Wapiti

Wapiti bull (right) and red deer stag (left).
The most distinctive difference is that the wapiti bull (on the right) has a large cream rump patch (around the tail). The fur of the wapiti is slightly more fawn-coloured and the antlers are a bit more palmate (hand-like) than those of the red deer stag.
Photograph: Fiordland Wapiti Foundation