Every spring there comes a day when the temperature approaches or exceeds 45 degrees, and a gentle spring rain occurs and extends into the night.* These conditions signal the impending nocturnal migration of many amphibians to their breeding pools. Spotted Salamanders, Jefferson/Blue-spotted Salamanders, Wood Frogs, Spring Peepers and an occasional American toad rise from their state of hibernation to crawl out of the dirt and make their way to wetlands (often vernal pools) where they will breed and lay their eggs. So many migrate en masse that the first night that this migration takes place has been dubbed “Big Night.”
It goes without saying that in many cases, roads have to be crossed when going from hibernaculum to breeding pool. This poses a major threat to the frogs and salamanders that are on the move, and roads often become slick with their carcasses due to unwitting automobile drivers. If you are out driving on the first warm, wet evening this spring, drive slowly while keeping an eye out for lumps in the road, and if you see them and have a flashlight or head lamp handy (to find the frogs and salamanders, as well as to announce your presence in the road to other drivers), stop and lend them a hand (usually there are concentrated areas where crossings occur). (Perhaps a group of well-marked volunteers could gather to monitor and assist migrating amphibians at major road-crossing locations in your town.) It should be obvious which direction the frogs and salamanders are all headed in, and they can be placed well off that side of the road. (Photo: left to right, Wood Frog, Spring Peeper, Spotted Salamander)
*With one to two feet of snow on the ground and vernal pools still frozen over in many parts of northern New England, this event will most likely not occur with the impending warm, rainy weather, but will happen in the next few weeks.
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Vermonters were witness to a record-breaking (early) amphibian migration in the Champlain Valley last week on March 1st, when night temperatures were in the low 50’s. Not only did it occur a week earlier than any other previous major migration, but records show that migration for the earliest amphibians in Vermont is now approximately two to three weeks earlier than it has been during the last decade. (as reported by Jim Andrews, www.VtHerpAtlas.org).
Spotted Salamanders, Four-toed Salamanders, Eastern Red-backed Salamanders, Blue-spotted Salamanders, Jefferson Salamanders, Spring Peepers, Wood Frogs and even an American Toad were on the move. According to Andrews, “this is a concern if the weather turns really cold and the ground and ponds refreeze. If that happens, many of the early migrants (that are not freeze tolerant) could freeze and die. If the weather stays relatively mild, with only short cold snaps, they should be fine.” Weather since these sightings has been unseasonably cold, and one can only hope they survived. (Photo: Spotted Salamander, Ambystoma maculatum)
The 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.
Every 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)
With spring peepers (pictured) and wood frogs just coming into voice, and some salamanders also having recently emerged from hibernation, there is concern for their welfare due to the erratic weather we are having. According to Jim Andrews, Director of the Vermont Reptile and Amphibian Atlas, the effects of this meteorological fluctuation depend on the exact climatic conditions experienced, as well as the species affected.
Wood frogs and spring peepers, as stated in a recent post, are well equipped to survive the cold weather. However, egg-laying has already taken place in some locations and if the eggs are exposed to the air, as opposed to being attached to a submerged branch or vegetation, and it’s cold enough, long enough, they will freeze.
Many of the mole salamanders, including spotted, Jefferson, and blue-spotted, are in the middle of migrating to or from their annual breeding pools. Faced with freezing temperatures, they retreat temporarily into the leaf litter and thawed soil beneath, a sheltered environment where they spend all of their life except the breeding season. An extended period of cold that freezes the ground would pose problems for these creatures, although Andrews has witnessed the survival of a blue-spotted salamander that sought shelter under rocks that were on top of frozen ground.
Many factors are involved in the effects of this phenomenon – how warm it was before the cold spell arrived (long enough for hibernating amphibians to emerge?), how low temperatures go, how long it remains cold, the species of frog or salamander, and where it is in its breeding cycle. The peeping and quacking we briefly enjoyed has been silenced, but not permanently and hopefully not for very long.