The Great Salamander Migration

Next Generation Science Standards: 

  • MS-LS2-2.Construct an explanation that predicts patterns of interactions among organisms across multiple ecosystems.
  • MS-ESS3-3. Apply scientific prinicpales to design a method for monitoring and minimizing human impact on the environment.

Key Vocabulary: vernal, ecosystems, migration, indicator species, habitat, photosynthesis

Salamanders Article Guide

In the early spring rain just after temperatures start to rise from the 40s into the 50s, several species of salamander and other amphibians can be seen crawling along the Midwestern forest floor to vernal pools in mass migration.

Much like salmon traveling upstream to reach traditional breeding grounds, these amphibians will move towards shallow, seasonal pools to lay eggs, reproduce, then skitter back into their forest burrows, rarely to be seen again. From our human perspective, it appears as though the forest floor has become a creeping, hopping, slithering mass of previously unseen creatures converging onto a single point. But for the salamanders, it is the start of a season, a moment to reproduce, then return back to their comfortable homes in the woods. The season itself does not last long, just February, March, and April, but within that time these salamanders run a gauntlet of interested citizen/scientist, human roads, souvenir ‘pet’ collectors, environmental toxins, and even pools that were present last season but have since disappeared due to human development.

Temporary, or vernal, pool from March (left) and June (right). Pools such as the one shown above are the destination of salamanders in the spring. Why might these be desired breeding grounds for salamanders?. Photo Credit: (National Park Service 2016)

A Common Salamander with an Uncommon Ability

While the number of salamanders migrating along the forest floor in the early spring is large, there are only a handful of salamander species that migrate in the early spring. Among the most common in Northeast America are the Spotted Salamander and the Jefferson Salamander.

Secretive, shy, and nocturnal, the Spotted Salamander and the Jefferson Salamander can be difficult to find outside of their migratory season. Called ‘Mole’ salamanders, their skin is wet and slimy to the touch and they spend most of the year underground in cool, moist burrows which protect them from freezing temperatures during the winter. Spotted Salamanders are also, curiously, the only known vertebrate (animal with a spine) to photosynthesize within their body. It is noticeable in the embryonic stage where a single-celled alga co-exists within the cells of the spotted salamander embryo to create oxygen for the respiration of the embryonic salamanders. This peculiar relationship is still being investigated.

From left to right; Spotted Salamander and Jefferson Salamander (Photo Credit: James Crumpler)

The Curious Citizen/Scientist

As the salamanders move from the forest to their vernal pools, one of the first obstacles they might meet is citizens and scientists. In order to survey salamander populations and gauge the relative health of an ecosystem (typically using a metric called the Index of Biotic Integrity, IBI), scientists will create a blockade around these vernal pools of one-foot high netting with drop buckets every 10 feet or so. As the salamanders move from forest to the pools, they run into the netting, move along it, then drop into the shallow buckets. During each night of the migration months, a survey team, will walk along the netting and take the salamanders and other amphibians from their bucket and record data of the number, sex, and type of salamander then release them into the pools they were attempting to reach.

These survey counts, when taken year after year, provide detailed information about the lives of salamanders in an area. The timing of migration, the number of salamanders in an area, which species are in an area, and whether the population is mostly male or female can all be used to determine the relative influence of human or environmental impacts within an ecosystem.

Threats

Even though the Spotted Salamander and Jefferson Salamander are common in the Northeast United States, salamander and amphibian populations are generally in decline. Such declines are deeply concerning; as an indicator species of ecosystem health, their loss would seem to correspond with continued environmental loss and degradation.

Their sensitive skin makes them particularly prone to changes within an ecosystem, which in turn may indicate the relative health of an ecosystem. An oil spill at the Oak Glen Nature Preserve in Hamilton County, Ohio flooded a nearby creek with 21,000 gallons of crude oil, turning the stream black.

As part of the ongoing restoration efforts in the Oak Glen Nature Preserve area, a 10-year salamander survey is being used as one of many indicators for the effectiveness of the cleanup. The presence of salamanders in the area may indicate at least a marginal return ecosystem to normalcy after the oil spill event.

Roads and other human development tend to be the most destructive ongoing events to salamander populations. Salamanders that cross roads to reach vernal pools are often crushed by oncoming traffic. In one example, on Rio Mills and Polo Grounds roads in Charlottesville, Virginia, the mortality rate for Spotted Salamanders on migration night was roughly 50%. These rates have since gone down as volunteers, during migration season, stop traffic and help move Spotted Salamanders, and other amphibians, from one side of the road to the other.

Miami University researchers gather salamanders during their migration to capture critical data on local ecosystems (Photo Credit: James Crumpler)

Vernal pools, which are necessary to salamander reproduction, are often drained and surrounding forests cleared in order to make room for new farmland or other human development. These pools have disappeared at an alarming rate, and the quality of rebuilt vernal pools and wetlands has been called into question; however, the tools available for siting rebuilt quality wetlands is improving with better mapping technology.

The interconnectedness of ecosystems makes determining cause and effect relationships between species very difficult to ascertain. As salamander populations rise and fall, the salamander acts as the canary in the coal mine, offering early warning of danger or safety ahead. Taking care “to keep every cog and wheel is the first precaution of intelligent tinkering” as Aldo Leopold once stated, and human tinkering in the natural world is expansive. Since every part of an ecosystem is connected, it is dangerous to remove one piece without understanding how it is connected to the next. Too much tinkering within an ecosystem may ruin its function.

Collectors

Familiarity with amphibians as a child often sparks a healthy interest in the environment. Images of splashing around a creek searching for tadpoles, frogs, snakes, and other creatures are often the early introductions of many successful careers in science.

A healthy love and appreciation for nature may also lead to well-intentioned but ultimately destructive practices by some. In Cleveland, the Great Brecksville Salamander Migration, at Valley Parkway between Chippewa Creek Drive and Deer Lick Cave in Brecksville, has recently been protected by Cleveland Metropark staff, but, for a time was habitually raided by “a group of a dozen children with adult leaders who were gathering up salamanders in two large buckets…” who would “come every year and gather salamanders to give to our children and neighbors for pets” according to a Metropark staffer who spoke with the collectors. The desire to motivate curiosity and provide in-house specimens for observation is good, but it must be balanced with the knowledge that these are wild creatures that can only thrive in the wild. These salamanders are bad pets as they do not like to be handled, prefer to live underground, and can be illegal to possess in some states. Personal stories of salamanders are more likely to flourish outside the home than as a pet.

What you can do to protect salamanders

Although it may not seem like much, protecting these creatures can be pretty easy. If you are on the road at night in February-April, keep an eye out of salamanders crossing the road. You can even pick up the salamander and move them from one side of the road to the other. Stop people from collecting salamanders as pets, and protect local wetlands and vernal pools. The first step to protection is learning more about these fascinating creatures from teachers, friends, parks, and first-hand experience!

Salamander migrations are not like the Wildebeest migrations of the Serengeti. Nor are they like the great bird migrations that take place each fall and spring. They occur in pockets, around the country, usually moving no more than a few hundred yards to wetland pools that only last for a season; however, they are an incredibly interesting phenomenon, and, unlike a Wildebeest or bird, can be encountered and handled one on one and face to face.

This article was written with the help of Jason Bracken, an amphibian researcher at Miami University in Ohio, who provided the pictures, the brief movie, and additional insights into the lives of salamanders in Ohio.  Thanks Jason!

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