A mass of thousands of walruses were spotted hauled up on land in northwest Alaska during NOAA aerial surveys earlier this week. An estimated 35,000 occupied a single beach – a record number illustrating a trend in an unnatural behavior scientists say is due to global warming.
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Walruses (Odobenus rosmarus)—iconic arctic mammals that are only distantly related to seals—traditionally use sea ice to rest, breed, and give birth, and as a vantage from which to spot mollusks and other food sources. However, as their habitat warms and sea ice melts, walruses are forced to come to land more often and in greater numbers.
This latest mass of walruses was found during NOAA’s annual arctic marine mammal aerial survey. Previous surveys also found large groups, with 30,000 spotted in 2011. The behavior is something of a new trend, with the first large-scale land haulout observed in 2007 near where the walruses congregated last week.
"Large walrus haulouts along the Alaskan coasts in the northeastern Chukchi Sea are a relatively new phenomenon," Megan Ferguson, marine mammal scientist with NOAA Fisheries, said in a 2013 statement.
Little is known scientifically about walrus populations and the health of the species in the Pacific. However, Atlantic walruses were heavily exploited by sealers in the eighteenth and nineteenth centuries—nearly leading to local extinction. Commercial walrus harvesting is now illegal throughout their range, which is somewhat circumpolar, extending from eastern Canada through parts of the Russian arctic to Alaska. However, moderated hunting is allowed to persist, with between 4,000 and 7,000 Pacific walruses harvested per year throughout the 1990s. It is unclear what effect, if any, this hunting is having on the species since it is listed as Knowledge Deficient by the IUCN.
Another, likely greater, threat to walruses is global warming. This year, sea ice in the arctic reached one of its lowest points since satellite monitoring began in 1979, and is expected to decline ever-further.
"A nearly ice-free summer is now forecasted to occur as early as 2016," write the authors of a study published earlier this year in PLOS ONE. "Such large-scale, precipitous environmental changes will be detrimental for many species dependent on sea ice habitats."
One of those sea ice-dependent species is the walrus.
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Walrus image via Shutterstock.