By Misi Stine, Environmental Educator and member of the MN Herpetological Society

Minnesota moose (Alces alces) are the most prominent members of the deer family (cervids) in the state. Northern Minnesota represents the southernmost extent of their range in North America. The habitats where you're most likely to find moose are mixed boreal forests and wetlands, which provide their essential needs: food, shelter, and protection from predators.

Moose are cold-adapted animals that are very sensitive to heat. Due to this, dense shade and cool water during the summer are crucial for their overall health. Moose primarily eat leaves, twigs, and bark from trees and shrubs. The prefered habitat is young forests that have been recently disturbed by logging or wildfires. Their preferred food sources include aspen, birch, and willow. In older forests, they browse conifers such as fir and spruce.

Moose are also well known for their swimming abilities. They often spend time in lakes, ponds, or slow-moving streams to escape heat and reduce the impact of biting insects. These water bodies also contain sodium-rich aquatic plants, such as lilies and pondweed, which provide essential minerals for their diet, including sodium.

This iconic species holds cultural, ecological, and economic significance, and is a symbol of the Northwoods. Unfortunately, Minnesota's moose population has experienced steep declines, and the reasons are complex. There are two distinct moose populations in the state. The northwestern population, which once numbered around 4,000 in the mid-1980s, has now dwindled to fewer than 100 animals—nearly extirpated. The northeastern population has also declined sharply but has shown signs of stabilization in recent years. This population peaked in 2006 at an estimated 8,840 moose. Between 2009 and 2013, the population dropped to between 2,760 and 3,386. Since then, the population has stabilized. In 2025, the moose survey estimated around 4,040 individuals, a slight increase from the previous year’s estimate of 3,470.

Causes of Decline

As noted, the causes of moose decline are complex, involving multiple environmental and biological stressors. Below are three primary contributors:

1. Parasites

Brainworm (Parelaphostrongylus tenuis) is considered a leading cause of decline, particularly in northwestern Minnesota. This parasite affects the nervous system, leading to severe neurological disease, progressive paralysis, and eventually death. White-tailed deer (Odocoileus virginianus) are the natural hosts for brainworm and are unaffected by the infection. Moose, however, become infected when they accidentally ingest snails or slugs—intermediate hosts for the parasite’s larvae.

What some may not realize is that in pre-colonial times, moose and deer did not share the same habitats. Human activities, such as logging, have altered the landscape, increasing overlap between species and, consequently, brainworm transmission.

One proposed mitigation strategy is to lower deer populations in the moose range and restore moose habitat. However, this is a controversial issue, as many people in the Northwoods enjoy deer hunting and are reluctant to support reduced deer numbers.

Winter ticks (Dermacentor albipictus) are another parasite that negatively impacts moose. Moose have always lived with ticks, but warmer and shorter winters—caused by climate change—now provide favorable conditions for tick populations to thrive. An indivdual moose can have tens of thousands of ticks on their body. These ticks feed on the animal's blood, causing significant blood loss, anemia, and weakened immune function. Moose often groom obsessively to remove the ticks, leading to hair loss that increases the risk of hypothermia during winter. The resulting poor body condition reduces fat stores, compromises immunity, and makes them more vulnerable to disease and predation.

Tick infestations are especially lethal for calves. Studies have shown that up to 50% of calf deaths each year are linked to severe tick burdens. Addressing winter ticks is particularly difficult because it would require global action to combat climate change—something that remains politically and logistically challenging.

Other parasites also affect moose. Liver flukes (Fascioloides magna) can cause mild to severe liver damage and infection, which may lead to death. Hydatid cysts, found in the liver or lungs, are caused by the Echinococcus granulosus tapeworm. These cysts can be fatal in severe cases and may increase predation risk due to impaired organ function.

2. Climate Change

Because moose are adapted to cold climates, the warming temperatures in northern Minnesota have a significant impact on their survival. Their thick, insulated fur and large body size are excellent for retaining heat, but they also make them vulnerable to heat stress. Moose can begin to overheat when temperatures exceed 57°F in summer or 23°F in winter.

To cope, they change their behavior: they pant, seek shade or cool water, and reduce their movements. While this helps regulate their temperature, it also reduces their foraging time. Less foraging means fewer calories, which negatively impacts body condition, reproductive success, and resistance to disease and predation.

Climate change is also expected to alter forest composition, reducing both thermal cover and the availability of cold-tolerant plant species, which are a key part of the moose's diet. Additionally, warmer temperatures support the expansion of white-tailed deer populations, which increases overlap with moose and promotes brainworm transmission. Warmer conditions also allow parasites like ticks to survive longer and in greater numbers.

3. Predation

Photo credit: Carl Brandt (Swedish, 1871 - 1930), Public domain, via Wikimedia Commons

Moose weakened by parasites, heat stress, and malnutrition are more vulnerable to predation. The primary predators in the Northwoods are the gray wolf (Canis lupus) and the black bear (Ursus americanus). Research shows that many moose killed by wolves had underlying health problems. In one study, 40–44% of wolf-killed moose suffered from conditions such as encephalitis, meningitis, pneumonia, brainworm, or severe tick infestations.

Interestingly, wolves may offer an indirect benefit to adult moose by preying on white-tailed deer. This can reduce the risk of brainworm transmission. Wolves also influence the movements and habitat use of deer and moose, creating a complex set of interactions that highlights the dynamic nature of predator-prey relationships.

What Can We Do?

There are practical steps we can take to support Minnesota’s moose:

- Restore moose habitat by planting trees that are part of their natural diet.

- Consider reducing deer populations in moose range while balancing the needs of deer hunters through acceptable alternatives.

- Protect critical wetlands and aquatic habitats that moose rely on for survival.

- Talk with others about the impact of climate change and how it is related to habitat loss and moose decline.

I've participated in numerous discussions about whether moose will continue to inhabit Minnesota in the coming decades. It's difficult to predict—but I certainly hope so.

Bibliography and additional resources (generated with the assistance of Google Gemini)

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