The Role of Landscape Ecology in Moose Collisions

Maine is largely known for its keystone species the Moose, who are celebrated through many different kinds of tourist memorabilia such as signs and jackets. Individuals travel to Maine to catch a glimpse of this silent giant or to take up guns to hunt one of North America’s largest land mammals. Every year the Maine Department of Fish and Wildlife gives permits to hunters to keep down Moose populations. In 2021, 3,800 such permits were given to hunters (Warner 2021). However, encounters between humans and moose are usually a surprise rather than planned. This can create the most injury and economic loss when these occurrences happen on the road (Maine Interagency, 2001). This article will take a look how and why these accidents between large ungulates and humans occur and what the future of the Moose looks like in Maine.

Maine is considered a rural state, with most of the population density established along the coast. Portland, one of the main cities, has around 66,000 residents (US Census, 2019). There are few state highways and travel occurs mostly on secondary and arterial roads. The state has always been very resource driven, and has many logging companies and hospitals. Historically the roads have been altered from dirt carriage roads that connected remote towns to each other. Most of their design was for human convenience, and because of the slower movement of vehicles, collisions were uncommon and habitat fragmentation was never an issue. As vehicles became more advanced the roads became paved and stayed on the same winding paths through the trees and along wetlands. This lack of design foresight creates a problem for today, where the roads are only wide enough for two cars. On most secondary roads there is no shoulder, only a gravel embankment abuting the road with only an 8 ft vegetation clearance. (Maine Interagency, 2001)

The Moose is the largest of the deer family and has an affinity for water. They can close their nostrils and hold their breath for up to 60 seconds while eating underwater plants, and are also avid swimmers (Geist, 2021). During the summer months they will eat leaves, twigs, and occasionally bark from the willow, aspen, birch, maple, pin cherry and mountain ash trees along with salty water plants such as pondweed and water lily (Geist, 2021) (Innes, 2010). Because the plants they eat lack nutrients they are avid mineral searchers, often visiting natural springs. During the winter months they will often be attracted to roadsides, where de-icing salt will drain (“Species Spotlight”, 2021). When their usual tree leaves and twigs have died for the winter, Moose will generally turn to fir and yew trees and will eat the needles (Innes, 2010). Their coats grow so thick in the winter that they have been known to withstand up to -40°F. Because of their very specific temperature requirements and coats, Moose will overheat at certain temperatures. During the summer they cannot withstand temperatures higher than 57°F and during winter that tolerance drops to 23°F (Montgomery et. al, 2019). Because of these temperature tolerances Moose will travel south from New Brunswick, Canada to Maine, USA during the winter months, and north for the summer.

Moose are constantly traveling and are most active in the dawn and dusk hours. Their affinity for road salt, timing of their activity, and narrow fast roads combine to make disaster happen just about anywhere. In 2018 there were roughly 256 vehicle collisions with Moose in the State of Maine. This was a dramatic drop from the amount of collisions from the 2011-2015 Maine Department of Transportation statistics which averaged around 364 collisions per year (Holyoke, 2021)(Maine DOT). While few such incidents are fatal to people, the amount of damage they incur has horrific potential. Their bodies can weigh up to 1400 lbs, and the length of their legs means that most of their mass ends up crashing right at the height of the windshield of a car. The MDOT advises drivers in the event of an unavoidable collision to aim for the back of the animals so that the driver is not impaled on their antlers, which can grow up to 5ft  across (MDOT, 2015). The economic cost of car damage and infrastructure preventative measures can cost the state large amounts of money.

These collisions between Moose and vehicles occur for a large variety of reasons, most of which is a combination of the original road design in Maine and the needs that Moose have for their habitat. The most common land feature present in a study of moose collisions in New Brunswick Canada was the presence of water features (Christie, 2003). The second and third most common feature over 337 accidents was the presence of limited roads and a trail system. The Maine State Interagency Work Group on Wildlife/Motor Vehicle Collisions also observed that “most sites possessed wetland characteristics” (Maine Interagency, 2001). Moose are very aquatic mammals and have been observed to follow water systems in order to migrate, even swimming long distances (Kauffman, 2020). Therefore it stands to reason that road ways passing by or through waterway systems are at a greater risk of a collision between moose and vehicles, simply because of the movement practices of the moose.

Mitigation taken by the Maine Department of Transportation involves multiple different landscaping techniques to help deter or manage wildlife crossings on already constructed roads. They even have certain techniques that are specific to moose, such as the use of rip rap, or sharp gravelly rocks, along embankments as a deterrent to road crossings  (Holyoke, 2019). This has seen to have some success, as it has been observed that the larger animal’s feet are sensitive to sharp objects. Other techniques involve the use of fencing, under or over passes, reflectors, habitat manipulation (such as the addition of non desirable plants) and chemical repellents. These methods all have their drawbacks, most of which is the cost of installation and/or upkeep. Fences, while very affordable and effective at keeping wildlife out, can actually act as a trap if one manages to make it through. This can cause serious injury to drivers when the animal panics and can also cause further property damage. There is a lack of data on the effectiveness of reflectors on ungulate populations, and more research needs to be conducted in order for any state to consider this low cost strategy. (Maine Interagency, 2001)

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“Fences, while very affordable and effective at keeping wildlife out, can actually act as a trap...”

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Areas such as Banff National Park have benefited greatly from the construction of an animal overpass structure, reducing the amount of accidents along the roads and contributing to a large range of species crossing safely. However, the amount of money that it takes to build and then maintain these types of structures can be prohibitive to many states. There have been few research studies determining the ability to turn old culverts into wildlife under passage ways. One such study that took place in Pennsylvania observed the use of preexisting culverts by white tailed deer. The author determined that as long as the culverts adhered to specific requirements such as keeping the passageways as wide and short as possible - to increase the “openness” of the space - and to make the way reliable in all types of weather, then this strategy would be met with some success (Braudin, 2003). Due to the large size of the moose, standing at an average 5 feet tall at the shoulder, determining the correct size of a culvert to facilitate their use might prove to be a challenge. Particularly since more observational research needs to be conducted to determine the average ceiling height a larger ungulate will tolerate before refusing to enter an enclosed space.

One of the mistakes that states and counties make is to use collision preventative measures based on previous accident reports with the belief that larger amounts of collision areas demonstrate wildlife crossing areas. One article in the Landscape Ecology journal argues against this tactic, citing that the decision of where an animal crosses a road is filled with too many different variables to make this data reliable (Snow et. al, 2014). Indeed the most effective way to determine where to assist in Moose crossing would be to determine their travel corridor and how they interact with the landscape surrounding the roads. Studies that involved tagging Moose movements conducted in the Western part of the US demonstrated the very specific corridors that the Moose used. They were found to be closely related to water and were not deterred by roads (Kaufmann et. al, 2020). This method could be used to determine the best culverts to be converted into wildlife corridors for Moose.

However, the need to conduct such extensive research and take such road safety measures could be fading. The Moose activity in Maine has been dropping for the last twenty years. The amount of moose hit in 2018 (257 collisions) is a dramatic drop from the 1990s, where there were an average of 500 collisions a year (Maine Interagency, 2001). This year the Maine Department of Fish and Wildlife released a statement about how the amount of Moose successfully hunted were down, most likely due to hotter than usual temperatures which restricts the animal’s movements (Warner, 2021). The US Department of Agriculture (USDA) officially changed Maine’s plant zone map in 2012, reflecting the rising temperatures the state has experienced and likely will continue to experience (Hoey, 2012). The Maine Climate Council predicts that the forests will lose most of the spruce-fir forests and will be replaced with more hardwoods such as yellow birch and red oak (Maine Climate Council, 2020). Warmer winter temperatures with a longer spring season means that disease carrying bugs such as ticks will thrive. Winter ticks are a menace to the moose population, who are generally unable to get rid of the excess amount and are known to die from these bugs through both disease and blood loss  (Fernandez et. al, 2020). The Moose’s inability to cope with temperatures in excess of 57°F in the summer, or 23°F in the winter mean that the population will struggle to live in Maine. They will most likely be fading out of the ecosystem in the next few decades.

The sheer amount of plants that Moose survive on, along with their propensity to eat new shoots from burned and ecologically disturbed areas means that a wide variety of plants will not have population management. I predict that other herbivores will step into this role- such as deer- and their own numbers will create a population boom. This is highly problematic because the extinction of wolves during European settlement means that the burden of population management falls solely onto human hunters... and the vehicle-deer collision rate is at least eight times higher than with Moose (Collisions Between Wildlife, 2015). While creating underground culverts specifically for Moose may not have practical applications in the future, continuing this type of project could still benefit other species and keep both drivers and wildlife populations safer.