Bulls Believe bigger is better
Alaska Science Forum
Dec. 23, 2009
Bulls Believe bigger is better
By Ned Rozell
The bull moose rocked his royal headgear from side to side, splintering
branches as he responded to a hunterıs grunt. The big bull was ready to
defend the females in his harem from what he perceived to be another bull.
Watching from a tree, the hunter was thankful for two things: one, he wasnıt
on the ground; two, he wasnıt a lesser moose on the ground.
In a mooseıs world, the big guys call the shots. Further proof of that came
from a study by former researchers at the University of Alaska Fairbanksı
Institute of Arctic Biology. Kelley Stewart and Terry Bowyer examined two
groups of moose, one each in Alaska and Russia. They came away on some
insights on how and why moose invest so much energy in antler development.
In just a few summer months, moose antlers grow from tiny knobs to immense
racks that weigh as much as 80 pounds. During June, the points on a mooseıs
antlers grow more than one centimeter a day. One pound of antler can be
added to a mooseıs head on a good day of growth.
Antlers are made of bone, which during growth is covered with furry brown
velvet. Velvet, rich with blood vessels, nourishes the antlers until they
stop growing and the bull scrapes the velvet off. A male moose needs plenty
of calcium and phosphorus during antler development. Most minerals come from
willow shoots; some moose chew bones and antlers to increase their intake of
The payoff for big antlers is worth gnawing a few bones. Dominant bull
moose, the ones with the biggest racks, are the animals that assemble and
defend harems of cows. They breed with the cows, passing on their genes,
while smaller bulls wait in the wings for a chance to sneak in and mate with
a dominant bullıs cows. Bowyer said thatıs not a good strategy.
³If they catch the little guy, theyıll kill him,² he said.
So whatıs a young moose to do? Stewart and Bowyer discovered that moose
younger than about eight years old probably donıt mate often. Their
developing bodies need the minerals that a full-grown bull (about eight to
11-years-old) can invest directly in its antlers. Stewart said young moose
would save energy if they didnıt develop antlers, but perhaps they need them
to spar with younger bulls and develop their pecking order. When a moose
reaches full size and its body growth is complete, it can shunt most of its
calcium and phosphorus into its antlers, perhaps even borrowing some from
In the best-case scenario, a dominant bull avoids fights by intimidating
other bulls by the sight of its rack alone. But another male of similar body
and antler size forces even the biggest bull to fight. Bulls clash their
antlers, knocking them together and pushing like sumo wrestlers until one
backs down. The battles are extremely energy consumptive and sometimes fatal
for the loser. The victor is often the one that invested ample energy into
growing antlers but saved enough to develop a strong body.
This column is provided as a public service by the Geophysical Institute,
University of Alaska Fairbanks, in cooperation with the UAF research
community. Ned Rozell is a science writer at the institute. This column
first appeared in 1999.
Interesting article but I doubt the age classification is correct. I would agree 8-11 w/ sheep but think moose is more like 5-9.
i agree with 5-9 years of age
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