Maine is home to the largest moose population in the contiguous United States, with recent state wildlife agency estimates placing the number between roughly 60,000 and 70,000 animals. That figure represents a decline from a peak of about 76,000 in the early 2010s, and the downward pressure is not easing. The forces behind that slide, particularly a tiny parasite thriving in warmer winters, make the trajectory of Maine’s moose herd one of the more closely watched wildlife stories in the Northeast.
Where the Estimate Comes From
The Maine Department of Inland Fisheries and Wildlife (MDIFW) monitors moose through a combination of aerial surveys, harvest data, and population modeling. The state is divided into Wildlife Management Districts, with moose concentrated heavily in the northern and western regions. Southern Maine has far fewer moose, largely because the habitat is less suitable and white-tailed deer densities are higher, which introduces disease risks covered below. Because moose are solitary and spread across vast, densely forested territory, population counts always carry uncertainty. The numbers MDIFW publishes are modeled estimates rather than direct headcounts, and they can shift as survey methods are refined or new data comes in.
Northern New Hampshire and western Maine together form the core of what researchers describe as the largest regional moose population in the continental United States.1Canadian Journal of Zoology. Mortality assessment of moose (Alces alces) calves during successive years of winter tick (Dermacentor albipictus) epizootics in New Hampshire and Maine (USA) That distinction matters because it means what happens to moose in Maine reverberates across the broader regional population. A decline here is not easily offset by gains elsewhere.
Why the Population Has Been Falling
The single biggest factor driving moose declines in Maine and across the Northeast is the winter tick. Unlike the common deer tick most people think of, winter ticks are a different species that specializes in large-bodied hosts. Tens of thousands of these ticks can latch onto a single moose in autumn, feed through the winter, and engorge in spring. The blood loss is staggering. Heavily infested moose become anemic, lose body condition, and frequently die in late winter or early spring. Calves are especially vulnerable because their smaller bodies cannot tolerate the same blood drain an adult can.
Research tracking collared moose calves in New Hampshire and western Maine found that the majority of mortalities were associated with moderate to severe winter tick infestations, with over half of calves dying by late winter in epizootic years.1Canadian Journal of Zoology. Mortality assessment of moose (Alces alces) calves during successive years of winter tick (Dermacentor albipictus) epizootics in New Hampshire and Maine (USA) A companion study in Vermont documented winter calf survival as low as 37% in a bad year, with winter ticks responsible for the vast majority of calf deaths.2The Journal of Wildlife Management. Effects of Winter Ticks and Internal Parasites on Moose Survival in Vermont, USA Adults fare better, but not perfectly. Adult survival in those Vermont study years ranged from 84% to 90%, and winter ticks still accounted for about a quarter of adult deaths.2The Journal of Wildlife Management. Effects of Winter Ticks and Internal Parasites on Moose Survival in Vermont, USA
The damage extends beyond outright mortality. Alongside the calf die-offs, researchers have documented declining productivity in adult females. Twinning rates and calving rates have both dropped in the northeastern United States as tick burdens have worsened.3Frontiers in Ecology and Evolution. Metabolic and Population Effects of Winter Tick Infestations on Moose: Unique Evolutionary Circumstances? Fewer calves being born, combined with more calves dying before their first birthday, is a formula for population decline even if adult survival holds relatively steady.
The Climate Connection
Winter ticks have always been part of the moose-parasite landscape, but the frequency and severity of tick epizootics have increased in recent decades. The reason is straightforward: shorter winters and milder conditions favor the tick’s life cycle. Winter ticks drop off their host in spring to lay eggs on the ground. An early, warm spring lets more ticks survive to lay eggs, and a late, warm autumn gives newly hatched ticks a longer window to find a host before snow cover arrives. Research linking weather data to tick abundance found that warmer springs and increased precipitation are associated with higher tick loads on moose, suggesting climate change could continue amplifying this problem.4The Journal of Wildlife Management. Linking weather conditions and winter tick abundance in moose
Heat stress also affects moose directly, separate from the tick issue. Moose are built for cold. Their massive bodies, dark fur, and thick insulation make them poorly equipped for warm weather. Studies tracking moose behavior at the southern edge of their range found that moose reduce travel and increase resting when ambient temperatures climb above roughly 14°C in spring and about 24°C in summer.5PubMed Central. Moose at their bioclimatic edge alter their behavior based on weather, landscape, and predators That behavioral shift means less time foraging, which compounds the nutritional stress from ticks and parasites. Maine sits at the southern fringe of global moose range, so its animals already live in warmer conditions than moose in Canada or Alaska. As average temperatures creep upward, the livable zone for moose contracts northward, and Maine’s population sits squarely in the squeeze zone.
Meningeal Worm and Other Parasites
Winter ticks get most of the attention, but they are not the only parasite stressing Maine’s moose. The brain worm, formally called meningeal worm, is a parasite naturally carried by white-tailed deer, which tolerate it without serious harm. Moose, however, are dead-end hosts. When a moose accidentally ingests the larval stage of the parasite through contaminated snails or slugs on vegetation, the worm migrates through the nervous system and can cause neurological damage or death.
This parasite has historically kept moose from thriving in areas with high deer densities. Where deer are abundant, meningeal worm transmission to moose increases, effectively creating a zone of exclusion.6Ecological Applications. Parasite‐Mediated Competition in Deer and Moose: How Strong is the Effect of Meningeal Worm on Moose? This is one reason moose numbers are much higher in Maine’s northern forests, where deer are sparse, and lower in southern Maine, where deer thrive. As deer expand their range northward in response to milder winters, the overlap zone with moose grows, and so does the risk of brain worm transmission.
In the Vermont survival study, about a third of all moose mortalities showed evidence of meningeal worm infection, and statistical modeling suggested that the combination of winter ticks and internal parasites like roundworm and lungworm together had a compounding negative effect on calf survival.2The Journal of Wildlife Management. Effects of Winter Ticks and Internal Parasites on Moose Survival in Vermont, USA In other words, a calf dealing with heavy tick loads and a worm infection simultaneously is in far worse shape than one facing either threat alone.
Hunting as a Management Tool
Maine runs a moose hunting season that is tightly controlled through a lottery permit system. Hunters must apply each year for a chance to hunt in one of the state’s Wildlife Management Districts, which collectively cover over 21,000 square miles across six zones.7ScienceDirect. An empirical study of option prices for hunting permits Successful applicants receive a permit for a hunting season lasting about six days. The number of permits issued each year is one of the primary levers MDIFW uses to manage the population.
In recent years, the state has experimented with increasing the number of permits in some districts specifically to reduce moose density and, in turn, reduce winter tick loads. The logic is counterintuitive: kill more moose now so that fewer moose die miserably from ticks later. When moose density drops, each individual tick larva sitting on the ground in autumn has a lower chance of finding a host. With fewer hosts carrying fewer ticks through the winter, the total tick population crashes, and surviving moose enter spring in much better condition. This approach is sometimes called “adaptive management” or a “density reduction” strategy, and it has been a subject of active research and public debate in Maine. Hunting permits have risen in some northern districts as part of this effort, while southern districts where moose are already thin on the ground receive few or no permits.
The lottery itself is enormously popular. Demand for permits vastly exceeds supply, and a Maine moose tag is one of the more coveted hunting permits in the eastern United States. That cultural significance gives MDIFW a built-in constituency that supports moose management, though the specifics of how many permits to issue and where always generate heated discussion.
Moose on the Road
For many Mainers, the most immediate moose-related concern is not population biology but highway safety. Moose-vehicle collisions are a serious hazard, particularly in the western and northern parts of the state. An analysis of over 8,000 collisions in western Maine between 1992 and 2005 found that most occurred from May through October, with June being the peak month. Collisions clustered along certain road segments, and both higher traffic volume and higher speed limits were strong predictors: for every additional 500 vehicles per day on a road, the odds of a collision went up by 57%, and for each increase in speed limit, the odds climbed further.8The Journal of Wildlife Management. Temporal, Spatial, and Landscape Habitat Characteristics of Moose—Vehicle Collisions in Western Maine
Landscape also matters. Collision sites tended to be surrounded by more cutover forest and coniferous cover, and less deciduous-mixed forest, than random points along the same roads.8The Journal of Wildlife Management. Temporal, Spatial, and Landscape Habitat Characteristics of Moose—Vehicle Collisions in Western Maine Recently logged areas produce the kind of young, regenerating vegetation moose love to eat, so roads cutting through or near these areas become hotspots. This means forest management practices indirectly affect collision risk. Researchers have suggested that reducing collisions will require a combination of speed reductions and modifications to how forests are managed along roadways, because neither approach alone addresses both the human and the landscape side of the equation.
Genetic Diversity Concerns
Beyond the immediate threats of parasites and climate, there is a longer-term worry about genetic health. A large-scale genetic study using samples from 507 moose across five northeastern U.S. states and one Canadian province found low genetic diversity overall, with a high proportion of genomes sharing identity by state and no consistent evidence of non-random mating.9Conservation Genetics. Genetic diversity and connectivity of moose (Alces americanus americanus) in eastern North America In plain terms, the moose of the Northeast are genetically similar to one another, more so than you might expect for a population spread across such a wide area.
That lack of diversity reflects the species’ turbulent population history in the region. Moose were nearly eliminated from much of New England by the early 1900s due to unregulated hunting and habitat loss, then rebounded dramatically through the twentieth century as forests regrew and protections were put in place. That rebound likely involved relatively few founding animals expanding into vacant territory, which narrows the gene pool. Low genetic diversity makes a population less resilient to new diseases, parasites, or environmental shifts, because there is less raw material for natural selection to work with. Physical barriers like highways and developed areas can further fragment moose populations and limit gene flow between subgroups. For a species already under pressure from warming temperatures and parasites, limited genetic flexibility is an added vulnerability that wildlife managers are just beginning to quantify.
How Moose Shape the Forest
The conversation about moose numbers often focuses on what threatens moose, but moose also profoundly shape the ecosystems they inhabit. A moose is not a passive occupant of the forest. It is a selective browser that eats enormous quantities of woody vegetation, and its feeding preferences alter what grows and what does not.
Long-term research comparing fenced plots that excluded moose with unfenced plots that moose could freely browse showed stark differences in forest structure. In areas where moose browsed, tree biomass was significantly lower, while shrub and herb layers were denser, because moose prevented preferred tree saplings from reaching the canopy.10Ecology. Effects of Moose Browsing on Vegetation and Litter of the Boreal Forest, Isle Royale, Michigan, USA The result is a more open understory with a different mix of plant species than would exist without moose. Where moose reach very high densities, browsing can go further, converting regenerating forest stands into open areas dominated by grasses and shrubs and reducing the understory cover that songbirds and other wildlife depend on.11Diversity and Distributions. Multiscale impacts of forest degradation through browsing by hyperabundant moose (Alces alces) on songbird assemblages
This ecological role means that moose population size has cascading consequences for the forest itself. Too many moose can suppress forest regeneration, reduce habitat for other species, and even alter nutrient cycling in the soil. Too few moose allows dense canopy closure that shades out the understory vegetation other animals need. For Maine’s timber industry, which relies heavily on regenerating forest, moose browsing is a practical concern as well as an ecological one. The state’s management decisions about moose numbers ripple through the entire forest ecosystem, affecting everything from bird populations to the commercial value of timberland.
Where Things Stand and Where They Are Headed
Maine’s moose population remains large by lower-48 standards, but the trajectory has shifted from growth to managed decline over the past decade. The combination of worsening winter tick epizootics, expanding white-tailed deer range bringing brain worm farther north, and the underlying engine of warming winters creates a set of pressures that are all moving in the same direction. MDIFW’s strategy of using increased hunting permits to reduce moose density in the hardest-hit districts is an attempt to break the tick cycle, and early results from similar programs in neighboring states have shown some promise in reducing tick loads where moose densities drop. Whether that approach can keep pace with the rate of climate warming is an open question that researchers are actively studying.
For anyone planning a trip to northern Maine hoping to spot a moose, the animals are still abundant. Drive Route 15 through the Moosehead Lake region or the logging roads of the North Maine Woods in early summer, and you will almost certainly see them standing in bogs, wading through ponds, or looming along roadsides at dusk. The population may be smaller than it was a decade ago, but 60,000-plus moose spread across Maine’s vast northern forest still makes for one of the densest moose populations anywhere in North America south of the Canadian border. The concern is less about whether you can find a moose today and more about what the herd will look like in another twenty years if the parasites and the thermometer keep trending the way they have been.