When a friend recently noted that she had just found a Spotted Salamander (Ambystoma maculatum) in her basement and was wondering if she could release it outside, I was quick to point out that this could be the Salamander’s last walk. The weather was too cold. So just where do these pond-breeding salamanders go during the harsh New England winter?
It wasn’t a question that was easy to answer for biologists until recently. In the spring Spotted Salamanders crawl to vernal pools, temporary woodland ponds that fill with water but then dry out later in the summer and provide a fishless environment for larval salamanders, where they mate and lay eggs. But for 90% of the year they are somewhere in the forest. Sometimes you can find them by flipping over a large stone or rolling a rotting log, but for the most part, they are impossible to find.
Recent technology has allowed biologists to easily spy a Spotted Salamander whenever they want. Miniature tags encased in inert epoxy that emit a radio signal are surgically placed into the body cavity of a Spotted Salamander. After a few days of recovery, the salamander is released where it was captured. All of its movements and locations can then be monitored with a radio receiver and small antenna.
Steve Faccio, a fellow biologist at the Vermont Center for Ecostudies, captured 8 Spotted Salamanders and 8 Jefferson’s Salamanders (A. jeffersonianum) for a study at the Marsh-Billings-Rockefeller National Historic Park in Vermont. He first bathed them in a solution of tricaine methanesulfonate to put them into a deep sleep for the quick operation. Just 24 hours later, they were released near their capture site. A few days later, we were on the hunt.
I have tracked many animals with radio telemetry and they have led me on wild chases that can last for miles. The nice thing about tracking salamanders is that they don’t really go that far and they don’t move that fast, but they can be difficult to pinpoint. They like to go underground where radio signals don’t travel well.
Standing on a forest path near the site, I turned on the radio receiver and tuned to the salamanders frequency. A faint, but audible ping emitted from the headphones. A few minutes later I was in the general area of the animal. The signal was strong, but we just couldn’t quite pinpoint it. He was underground. After an hour on our hands and knees, we found the spot. A series of narrow, branching tunnels under the leaf litter and rotting logs held our prize. We were able to move just a few leaves and there he was peering out at us from a tunnel opening.
All summer long we tracked them to tunnel systems. The salamanders can’t dig. They use shrew, mice and chipmunk tunnels for refuge. In fact, the tunnels are so important to them that Steve could predict areas in the forest that would be used by the salamanders just by the density of mammal tunnels. Without small mammals, there were no salamanders.
After tracking them to these surface tunnels all summer long, suddenly, as the chill of winter was slowly engulfing New England, the salamanders changed behavior. They entered more vertical tunnels that led deeper into the ground. By the end of November nearly all of them were deep under the earth. The radio signal only travels about 2-3 feet. Most signals were lost. They had gone deep enough to escape the ground penetrating frost.
While some amphibians, like Wood Frogs (see http://audubonguides.wordpress.com/2010/02/15/not-too-cold-for-a-frog/), can withstand freezing temperatures, these salamanders cannot. They rely on small mammal tunnels to escape the deep freeze, or a cozy basement.