Wildlife crossings are essential to the survival of wildlife

Laura Lundquist

(Missoula Stream) Three recent scientific studies highlight not only how important wildlife crossing structures are but also that crossing structures are less useful if their design discourages wildlife from using them.

Scientists from the Museum of Natural History of Utah, the University of Ioannina and Northern Arizona University on Wednesday published a study that provides more evidence of the importance of preserving wildlife migration corridors between Glacier and Yellowstone National Parks.

The study has been published in Scientific Reports, an open-access journal published by Nature.

Using data from nine studies conducted across four continents, scientists have developed a theoretical model, an equation that can predict how long before half of the species stuck in an isolated area will go extinct—such as a national park surrounded by human development.

Scientists use the word “relaxation” to refer to the loss of a species over time in a confined area. The time when we lose half of a species is the ‘relaxation half-life’.

Their regression showed, with fairly good accuracy, that the smaller the average number of species within an ecosystem, the faster they are likely to go extinct. Obviously, smaller wildlife refuges will have smaller populations of species.

Using only species of medium- and large-sized ungulates, carnivores, and rabbits, the scientists calculated the relaxation half-lives for Glacier-Waterton and Yellowstone-Teton parks. They then ran the model when the four parks are connected by three migration routes. The scientists also ran the numbers for Mount Rainier National Park to the North Cascades parks in Washington state.

The results showed that groups of species in Montana outlived more than three times as long if they had migratory corridors than if they were restricted to just one park group or the other.

The problem is that Glacier-Waterton and Yellowstone-Teton parks are essentially isolated, mainly because of immigration barriers like railroads and highways. And this isolation gets worse with the increase in human development.

Scientists suggest it’s time to create wildlife migration corridors and keep them open. They also encourage less housing development near national parks.

The nonprofit Yellowstone to Yukon promoted the same.

“Concerted efforts will be required to strengthen the capacity of national parks and related reserves in western North America to maintain healthy plant and animal communities over the next century. Implementing a region-wide program to establish linkages between national parks and related reserves in western North America, including the National Park Yellowstone National Park, the first national park in North America, will significantly enhance the persistence of plant and animal communities in the northern Rocky Mountains and the Falls,” the scientists concluded.

Animal crossing structures, such as bridges or tunnels, can help wildlife cross highways and railways. Previous research along a stretch of the Trans-Canada Highway near Banff National Park in Alberta found that a series of crossing structures reduced total wildlife collisions by 80% while collisions with elk and deer were nearly eliminated.

Twelve years ago, Confederate Salish and Kootenai tribes built 41 such structures across Highway 93. But some of the early efforts may need adjusting, based on some things biologists have reported recently.

In December, scientists from the University of British Columbia published a study in the journal Biodiversity and Conservation that found that most flyways in North America, Europe and Asia are very narrow.

Observations over the past decade show that grizzly bear cubs, cubs, and prey species such as elk avoid very narrow bridges, less than 150 feet wide. However, in a survey of 120 bridges, scientists found that most were not wide enough, averaging only about 100 feet wide. The Animal Trail at Flathead Sanctuary is 197 feet wide.

Then, research from UCLA showed that predators like elk and deer are less likely to use an underpass if they are startled or frightened by passing traffic.

The scientists reviewed 600 animal-activated videos collected by Montana State University road ecologist Anthony Clevenger that showed elk and white-tailed deer near an underpass on the Trans-Canada Highway near Banff National Park.

Videos showed that elk and deer browsing near the tunnel often fled or woke when vehicles passed and were less likely to use the crossing.
Researchers urged highway designers to build animal crossings that protect wildlife from surrounding noise.

“If we can figure out ways to take advantage of wildlife behaviors, we may be able to make wildlife crossings more efficient,” researcher Eric Abelson told Science Daily. For example, walls to dampen sound or reduce the visual effects of passing headlights may encourage the use of crossing structures. We hope this study is only one of many that will examine different wildlife species and traffic levels to better develop tools that increase the use of Transit structures by wildlife, ultimately protecting human and wildlife lives.”

Reporter Laura Lundquist at lundquist@missoulacurrent.com.

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