Moose are herbivores. Moose begin antler growth in late winter. The antlers start as soft tissue, called velvet. The velvet dries up as the antlers harden into bone by late August, and peels away by early September to reveal the rack of antlers. Moose antlers serve their purpose during the moose mating season from about September 15th to October 15th, also called the moose rut.
Bulls defend their right to mate with a cow and sometimes a group of cows with their antlers.
They also use them to attract a mate. Bull moose become most aggressive during the rut. A moose watcher is wise to keep a distance from any bull moose during the rut. In early winter, after the mating season, moose shed their antlers to help reduce their energy needs. Moose calves are lighter colored and have shorter noses than their parents.