Moose, the largest members of the deer family, possess impressive bony structures on their heads. These are antlers, not horns, and unlike permanent horns, moose shed their antlers annually. Antlers are composed of bone and grow directly from the skull, unlike horns which have a bony core covered in keratin, the same material found in human fingernails. Male moose, known as bulls, are recognized by their broad, often shovel-shaped antlers, which can span up to six feet across.
The Annual Cycle of Antler Growth and Shedding
Antler shedding occurs in late winter or early spring, generally between December and March. This process is triggered by hormonal changes, specifically a decrease in testosterone levels after the mating season. A specialized layer of cells, called the abscission layer, forms at the pedicle, the point where the antler attaches to the skull, weakening the connection and allowing the antler to detach. This shedding is painless for the moose.
Following shedding, rapid regrowth begins in the spring. New antlers emerge from the healed pedicles, initially covered in a soft, vascular skin known as velvet. This velvet contains a dense network of blood vessels that supply oxygen and nutrients for bone growth. Antlers are among the fastest-growing tissues in the animal kingdom, with mature bull moose capable of growing up to an inch per day.
As summer progresses into late summer or early fall, antlers reach their full size and begin to harden. The blood supply to the velvet diminishes, causing it to dry out. Moose remove the dried velvet by rubbing their antlers against trees and shrubs. This rubbing polishes the bone, revealing the hard, solid antler ready for the mating season. The entire cycle of growth, hardening, and shedding is regulated by the bull’s changing testosterone levels.
The Purpose of Antlers
Antlers serve functions for male moose during the autumn mating season. They function as visual displays to attract females, with larger antlers signaling a bull’s health and strength. Antlers are also used to establish dominance among rival males. If intimidation is insufficient, bulls use their antlers for sparring or fighting, locking them together in contests of strength to secure mating rights.
Female moose generally do not grow antlers, with rare exceptions usually linked to a hormonal imbalance. The energy investment required to grow and maintain such large bone structures is substantial, and for females, this energy is instead directed towards reproduction and calf rearing.
Once shed, moose antlers contribute to the ecosystem. They are a valuable source of calcium, phosphorus, and other minerals that are important for the diets of various other animals. Rodents like mice, squirrels, and porcupines, along with other animals such as deer, bears, and coyotes, frequently gnaw on shed antlers to obtain these essential nutrients, especially in areas where soil minerals may be deficient. This consumption, along with natural decomposition, returns the minerals to the soil, contributing to nutrient cycling within the forest ecosystem. This ecological role is a primary reason why finding intact shed antlers in the wild can be challenging.