by Ryan Morra
April showers bring more than May flowers, and birds aren’t the only creatures producing fantastic choruses in the springtime. While birders will set their alarms for 5:00am in order to catch the rainbow of spring migrants arriving in Vermont, herpetologists – that is, aficionados of amphibians and reptiles – will spend the wee hours of the night up to their knees in muck and water to glimpse the bizarre courtships of frogs and salamanders.
Rain and warmth sets the stage for the drama. Just last week, the temperatures began rising above 50°F and light rains were predicted to start around 7:00pm on Tuesday night. Every herper in the Champlain Valley was on alert. Sure enough, the rains came, and my friends and I descended upon Shelburne Pond, where dozens of others, from child to adult to childlike adult, had also gathered in hopes that this would be a “Big Night,” as we say in herp lingo.
Nearly all amphibians need to keep their skin moist, so they won’t venture out of their over-wintering huddles in the forest until a good rain soaks the leaf litter. The spring snowmelt and rains fill in woodland depressions, creating temporary water bodies – or “vernal pools” – a perfect place for laying eggs without being eaten by fish. Spotted salamanders, blue-spotted salamanders, and wood frogs are the earliest breeding amphibians in Vermont. They will travel up to hundreds of feet from their forest dwelling to court, mate, and lay eggs in these predator-free pools.
Pond Road is a hotspot for viewing amphibians migrating to vernal pools. While these migrations are happening in forests all over Vermont, when a road bisects the forested and wetland areas, it provides an easy way to spot these intrepid travelers. All you need is a good flashlight, rain jacket, and rubber boots.
The chorus of spring peepers was almost deafening in some spots along Pond Road, but in the background we could also hear the clattering of wood frogs, enraptured in their eccentric courtship, known as “amplexus.” The smaller males grab a female from behind (holding on is easy due to his enlarged thumbs) and deposits his sperm as she lays her eggs (if he is the chosen one, of course). In the confusion of the darkness, males will sometimes grab each other in amplexus, in which case the male’s body will vibrate intensely as a way of saying “hey, hands-off me!” You can simulate this effect by holding a male in your hands and very gently squeezing on his sides.
Some spotted salamanders, which are almost cartoon-like in their bulky size and large yellow spots, were still engaging in their own stunning mating orgy in a vernal pool down the road. Male spotted salamanders gather in groups to perform for the females by writhing around each other, bobbing their heads under one another’s tails, and clumping into huge twisting masses known as “congresses.” If a female spots a male she likes, she will accept the offer of his spermatophores (little capsules of sperm bundled together) and take them up into her cloaca. She will then find a nice twig submerged in the water and deposit her fertilized eggs around it.
This was probably one of the last glimpses of spotted salamanders in their group mating, as the window for catching this is narrow, and confined mostly to early spring. Like many other migratory phenomena, amphibians stagger their movement and calling during the season. In higher elevations, you may still see the spotted and blue-spotted salamanders and wood frogs. We realized that last week wasn’t quite a Big Night, because we were right in the middle of two major breeding periods. The cold-tolerant species were finishing up, and the temperatures weren’t quite warm enough for the next round of breeders.
But right now in the Champlain Valley, I am keeping my ears alerted for the low knocking sounds of northern leopard frogs (so called because of their dark spots outlined with a light halo), the high buzzing of gray treefrogs, the deep humming of the American bullfrog, and the singular “gulp!” of the green frog.
Beginning in late May and into early June – look for little tadpoles and tiny gilled salamanders to start swimming around in these ponds. Their challenge is to mature and head for the woods before the pools dry up with the summer heat.
In the meantime – Happy Herping!
Get to know your frog calls at: http://www.pwrc.usgs.gov/frogquiz/
Learn about Vermont’s Reptiles and Amphibians, and submit your findings: http://community.middlebury.edu/~herpatlas/index.html
Ryan Morra is a jack-of-all-trades and soon-to-be Master of Science when he completes the Ecological Planning program this May. He is a high school science teacher, polyglot, cyclist, and forever-developing naturalist with a particular pull towards hepetofauna these days.