Much like cattle within the continental United States, walrus are a staple for Native Alaskans’ livelihood, be it hides for clothing, meat for food, grease for cooking and ivory for tools and scrimshaw for trade.

The Pacific walrus is the only subspecies of the mammal to inhabit U.S. waters. Native Alaskans rely on its bountiful population for the state’s economy and cultural subsistence; walrus is so vital, in fact, that a stable animal population is crucial to Native Alaskans’ survival and way of life

Enter NASA, who – in collaboration with the Department of Interior’s U.S. Fish and Wildlife Service (USFWS) – has taken to using satellite imagery to study the migration and habitat of Pacific walrus in the icy climes of the Bering and Chukchi seas.

Walrus live on Arctic pack ice, the dirty, wind-driven rills and flats of which vary in color, thickness, and landscape.

Commonly reaching proportions of 12 feet in length and 3,000 pounds, a walrus seeks an ice floe of sufficient density and surface area to support its "hauling out" to rest, mate and rear its young, yet still thin enough to break through to escape a polar bear, its natural predator.

Such a dynamic nature to the ice and its appearance pose unique challenges to remote-sensing studies. Add the abbreviated diurnal cycle of the Alaskan fall and winter, and researchers can literally find themselves in the dark while searching for walrus.

To study the population dynamics and supporting habitats of the Pacific walrus, students from the NASA Develop program worked with the U.S. Fish and Wildlife Service in the state to determine the relationship between polar sea ice formations and the movements of the Pacific walrus. For the first time, radar sensors were used to study the walrus in the Alaskan Yukon-Kuskokwim Delta.

The largest census ever conducted for the walrus population was undertaken last winter and spring, according to Jay Skiles, senior research scientist in biosphere science at NASA Ames Research Center in California.

"The count took almost two months," he recalled, and required the use of boats, ships – including a Russian icebreaker – airplanes and helicopters with thermal sensors.

NASA’s Develop program encourages teams of selected high-school students to examine NASA science research results and observations deemed relevant to societal concerns, in order to perform advanced, analytical experiments to demonstrate a contribution to national policy and decision-making.

During the USFWS survey, a low-flying aircraft with a thermal sensor onboard scanned for thermal signatures, or walrus. Since walrus are warmer than the ice surrounding them, each point on the flight path, or scanline, represented their presence. Satellite imagery supplemented the airborne thermal data to classify three ice types (thick, medium and thin). The flight-path imagery was overlaid upon satellite imagery from the same region and general time period.

Results of the analysis from the synthetic aperture radar (SAR) data suggests that walrus prefer regions composed almost entirely of medium thickness; specifically, first-year ice of approximate thickness between 70 and 120 cm (2 to 4 feet).

While Skiles said the study was "by no means exhaustive," he added "our data suggest the possibility that sea ice features may be critical factors for the walrus when choosing a habitat. Using techniques developed during this project, the U.S. Fish and Wildlife Service may be able to determine, over time, if climate change is affecting Pacific walrus populations" so necessary to Native Alaskans.