Amphibian Migration: A Big Night Surprise

Audrey Kropp Wednesday, 17 March 2021

4.3/5 rating (3 votes)

A little over ten years ago, my partner and I bought our first home on 16 acres of wooded land bounded on the interior by a lovely unnamed tributary to the Hannacrois Creek in the headwater region. The property had key features I valued as a biologist and nature lover of a rural setting, rich in natural forest cover and that lovely stream. Little did I know, our new home and property was the setting of a fascinating biological phenomenon.

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The shallow rectangular “pond” that sat 50 feet or so outside our door appeared to be an abandoned excavation for the house foundation or could have been a relic of the sheep farming history of the land. Whatever it was, our somewhat unattractive swamp now serves as a breeding pool for hundreds if not thousands of spotted salamanders and wood frogs.

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I made the discovery on the first rainy night in April. I was sitting on the front porch relishing temperatures warm enough for rain, thinking of spring.

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Shortly after noticing a yellow spotted salamander chilling out in a nest spruce next to me, my partner came to tell me he had seen several in the driveway. Coincidentally, I began my career at a biological field station working on forest ecology research projects studying salamanders and the detrital (leaf litter) food web. I donned my raincoat and boots, grabbed my flashlight, and began piecing it together. The property was swarming with yellow and Jefferson-blue salamanders as well as wood frogs.

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After noticing the direction they were all headed, I found myself at the edge of the “pond” witnessing the migration and mating of mole salamanders referred to as “Big Night”. Yellow spotted salamanders, Jefferson-blue salamanders and wood frogs are all amphibians that migrate to breed in fishless woodland pools in the spring. Their skin must remain moist to survive so they live in burrows under rocks and rotting logs and spend most of their time on the forest floor under leaves and moss. During the winter they hibernate and emerge on rainy nights in late March and early April when the ground has thawed with nightly temperatures above 40F.

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With the necessary conditions met, they begin a journey to the woodland pool that their predecessors have and their offspring will use to mate. This generally occurs on a select few to one night in spring called “Big Night”. The males arrive at the pools first, commencing the mating process by forming and writhing in large balls called congresses. When the females arrive, the males break off and perform a courtship dance to entice the females to a sperm packet he deposited earlier on the floor of the pool. If agreeable, the female will follow, pick up the packet and fertilize her eggs internally. The female then lays egg clusters in large gelatinous masses on submerged vegetation in the pool. Then everyone disperses back into the forest for another year.

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The journey these salamanders and frogs take to produce generations to come can reach distances of more than a quarter of a mile. In making the migration, they often encounter roads and driveways they must cross. Unfortunately, many of these slow-moving animals are killed during migration due to the fragmentation of forest and wetland habitat from human development. In an effort to reduce this mortality and better understand the issue, the NYS DEC developed the Amphibian Migrations and Road Crossings Project. This project enlists volunteers to find locations where migrations cross roads; document weather and traffic conditions; record migrating amphibians; and help them across the road. Many folks help independently on their own property and take care to look out for a variety of creatures along roadways—including volunteers who are helping migrating amphibians to cross these treacherous obstacles safely.

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I was aware of this migration event from my experience in forest ecology, but after witnessing it first-hand, I was awestruck by this wondrous phenomenon. These salamanders and frogs are important links in forest food webs and indicators of healthy, functioning ecosystems. Each spring, I watch the weather closely, wagering when it will be “the night”. On those nights, our family limits our vehicular travel and goes about ushering our fellow beings off the road and driveway. We all can help to keep our neighbors and amphibian friends safe in this way and by spreading the word about the springtime migration. You can find additional resources on the Amphibian Migrations and Road Crossings website through the NYS DEC: https://www.dec.ny.gov/lands/51925.html

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Comments (1)

  • Van Fleet

    Van Fleet

    02 April 2021 at 11:03 |
    Amazing that this happens right in your backyard. I was curious about these congresses of male salamanders and found this great YouTube video showing the phenomenon. https://www.youtube.com/watch?v=v9eQNFiRPnM Thank you for sparking my interest.

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