The Carlisle Mosquito Online

Friday, April 4, 2003


Blue-spotted/Jefferson Hybrid Salamander

Photo by Tom Wilson
Name: A hybridization between the Blue-spotted salamander (Ambystoma laterale) and the Jefferson salamander (Ambystoma jeffersonianum). Both these species of salamanders are threatened; each is designated a "species of special concern" by the Massachusetts Division of Fisheries and Wildlife. Salamanders in the genus Ambystoma are called mole salamanders because the adults spend most of their lives out of sight burrowed under forest debris like rotting logs, or in small mammal burrows.

When and where seen: This one was seen by Tom Wilson on March 29, 2003, as it crossed Evergreen Lane. These are rare creatures and the best chance of seeing one is on a wet night in early spring when the nighttime temperatures are above freezing. This is when the salamanders return to their natal pool for breeding. Mole salamanders may live up to half a mile from the pool and have to cross roads to return making them vulnerable to inadvertent killing by motorists.

Characteristics: Blue-spotted salamanders are up to 5.5 inches long and generally black or grayish-black and sprinkled with small blue spots, while Jefferson salamanders are up to 7.5 inches long and tend to be brown with fewer blue or gray spots on the body. The hybrid salamanders are somewhere in between; usually more brown than black and with less prominent spots.

Where have all the guys gone? Most of the hybrid salamanders are females. Their methods of reproduction are not fully understood. Many have an extra set of chromosomes and require sperm only to trigger egg development, not to contribute genetic material. The hybrid species is dependent on males from one of the parental species.

Life cycle: Eggs are laid in vernal ponds in early spring; the embryos hatch within 4 to 6 weeks; the larvae live in the pond for 2 to 4 months before metamorphosing into adults and moving ashore.

Habitat: Mole salamanders are dependent on vernal pools for breeding, egg-laying and larval stages of their life cycle. For the rest of the year they live in forested wetlands and just beneath the forest floor within a half mile of a vernal pool.

Habitat protection: There is a certification program for vernal pools in Massachusetts run by the Natural Heritage and Endangered Species Program. It documents the existence of vernal pools so they may then be afforded protection from irresponsible development through several regulations. If you would like to have a vernal pool certified, you can get more information from the Carlisle Conservation Commission at 1-978-369-0336.

References: University of Michigan Museum of Zoology at;; Leo P. Kenney and Matthew R. Burne, A Field Guide to the Animals of Vernal Pools (the Carlisle Conservation Commission has these field guides on order.)

2003 The Carlisle Mosquito