ORONO, Maine — Massachusetts native Kristine Hoffmann feels right at home in her wading boots in vernal pools in Orono.
As a youngster, she enjoyed exploring a spring wetland close to her Bay State backyard. And these days, vernal pools — forest floor depressions that fill with water in the spring and generally dry out in late spring or early summer — are again an interest for Hoffmann.
The University of Maine doctoral student is studying the breeding ecology, habitat selection and life histories of the blue-spotted salamander (Ambystoma laterale), including the distance they emigrate from vernal pools. Hoffmann recently followed one salamander 280 meters from a local vernal pool, multiple times the distance she anticipated.
“When I saw this job, it felt like coming home,” Hoffmann said of her dissertation research. “It’s a great opportunity.”
In recent years, vernal pools have become a topic of discussion and concern due to a worldwide decline of amphibians, some of which breed in the vernal pool in which they were born.
In order for blue-spotted salamanders to be conserved, Hoffmann says vernal pools and the adjacent forestland need to be protected. When vernal pools and the critical land around them are destroyed, amphibians are lost, biodiversity decreases and food availability for other species is compromised.
Current Maine regulations state that “the basin depression of ‘significant’ vernal pools must not be disturbed,” said Hoffmann, “and at least 75 percent of the critical terrestrial habitat within 250 feet of the high-water mark must remain intact and forested, with native understory and woody debris.”
Those regulations, though, protect fewer than 25 percent of Maine vernal pools, and Hoffmann said that might not be enough to ensure long-term conservation of other salamanders, as well as wood frogs and fairy shrimp that also breed in vernal pools in the state. Hoffmann said data from her research may inform proposed legislation about zones of consultation in Maine.
Because vernal pools don’t have inlets or outlets and because they dry up, salamanders are at risk from fewer predators than they would be in ponds and lakes. But there’s a trade-off of sorts — they’ve had to adapt to breed quickly — they arrive early to the pool and hatch and undergo metamorphosis within weeks. The impetus is strong — they have to lose their gills and grow lungs before the seasonal pool is gone.
After blue-spotted salamanders grow lungs, they spend much of their life underneath leaves in the surrounding moist woodlands in eastern central North America, the Atlantic Provinces and northern New England. The nocturnal amphibians with long tails can grow as long as 5.5 inches.
Seven days a week, Hoffmann treks to several Orono-area vernal pools. She dons a broad hat, blue jeans and long sleeves to ward off mosquitoes — a staple of salamanders’ diet.
In a sun-dappled forest near a pollen-coated vernal pool Hoffmann checks whether the adult salamanders she implanted with radio transmitters have moved. If they have, she marks the new spots with flags then notes environmental factors including canopy density and soil temperature and moisture level.
Hoffmann implanted the transmitters — which emit signals for about 45 days — during a short surgery in which the salamanders were anesthetized in a UMaine lab. In mid-June, Hoffmann was awaiting the first of this year’s juvenile salamanders to emerge from the pools.
Much of what she’s learned from the research has resulted in more queries. For instance, she questions why after the mass spring migration there were 700 female salamanders and just three males in one area pool.
There are now two types of blue-spotted salamanders, Hoffman said — Ambystoma laterale and unisexual salamanders, which are the result of prior hybridizing. Today, the unisex salamander steals sperm from the Ambystoma laterale. Hoffmann is studying both blue-spotted salamanders and unisex salamanders to see what effects genotype (different genetic compositions), female body size and environmental factors have on egg mass structure and fertility.
She’ll also examine whether environmental factors — pond depth, canopy density, distance to roads and presence of other breeders in the pool — impact breeding site selection. And she’ll explore whether juvenile habitat choice differs between the genotypes.
“We keep finding out things. We’ve found salamanders with three genomes or four or five genomes,” she said, wondering aloud what that might mean for the salamanders’ health and life expectancy. “If we [humans] get one extra chromosome, we get Down syndrome.”
UMaine undergraduates Eleanor D’Urso from Branford, Conn., Catherine Herr from Cape May, N.J.. and Ian Lookabaugh from Lubec are assisting Hoffmann with the research. D’Urso and Lookabaugh are fifth-year wildlife ecology majors and Herr is a fifth-year student majoring in wildlife ecology and mathematics.
Katherine Sypher, an Orono High School junior also assists with the study through the OHS-University of Maine Summer Research Experience Program. The program seeks to increase high school students’ science, technology, engineering and mathematics (STEM) skills.
Sypher says it’s an ideal summer job — she’s paid to work outside while learning and applying practical knowledge.