(written by Mark Erelli)
The mole salamanders belong to the family Ambystomatidae, and are represented in the New England region by four main species: the spotted salamander (Ambystoma maculatum), the blue-spotted salamander (A. laterale), the Jefferson salamander (A. jeffersonianum), and the marbled salamander (A. opacum). Herpetologists have long debated about the taxonomic status of blue-spotted and jefferson salamanders. Both are now recognized as their own species, although it is thought that they evolved into two species when populations of a common ancestral species were separated by glaciers during the last Ice Age. After the glaciers melted, the two species came into contact again and interbred, producing hybrids with three or four sets of chromosomes ("triploid" or "tetraploid", as opposed to organisms with two pairs of chromosomes referred to as "diploid"). These hybrids are difficult to tell apart from jefferson and blue spotted salamanders, without performing genetic analyses. Blue spotted salamanders are generally blue-black and sprinkled with small blue spots, while Jefferson salamanders tend to be more brown with fewer blue or gray spots on the body. In contrast, both the yellow spotted and marbled salamanders are easy to identify. Spotted salamanders are distinguished by two dorsal rows of big yellow spots. Marbled salamanders have bands of white, grey, or silver on their backs.
Mole salamanders get their name from their subterranean habits (they are commonly found in underground tunnels and burrows produced by small mammals), and their ability to burrow under rocks, logs, moss, and other vegetative debris. It is here they spend their days foraging for a variety of invertebrates, ranging from earthworms to snails to both larval and adult insects. Most of the year, these stout-bodied animals are quite secretive and are unlikely to be seen unless you are actively searching for them. Fortunately for the naturalist who seeks to observe the habits of these secretive and fascinating creatures, there are certain times during the year when it is possible to observe these animals in high numbers.
In early spring, when the snow is melting, the ground is thawing out, and nighttime temperatures edge above freezing, mole salamanders make their migrations on rainy nights to ephemeral and permanent woodland pools where they congregate in large numbers to breed (note: marbled salamanders are the only species of mole salamander in our area which migrate to breeding pools in autumn). These migrations occur primarily on rainy nights, and individuals may migrate to woodland pools from as far as 120 m away, and tend to return to the ponds where they were born. These pools are usually dry for a portion of the year, thus insuring the lack of fish which prey upon salamander eggs and larvae, and fill up with spring rains, snow melt, and rises in the water table (hence the term "vernal" pool). Anyone who has not witnessed such a migration will most certainly be amazed by the scale of the phenomenon, which may involve hundreds of salamanders. Once in the ponds, the males will leave their spermatophores on the pond floor, where they will be picked up by the female and used to fertilize her eggs. Eggs are laid in masses which range from the size of golf balls to that of tennis balls, depending upon the species.
Salamander eggs are surrounded by a matrix of jelly, which distinguishes them from frog egg masses in which single eggs are merely clustered together. These eggs will hatch in four to seven weeks, and larvae will feed on small invertebrates in the pond until they metamorphose and move onto land in the autumn.
Spring migrations of mole salamanders are a fascinating and awe-inspiring event, for both children and adults alike. These migrations, however, can put salamanders in danger. During migration, salamanders may have to cross roads which have been made through wetlands or forests and can be run over by unsuspecting motorists. In addition, the small, ephemeral pools in which they breed might be regarded as "insignificant puddles" and filled in by developers or homeowners. You can help mole salamanders by being alert for migrations across roads when driving on rainy nights in early spring. Massachusetts also has a certification program run by the Natural Heritage and Endangered Species Program, which alerts the state to the existence of a vernal pool and provides information which may be used by the state to prevent irresponsible development in and around ponds which mole salamanders use for breeding.
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Hunter, M. J., J. Albright, and J. Arbuckle (editors). 1992. The amphibians and reptiles of Maine. Maine Agricultural Experiment Station Bulletin 838. 188 pp.
Kenney, L. P. 1995. Wicked big puddles: a guide to the study and certification of vernal pool. Vernal Pool Association. 58 pp. plus appendices.
Pfingsten, R. A., and F. L. Downs (editors). 1989. Salamanders of Ohio. Ohio Biological Survey Bulletin New Series Vol. 7 No. 2. 315 pp.
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