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.
A magical migration awaits all who take note of the first rainy spring day (in the 40’s) when the rain continues into the night. Last night these conditions resulted in what herpetologists refer to as “Big Night.” While snow still covers parts of the forest, there is ample bare ground that has warmed up enough to waken hibernating frogs and salamanders at this time of year. As if silently communicating with each other, thousands and thousands of these amphibians emerge from their subterranean hibernacula on the very same night and migrate en masse to their ancestral breeding pools, known as vernal pools. They avoid the lethal sun by travelling at night, in the rain. Unfortunately, many die, as they often must cross hazardous roads in order to reach the pool where they breed every year. If you are driving in these conditions, please keep an eye out for these jaywalkers and try to avoid them. Roads can quickly become slick with their squashed bodies.
How many Spring Peepers, Wood Frogs and Spotted Salamanders can you find in this photograph taken on Big Night? (There are six.) Thanks to the unbelievable generosity of Naturally Curious readers, this photograph was taken with my new camera and lens. I cannot tell you how deeply touched I am by your kindness and generosity.
Naturally Curious is supported by donations. If you choose to contribute, you may go to https://naturallycuriouswithmaryholland.wordpress.com and click on the yellow “donate” button.
This is the time of year when vernal pools become a main attraction for certain breeding amphibians and invertebrates. Most of these ephemeral wetlands, due to evaporation and transpiration, dry up during part of the year and therefore cannot support a population of fish. This makes them a highly successful breeding environment for creatures that need water in which to reproduce, for both they and their eggs stand a much better chance of surviving without predatory fish.
Vernal pools attract certain species of amphibians and invertebrates that are completely dependent upon these pools for parts of their life cycle (obligate species). In much of the Northeast these include wood frogs, spotted salamanders, blue-spotted and Jefferson salamanders, marbled salamanders (southern N.E.), eastern spadefoot toads (southern N.E.), vernal fairy shrimp (southern N.E.) and knob-lipped fairy shrimp (northern N.E.). If you discover a woodland body of water that has one or more of these species breeding in it, you have found what is technically referred to as a vernal pool. (Photo insets clockwise: Wood Frog, upper right; Blue-spotted Salamander by E. Talmage; Spotted Salamander)
The next Naturally Curious post will be on 4/18/17.
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)
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.
A few short weeks ago spotted salamanders gathered at vernal pools to breed and lay eggs. Since then their eggs have started hatching, and gilled spotted salamander larvae can now be found in these pools. The larvae are major predators and consume many insects and crustaceans, including mosquito larvae and fairy shrimp. During the next two or three months, these larvae will develop lungs, absorb their feathery gills and begin life as terrestrial amphibians, assuming the temporary pools they are in don’t dry up prematurely.
After male spotted salamanders emerge from hibernation and arrive at their ancestral breeding (vernal) pools, they cluster in groups called congresses, await the arrival of females, pair up with one and then the pair performs a courtship dance.
Unlike some species of amphibians, the male spotted salamander does not fertilize the eggs as the female lays them. Rather, she collects his sperm into her body and internal fertilization takes place. When the female is sufficiently stimulated, the male deposits up to 80 spermatophores (pyramid-shaped plugs of mucus with a sperm capsule at the top), often on a submerged branch. The male maximizes the chances of insemination by depositing many scattered spermatophores, covering every spermatophore he encounters, even his own, with a new spermatophore. In so doing, he increases his spermatophore count, while simultaneously eliminating a rival’s spermatorphores. The female then crawls over a spermatophore and positions her vent, or cloaca, so as to allow the lips of her cloaca to detach the sperm capsule.
Within a short period of time the salamanders retreat back to the woods, rarely to be glimpsed until next spring’s breeding season. (Photo: spotted salamander spermatorphores, with sperm capsule missing on far left spermatophore)
It’s rare to get a glimpse of a Spotted Salamander – these secretive amphibians spend most of their lives hidden under rocks or logs or in the burrows of other forest animals, emerging only at night to feed and during spring mating. In central Vermont, the annual mass migration of Spotted Salamanders to their ancestral breeding pools began two nights ago, when the rain-soaked earth and rising temperatures signaled that it was time to emerge from hibernation. Unfortunately for the salamanders (and frogs) that answered the calling, temperatures dropped relatively early in the evening, and the rain turned to snow. Undaunted, these stout salamanders continued their trek through the woods, plowing their way through new-fallen snow, all in the name of procreation.
Red Foxes have a very diverse diet – birds, small mammals, snakes, frogs, eggs, insects, fish, earthworms, berries, fruit — the list is endless and this diversity is part of the reason that foxes thrive in almost any habitat. However, the fox whose tracks I was following recently passed up a meaty meal – that of a Spotted Salamander. The story the tracks tell suggests that the fox dropped the salamander after unearthing it from its hibernaculum and carrying it some distance. It’s likely that it had detected the sticky white toxic liquid that Spotted Salamanders secrete from poison glands in their skin when they are threatened. Unfortunately, detection did not occur in time to save the salamander’s life. Either its experience with the fox and/or freezing temperatures killed the salamander, preventing it from going back into hibernation. (Note red fox tracks to right of salamander.)