single walrus stomach! A male walrus that weighs 1226 kg eats about 74 kg of mollusc tissue per day. They spend 13 to 14 hours out of every 24 searching for food.
How Do Walruses Hunt?
Scuba diving scientists hung out in the water, filming walruses as they fed. The ocean bottom of Young Sound is sandy, and feeding stirred up a lot of sediment, so scientists couldn’t tell exactly how the walruses were getting molluscs out of their shells. But they did get great views of how walruses go about finding prey that can be buried up to 40 cm deep.
And they shared the videos! For copyright reasons I can’t embed them here, but the videos are available online for free. Hop on over to the webpage for the original research article. In the right-hand menu, click on Electronic Supplementary Material. You can download the files and play them on your computer as often as you want.
Speaking of right-hand… but I’m getting ahead of myself.
According to the study, walruses dive to the mollusc bed and settle with “their tusks resting like a sledge on the bottom.” Wear marks caused by dragging their tusks along the sand were clearly visible when the walruses were hauled out on shore!
Walruses face into the ocean current, so that the moving water pulls stirred-up sand away from their eyes. They appear to be looking for food with their eyes, as well as feeling for it with their whiskers. And they use three strategies for locating tasty niblets:
- Using the whiskers on their snouts to feel for buried food
- Squirting a water jet from their mouths to blast away sand
- Waving a flipper over the seabed to sweep away sand
The waving method is the most popular. And – apologies to any human lefties out there – walruses are right-handed! They wave with their right flippers 89% of the time. No single walrus preferred to use its left flipper. Granted, this was a small study of only a handful (ha!) of walruses, so it’s possible the lefties are out there. But either way, the very notion that walruses might have a “hand preference” just as humans do strikes me as just the most delightful thing.
How Is Climate Change Affecting Walruses?
While a little less weird than the handedness fact, this is also really, really interesting. Because it actually depends.
For the North East Greenland walruses, warming climates might be a good thing. That’s because, in the winter, the shallow water where walruses feed is actually frozen right to the ocean floor. This “fast ice” forces the walruses to winter on offshore sea ice, where the ocean bottom can be as much as 200 m down. Longer travel times mean less time to feed at the bottom before running out of air.
Right now, the coastal feeding grounds are available to walruses between the end of July and October, when the water re-freezes. Climate change means that the open-water period is getting longer, and open water seems to be good for food production in the area. So it’s possible that the North East Greenland walruses, a small population that currently numbers about 1000, might actually increase – at least for a while.
It’s a different story for Pacific walruses, like those shown it the picture. Female walruses raise their young near the edge of the summer sea ice, which used to give them a place to rest with good access to shallow water feeding grounds. In recent years, however, there’s been more summer melting, meaning that the ice edge is retreating farther from shore. That puts the mamas over deeper water, making it harder for them to find food for themselves and for making milk for their young. For walruses in this type of habitat, loss of summer sea ice could become a major threat.
If you want to led the walruses a helping hand (I’m sorry, the puns, they write themselves), stay tuned. On May 2 – release day! – I’ll be posting a resource list that includes information on climate change and ways that we can help. In the meantime, keep doing all the things you are already doing to make our world a better place for humans and for polar wildlife.
Polar: Wildlife At the Ends of the Earth comes out in 4 more sleeps! EEK! Pre-order a copy from your local independent bookstore to reduce your carbon footprint AND support a cornerstone of your community.
Don’t forget to check my Public Appearances page for Polar virtual events and live events happening near you! Are you a teacher or librarian? I’m available for author visits in May and June – contact me to secure your spot.