Here's another photo from the session at Wildpark Alte Fasanerie near Hanau, Germany.
These are two arctic wolf yearlings, well, playing.
The wolf to the right tries to entice the other wolf to play-chase her, and he is about to make it happen
The stalking-like appearance combined with a play-bow like posture is typical for play behavior. The tail is usually waving around too and held in T2 position (in extension to the spine, parallel to the ground) or a bit higher or lower.