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Four-toed Salamanders

Fall Amphibian Migration

10-24-16-red-backed-sal-089The migration of amphibians from the woodlands where they overwinter to their breeding pools in March is a familiar spring phenomenon to most. However, some of these amphibians engage in a fall migration as well. Amphibians (and reptiles) need to find a good overwintering spot, where they won’t freeze. In some cases, that might be a few feet upstream or into a seepage area, and in others it is a few hundred yards uphill. The extent of the migration and the species participating vary in different parts of the state.

In western Vermont, Jim Andrews, Director of the Vermont Reptile and Amphibian Atlas(http://vtherpatlas.org), has observed Blue-spotted and Four-toed Salamanders moving down into wetlands in the spring, staying close to the wetland for moisture and feeding during the summer, and then moving uphill back to wintering areas in the fall. On the other hand, he has found that most Spotted and Jefferson Salamanders, as well as Wood Frogs, move down in the spring to breed, and then head back uphill in stages soon after they are done breeding.

Eastern Red-backed Salamanders (pictured) migrate as needed during the summer to maintain their body moisture, and in the fall, search for an animal burrow or crevice to hibernate in. Migration often occurs at night, while it’s raining, so as to prevent their skin from drying out. (Amphibians need to have moist skin because a large portion of the frog’s “breathing” occurs via oxygen diffusing through the skin. Oxygen will not diffuse through a dry membrane.) After the very dry summer we’ve had, a large number of amphibians were observed taking advantage of the recent rain and migrating.

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“Big Night” Hazard

big night 2016 IMG_7612Every year in early spring on a rainy night spotted, blue-spotted, Jefferson and four-toed salamanders, wood frogs, and spring peepers leave their leaf litter and subterranean winter hibernacula and migrate to their ancestral breeding pools to mate.  Sometimes there are roads between these two sites.  Vehicles driving these roads inevitably kill thousands of salamanders, wood frogs and spring peepers every year.  Concerned citizens have set up teams to try to scoop up these nocturnal travelers and escort them to the side of the road in which they were headed.  While this action definitely helps, it is hard to find enough generous volunteers to man every crossing on every road all through a rainy night.

In Monkton, Vermont, Jim Andrews, Steve Parren and Chris Slesar, along with the Lewis Creek Association and the Monkton Conservation Commission, spear-headed an effort this past year to do something about the mortality of hundreds of migrating frogs and salamanders. Grants, plus a large number of organizations and citizens, provided the manpower and finances to construct two concrete culverts under a road in a location where the road separates the breeding pools of amphibians from their upland wintering grounds.

In the past, hundreds of migrating amphibians were killed in this location by automobiles during every spring and fall amphibian migration, and it is doubtful whether the population would have been able to sustain itself over time. (In the past month, 673 salamanders and 329 frogs have safely passed through the tunnel.  In addition, a few early migrators (16) have already started coming back up hill.) Hopefully, these will be the first of many such culverts in the Northeast. For further information on the Monkton underpasses, go to:  http://www.burlingtonfreepress.com/story/news/2016/03/28/hundreds-saved-new-vermont-salamander-crossing/82336084/.  (photo:  spotted salamander)        

Naturally Curious is supported by donations. If you choose to contribute, you may go to http://www.naturallycuriouswithmaryholland.wordpress.com  and click on the yellow “donate” button.