I have mentioned about how moose re-grow their antlers each summer. Moose will drop or loose their antlers during the winter. Sometimes a sharp eye will spot the cast-off antlers on the shore or inland from the lake. These make interesting souvenirs.
These ones where likely dropped last winter and as is often the case, both sides fell off near the same time. Sometime a moose will wander for a while with just one antler.
You will notice in the picture that the antlers look a little chewed up. Many small creatures from porcupines to mice will chew these cast-offs for a great source of calcium. Nature has it own methods of recycling. Nothing goes to waste.