Wolves are the only hostile animal in the Shelter 2 base game (Bears, Foxes and Eagles came with the Mountains DLC). Wolves exclusively appear in the tundra marked by the snowflake on the map. They are all light grey except for their leader, which is white.
Tutorial
The wolves first appear in the game tutorial. They first appear in split-second cutscene. After taking a few steps they come out of the mist to pursue you. As you run through the canyon you also pass by wolves howling above you. You frequently hear their barks and growls as you run. If you slow down, they catch you and the tutorial restarts. You eventually jump onto a cliff and see them barking and growling in vain, unable to pursue you.
Arrival and How to Escape
Wolves, like other disasters, are marked by the sky darkening. Further indicators are the music changes to a tribal-style drum track and wolf howls. You have a few moments to locate a hilltop (a round, upraised hill or ledge that is flat on the top and gives you a jumping prompt when you approach. Not to be confused with the mountains surrounding the tundra) before they arrive. Your kits should immediately follow you when you jump onto a hilltop (unless you are on the hard difficulty). If on survival mode, you must carry them all up, so best to avoid tundra overall. The wolves actually appear when you hear barking and growling, and see a pack of wolves. They should surround the hill (or, if you are on the ground kill you or a kit) and continue to bark. They also jump at the hill but cannot get up. Eventually they lose interest and leave, with the sky and music turning back to normal.
If you leave a carcass of any species on the ground, uneaten, then the wolves will eat it and leave.