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Opinion: Amphibian crossings are working

I was the consulting herpetologist for the design and implementation of the two amphibian underpasses in Monkton. The amphibian underpasses in Monkton were the first in Vermont but amphibian underpasses had already been built in all the states and provinces that adjoin Vermont and they have been built for decades in Europe. We in Vermont had the benefit of learning from the strength and weaknesses of those designs. Still, we monitored those underpasses carefully this spring using two different methods and will continue to monitor them in future years.
Using cameras in each underpass set to take photos every minute from dawn to dusk starting on March 10 and running through May 3 this spring, the two underpasses successfully facilitated a minimum of 2,208 amphibian crossings in that time period. During appropriately wet and warm nighttime conditions a steady flood of amphibians were directed through the two culverts by the retaining walls with as many as a dozen crossing through each at one time. Toward the end of that time period, amphibians were both coming and going from the Huizenga Swamp as early arrivals were headed back up into the woods and latecomers were still arriving.
Although I was confident the culverts were designed and placed appropriately, I was still both thrilled and relieved to have my hopes confirmed by the film footage. Although the cameras are not currently monitoring amphibian passage, young amphibians are still moving out of the swamp and some of the adults will stay near the swamp and move uphill only as fall approaches. One of the many amphibian species that these culverts were put in place for were the unusual Blue-spotted Salamanders that were being killed in large numbers every spring on the road surface. Adults of this species only visit the swamp to lay their eggs and then move onto land almost immediately afterward. There are a couple more common species of salamanders (Eastern Newt) and frogs (Green Frogs) that not only remain in the swamp over the summer but they will overwinter there as well.
Although the primary target species group at the Monkton site were amphibians, the underpasses were designed to allow movement of small- to medium-sized mammals as well. So far, our cameras have documented mice, chipmunks, gray squirrels, raccoons, Virginia opossums, eastern cottontails, porcupines and bobcat also using the two Monkton underpasses. Amphibians (and other wildlife) die on roads in many areas of the state, but it would not make fiscal or ecological sense to try to place underpasses at all those locations.
Locations of wildlife crossings must be carefully prioritized based on a wide variety of factors including the rarity of the species involved, diversity and abundance of species using the site, degree of mortality of wildlife at the site, driver safety in the case of larger mammals, the amount of connectivity gained, and of course the cost. Wildlife crossings have already become part of the accepted fabric of transportation design in North American and Europe, hopefully they will soon be familiar to all of us.
James Andrews
Salisbury

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