Walrus

Walruses (Odobenus rosmarus) are large mammals that live in arctic regions. In the wake of global warming and after the extinction of their natural predator, the polar bear, walruses have quickly mutated and evolved to gigantic proportions, sometimes exceeding five tons. 
Walruses inhabit the island Kvitøya and have a habit of slipping into Valhalla, where they must be rounded up and expelled. Walrus detail is given to most teams at various times, but when a team finds itself with three members, they are condemned to near constant walrus duties.
Walrus Detail or Walrus Duty generally consists of following Alopex to where a walrus was spotted, then directing the beast with sonic emitter sticks toward the walrus cages, which are then taken by crane to the surface.
Known walruses include Umberto and Orson.
== Behind the Scenes ==
In the original screenplay on which the Valhalla trilogy is based, the base was plagued by giant penguins. Research showed though that penguins are at the South Pole, not the North, so Walruses were substituted.
Bach posted an additional reason for the walrus size explosion on "Facts I Just Made Up":
The Great Marshmallow Disaster of 1992
Derbyfield Marshmallow Plant was located in the Maydupp Mountains 
directly outside of Toronto Canada. Founded in 1807, it was the longest 
running marshmallow manufacturing plant in the Americas, and the second 
longest on Earth after only Mashumaro in Japan, where the candy was 
invented in 1322.
In 1992, the factory switched owners. Rolf Jensen, the previous owner
 and manager was well loved by all his employees and brought in the 
highest profits and maintained the best safety record of any owner the 
factory ever had. His replacement, Donald Bush from the U.S. was 
considered a total mess. He bought the factory with his father’s riches 
shortly before he left the U.S. Presidency. Bush inherited the factory 
at its best, and within only two months had the worst safety record, 
limited production, and was almost 2 million dollars in the red.
A strike ensued, and many employees simply quit. Bush, undaunted, 
decided he could do the jobs himself. He worked hard, nobody could deny 
it, but his incompetence was off the scale and when a vat of sugar was 
allowed to come into contact with the fluffing epoxy, the factory 
exploded in the mass seen above, killing Bush and several picketing 
employees, smothering them in delicious deadly goo.
The region has been declared a disaster zone and a biohazard, and is,
 like Chernobyl, impossible to clean up using modern technology. Not all
 the effects of the disaster are negative however, as the local Walrus 
population has skyrocketed and grown to epic proportions on the fluff.