With the weather finally starting to show the first hints of winter, most reptiles and amphibians are settling down into their winter hibernation. Under the ice in certain vernal pools, however, one species stays active all winter long: marbled salamanders! These attractive striped amphibians have an unusual life-history strategy that sets them apart from many of the other vernal pool denizens that live in New England. Vernal pools, which only exist for part of the year and therefore have no fish in them (fish being full-time water users, for the most part), are vital breeding grounds for many amphibians. After the dry of summer and the cold of winter, frogs, toads, and salamanders of many species take advantage of the first spring rains that refill the vernal pools to breed and lay their jelly-like egg masses.
Marbled salamanders (above) take a different approach. They breed during the fall, and the female finds a shallow depression or dip in the terrain that is dry to lay her eggs. The eggs have a tough coating that prevents them from drying out and allows the larvae to begin developing, but the water-breathing young salamanders can’t finish their hatching process until their nursery fills with water. When the rains (or, in some cases, the snows) come, the rising water level induces the marbled salamander eggs to hatch. The larvae then begin feeding and growing in the cold pools during the fall and winter, when most other amphibian species are in hibernation!
At Zoo New England, our interest in these fascinating creatures is more than just academic. The Middlesex Fells, a beloved conservation and recreation area spanning over 2500 acres adjacent to our own Stone Zoo, used to be a stronghold for marbled salamanders. Unfortunately, they disappeared from the Fells during the mid-20th century, casualties of a rapidly changing landscape that interfered with the delicate balance of mature forest and seasonal wetlands that the salamanders need in order to thrive. Since 2016, the ZNE Field Conservation team has been working with local schools to raise and reintroduce young marbled salamanders to this protected area. Those young salamanders are gathered as newly-hatched larvae in the fall and winter from a healthy source population in western Massachusetts.
Recently, our team paid that source population a visit to check out some vernal pools we hadn’t previously visited. In order to survey a vernal pool, we sweep the water with nets to catch what’s swimming in the water column, and transfer the catches to glass or plastic trays for identification (See image at right). Each pool gets several passes in likely-looking spots to ensure good coverage before we move on to the next pool.
The survey yielded several interesting finds, including fingernail clams (small, freshwater relatives of ocean clams, pictured to the left) and some adult eastern newts – another species of salamander that is aquatic both as a larva and as an adult, but has a bright orange terrestrial “teenage” phase called the red eft.
We didn’t find any marbled salamanders on this trip, but the exceedingly wet late summer and fall of 2021 may have made it hard for females to find a dry depression in which to lay their eggs. We’re not giving up the search for this year’s salamanders, and any larvae we bring in to headstart will be sure to appear here on the blog for your viewing pleasure.