The Arctic Wolf appears in the campaign scenario A Lost People, as well as in Rampage (where three of them guard a Relic). It is similar to the regular Wolf, but slower, gives slightly more food (125), and attacks any unit that comes too close, not just Workers. Also, their pelts are white, rather than grey-brown.
They can also be found on the Tundra map, using a second version of the unit.
"Scientific name -- Canis lupus arctos
Size -- 80 - 175 lbs.
Diet -- Caribou, musk oxen, arctic hare, small mammals
Arctic wolves inhabit some of the most inhospitable terrains on the earth. Their extra long fur and white coloring allow them to live in sub-zero temperatures and remain hidden against snowy backgrounds to stalk their prey.
Arctic wolves hunt together in large packs and will take down any animal they can catch. Musk oxen and caribou are too large for any one arctic wolf to handle alone. Because of the openness of the terrain in which they hunt, they rarely have the element of surprise and generally force herds into defensive circles, which they will stalk until they can isolate the weak or young. One musk ox can feed a group of wolves for several days.
Wolves in general have been endangered throughout history. The arctic wolf is one of the few that still largely roams over its entire terrain, mostly because it rarely encounters humans in its inhospitable habitat."—In-game help section