This was an invention of the Indians, who knows how long ago, that they shared with the white men when they arrived in Canada. Calling a bull moose while on the hunt. Any male in a raduis of about 5 miles will come running. When he arrives and discovers no female, he's going to be mad. If two males arrive this can happen.
Male moose are more than willing to fight over a female moose, a battle sometimes to the death.
People have found moose antlers in the woods that were locked together in combat with the moose starving to death afterwards. Moose at a body of water. Moose can swim very well, in fact the first moose I ever saw, probably back in 1977 or so was swimming across Rangley Lake in Maine. Sort of greenish or brownish things about the size of meatballs. I understand there's someone over in Maine who gathers the stuff, coats it with urethane or something and makes necklaces out of it.