May Moose Antlers

These spring moose antlers on this older bull will grow to nearly 5' wide and 50 lbs by fall

Two mornings ago, I headed up into the Many Glacier valley after working all night just a few miles away. It was nice and quiet on the human front at 4 a.m. - too dark for the roving herds of ubiquitous photographers, too early for the glassy-eyed employees who live there. But the animals were active as always, and I counted seven moose feeding between the highway and developed area, five adults and two yearlings, including a pair who appeared to be looking in the windows of one residence.

Moose calves won't hit the ground until early June. But the male equivalent, antlers, started appearing several weeks ago. Energetically speaking, a pair of calves and a large pair of antlers are supposed to require about the same amount of caloric input. Cows give birth to 1 or 2 calves weighing 25-35 lbs. each, while big bulls grow a pair of annual antlers that span up to 60" wide with a combined weight of up to 50 lbs.

Moose are the largest member of the deer family, and in Montana we have the smallest sub-species, the Shiras' moose (Alces alces shirasi). Regulating hunters helped North American moose populations grow for most of the 20th century, but populations started plummeting again in the early 1990's. A combination of factors include at least two that are related to climate change. Moose evolved in cooler climates, and they do not have sweat glands for cooling in summer. Increasingly, heat stress is causing moose to seek shade and remain inactive for long periods. And warmer winters means less tick kill-off, and tick infestations are now growing and weakening otherwise healthy moose, which are then more susceptible to predation and disease.

Yearling moose in pre-dawn light

Instead of facing the new reality, Montana punted by initiating an 8-10 year study to identify the (known) causes of declines. The state agency seemed to feel this was necessary because they feared the bellicose minority of "hunters" who think that all wild animals belong exclusively to good ol' boys with more bullets than brain cells. They blame the moose decline on wolf reintroduction, of course, as if moose and wolves didn't evolve together over many thousands of years, both surviving quite well until the 1990's. Waiting 10 years allows the current managers to avoid the consequences. Unfortunately, moose don't have that option.

Moose Teenagers

Yearling bull moose plucking young aspen leaves

Yearling moose (Alces alces) head off on their own around this time of year - but not always by choice. As young calves they followed mom around through the deep winter snow. But as spring turns to summer, mom starts getting a little impatient with their lingering presence. She is driven to breed again, and she can't have a teenager hanging around her forever.

Fortunately, the leaves are at their nutritional peak in early summer, so the young moose that made it through winter will get a healthy boost just as they are moving towards independence, and as the males start growing their first set of antlers. A mouth full of tender aspen leaves hits the spot for young and old moose alike.

Aquatic Alces

Cow moose swimming across our lake

Awoke this morning to a bug-eyed moose swimming through the front yard. It's not every day I get to write that sentence. But it seems like once a year, here at the end of the road, we spot a moose swimming across our mile-wide lake. It always makes us nervous, what with their spindly legs and all, but moose (Alces alces) are actually pretty good swimmers.

I dug up an unconfirmed mention of moose swimming nine miles at a time, which would be rather amazing and somewhat suspicious. Moose eyesight is reported to be somewhat poor relative to other wild animals, so what incentive would a moose have to swim so much further than it can clearly see? Following a scent? Fleeing biting insects? Regardless of the reason, a one-mile swim is almost a mile further that I can paddle these days, so I should feel less suspicious and more amazed.

Why Did the Moose...

...cross the creek?  He might have been wondering the same thing after loosing his footing halfway across. McDonald Creek up in Glacier Park is below flood stage but still running high. It's been about three weeks since we were last able to cross the creek in neoprene chest waders. But then, my legs are half as long as those on today's young, lanky bull. Those moose legs come in handy when he's reaching for tender, end-of-branch leaves and buds in the brushy thickets. But later this summer, he will have to twist and turn his head just to fit his growing antlers between branches. Everything comes with a price.

Moose Seasons

Moose cow and 30 lb calf in June

Each summer in Montana, the wobbly moose (Alces alces) calves of June hit the ground at 30 lbs, walking on day one. By fall, these calves will weigh 300 lbs. They’ll browse beside mom through winter and spring before becoming independent during their second summer. Moose calves that survive their first year will outgrow the abilities of most predators, other than humans.

A male moose calf will eventually grow into a 1,200-pound bull, producing annual antlers that weigh up to 75 pounds. A female calf will grow into a 700-pound cow moose and begin breeding at age two. By age four, she’ll often produce twin calves each summer.

While non-human predation has little effect on moose populations, it’s a different story when Old Man Winter arrives. By January, bulls are shedding their antlers and cows are three months pregnant. And the eight-month-old moose calves are going through the most vulnerable period they’ll ever face.


Moose cow and 300 lb calf in October

During a moose’s first winter, there’s a significant correlation between calf survival and snow accumulation. Deeper snow means more difficulty reaching food, and a higher predation risk. A healthy calf will save calories and avoid starvation by following the path that his long-legged mom plows through his first winter. But a weaker calf floundering through deep snow is a likely target for large animals that hunt cooperatively during winter - like wolves.

That’s pretty straight-forward. What’s less obvious is the cumulative effect that snow depths from many previous winters can have on moose survival and twinning rates.

Research from a closed, island ecosystem (Michigan’s Isle Royal) showed a significant relationship between moose winter survival/twinning rates and the sum of snow depth for as many as seven previous winters. And as much as one-half of the variability in the moose population size was directly correlated to the sum of snow accumulations during the previous three winters.

How can winter snow depth affect a moose calf born three years later? Nutrition.

The difficulties of feeding in deep snow affect the pregnant cow’s nutrition, and this negative influence on her health can apparently accumulate for many years. Meanwhile, the cumulative effect on the female shows up each year in her calves. A relatively weaker moose mother produces fewer twins, and the calves that she does produce are more vulnerable during that critical first winter.

It should be pointed out that the same study found no strong correlation between moose survival and the numbers of wolves. Wolf predation on moose calves was secondary to the effects of winter weather on the cows, when the moose population was followed over many years.

Moose nutrition relates to the quality and quantity of the plants they eat. During spring, summer and fall, an adult moose might eat 50-60 pounds of plants each day. During winter, when plants are harder to come by, moose survive on the woody stems of several less-nutritious shrubs.

In the Gallatin Mountains of southern Montana, the most important winter moose foods are the leafless stems of western serviceberry (Amelanchier alnifolia), chokecherry (Prunus virginiana), and red dogwood (Cornus stolonifera). These woody shrubs remain important into spring, when moose add relatively more nutritious currants (Ribes spp.) and forbs to their diets. During fall, the most important moose foods are low red huckleberry (Vaccinium scoparium), subalpine fir (Abies lasiocarpa), and willow (Salix spp.).

In other parts of our state, moose rely more heavily on willow, grasses and aquatic plants – whatever it takes to survive Old Man Winter through to another Montana summer, and another round of wobbly moose calves.


1,200 pound bull moose in fall