MIGRATE (of animal) (v)-to move seasonally from one area to another
Background
Scientists know that when summer sea ice in the Arctic melts away from their shallow feeding grounds, Pacific walrus will haul out on land to stay near their food. The Icy Cape stampede showed scientists that land haulouts in the Chukchi Sea can be dangerous for young walrus. Scientists wonder how walrus populations will be impacted when the walrus have to use land haul outs more and more often. To understand how walrus populations might be affected by changes in their Arctic habitat, scientists first had to understand "normal" Pacific walrus behavior.
Take a look at the videos and fact sheet below to explore what researchers already know about the mysterious Pacific walrus.
VIDEO: The Pacific Walrus
Understanding walruses' relationship with sea ice is important to understanding their behavior. (1 minute)
Pacific walrus feed in relatively shallow water, hunting for small invertebrates on the ocean floor. In the Bering and Chukchi Seas, the continental shelf provides a vast area of shallow, rich feeding grounds for the walrus.
Walrus haul out on sea ice or on land to rest between feeding trips. Although they are good swimmers, they don’t typically swim long distances, so they prefer to rest near where they eat.
In the winter, arctic sea ice extends south into the Bering Sea, where large herds of male and female walrus spend the winter together. Then in the springtime, females and calves follow the melting sea ice north into the Chukchi Sea, while adult males separate from the rest of the population and migrate south to spend the summer in Bristol Bay.
The male walruses in Bristol Bay typically haul out on land and feed near shore. In the Chukchi Sea, the females and calves spend their summer floating on the sea ice, drifting over the shallow continental shelf.
In recent years, summer sea ice in the Arctic has melted beyond the edge of the continental shelf, leaving the females and calves without their traditional feeding and resting platforms.
Female walrus and their calves use sea ice all year. They migrate to the Chukchi sea in summer because there is so much food available for them there. Watch the video below to hear Dr. Lori Polasek talk more about how females and calves may be affected if they can't haul out on sea ice and must move to areas on land, instead.
VIDEO: Females and Calves
Dr. Lori Polasek describes how females and calves might be impacted by hauling out on land instead of sea ice. (1.5 minutes)
What are some of the possible impacts of females and calves hauling out on land instead of sea ice?
There are several important facts about walrus that we had to understand before starting this project, and one of those is that land haulouts are primarily used by male walruses, of all ages, and ice is primarily used by females and calves. And the importance of ice, you can think of it as a mom and calf are floating around on a piece of ice and that keeps them moving across the water so it allows them to utilize different resources so they don’t impact a resource and completely deplenish [deplete] it. Also, by allowing them to float around, they’re not congregated together, where they’re more susceptible to predators, where then you allow the whole herd’s offspring to potentially be wiped out by a predator. It also takes your young, your offspring which are more susceptible to disease, and separates them from the population so that disease can’t spread as fast.
So these new emerging haulouts with moms & calves packed together, then wipe out all of those protections of those calves by exposing them to disease as a group, by allowing them higher exposure to predators, and then by also having them together totally deplete resources in a localized area.
Arctic sea ice extent is impacted by changes in seasonal and global climate. Walrus respond to changes in sea ice by migrating and adapting their behavior. Understanding how sea ice forms and why it melts can help scientists understand more specifically how walrus will be influenced. Check out the sea ice fact sheet below!