What Do Moose Eat? Willow, Water Plants and Winter Browse

Browsers, not grazers

Many hoofed animals, such as cattle, bison and the North American elk, are grazers that feed largely on grass. The moose is a browser. It feeds mostly on woody plants, picking the most nutritious parts: fresh leaves and shoots in summer, and the tips of twigs in winter. Biologists call this kind of feeder a concentrate selector, an animal that chooses rich, easily digested food rather than eating large amounts of coarse fiber.

Moose eat a huge variety of plants. Studies in North America have recorded more than 200 plant species and genera in their diet, and in Russia more than 350, but a few favorites make up most of what they eat:

Willow, birch and aspen

Willows are the most important food in much of the moose’s range. In interior Alaska, willow has been found to make up more than 90 percent of what moose eat in winter. Birch, aspen, poplar, mountain ash and maple are other common foods. In Europe, young Scots pine can be a major winter food: in one study from Poland, trees and shrubs made up nearly 90 percent of the diet, and pine alone about half.

Moose are well equipped for this tough diet. They have no upper front teeth; instead, they press twigs against a hard pad on the upper jaw and nip them off with their lower incisors. Their large, flexible upper lip can grip a branch and strip the leaves off in one pull. To reach food high up, a moose may push a sapling over with its chest and walk along it, or rear up on its hind legs. Heavy feeding leaves a visible browse line, about 1.8–2.4 m (6–8 ft) above the ground, below which few twigs remain.

Water plants and the need for salt

In summer, moose spend much of their time in and around water. They wade into ponds, marshes and slow rivers to eat pondweeds, water lilies, horsetails and other aquatic plants, often plunging their heads beneath the surface and sometimes diving completely. The water also keeps them cool and gives some relief from biting insects.

Water plants matter because of sodium. Land plants in northern forests contain very little of this essential mineral, while water plants contain much more. Feeding in ponds in summer lets moose build up sodium they need for the rest of the year. The same craving draws moose to natural mineral licks and, in winter, to roadsides where salt is spread on icy roads, which increases the risk of collisions. You can read more about this habit in can moose swim?

How moose survive winter

Winter is the hardest season. Leaves and water plants are gone or frozen, and moose must live on twigs, buds and bark, which are high in fiber and low in energy. To cope, moose:

• Eat less and move less. They reduce their food intake and activity, saving energy instead of wandering in search of better food.
• Live off their fat. Fat built up in summer and fall carries them through the leanest months, and adults normally lose weight over winter.
• Use a four-chambered stomach. Like cattle and other deer, moose are ruminants. Microbes in the first chamber, the rumen, ferment tough plant material, and the moose later brings food back up to chew again, which is called chewing the cud.
• Choose good wintering areas. Many moose move to river valleys, willow flats or young forests where twigs are abundant and the snow is not too deep.

Deep snow, especially when it lasts into spring, makes feeding harder and leaves moose weaker and more vulnerable to predators such as wolves.

How much do moose eat?

An adult moose eats roughly 20 kg (45 lb) of plant food a day in summer, and large bulls more. Because winter browse is far less digestible, moose eat less by weight in the cold months and depend partly on stored fat.

Calves begin nibbling plants within a few weeks of birth while still drinking their mother’s milk, and they are weaned at about five months, in the fall. By then they have learned from their mother which plants to eat and where to find them.

How moose shape forests

With so much food passing through so many animals, moose have a big effect on their surroundings. Heavy browsing can stop young trees such as aspen, birch and fir from growing up, changing which trees dominate a forest. On Isle Royale in Lake Superior, decades of research show how moose numbers, wolf numbers and the growth of young balsam fir rise and fall together.

On Newfoundland, where moose were introduced in the late 1800s and early 1900s, browsing has held back the regrowth of native forests in some areas. In Scandinavia, foresters track moose damage to young pine plantations. Moose also spread nutrients through their droppings and create open patches that other animals use, so their influence is not only negative. For more on the plant-eaters of the deer family, see what do deer eat?