Friday, May 4, 2007
Biodiversity Corner: Red-Spotted Newt
Name.The red-spotted newt is one of four closely related species of Eastern Newt, all of which have the name Notophthalmus viridescens. The sub-species in our area is N. viridescens viridescens. All newts are in the family Salamandridae which sounds like it should include all salamanders but it is an exclusive club for newts. Our friends the spotted salamanders, Blue-Spotted Salamanders,and Jefferson Salamanders are all mole salamanders and belong to a different family. The term "salamander" is used to describe the order Caudata which includes all the salamander families. So this means that all newts are salamanders, but only some salamanders are newts. This is further confused by the name "eft "which is used for young newts.
When and where seen. Leslie Thomas brought me a Red-Spotted Newt that she found on Bellows Hill Road on April 29. It had succumbed to the hazards of crossing the road. These newts are not classified as rare or threatened at the state level but I had never before seen one in Carlisle. I often see them in the woods in Central and Western Massachusetts. I would very much like to hear from anyone who finds one in Carlisle.
Life cycle. The Red-Spotted Newt has a rather unusual three-stage life cycle. The first stage is fairly normal — a tadpole hatches from the egg. In the second stage, the aquatic gilled tadpole metamorphoses into a land-dwelling air-breathing sexually immature creature called an eft. The third stage occurs one to three years later when the eft returns to the water and metamorphoses again into an aquatic adult. Sometimes they skip the eft stage and go straight from tadpole to adult newt. This would be like a human having the option to skip adolescence.
Identification. The red spots are a good clue. They occur in both the terrestrial eft and the aquatic adult newt. The spots which vary considerably in number and position usually form two lines along the back. A very young eft, recently transformed from a tadpole, is a dull yellowish or reddish brown but soon becomes a striking bright red-orange color. The red spots can still be seen because they are delineated with a black edge. The bright red body color darkens almost to black at the end of the eft stage but the red spots remain. The aquatic adult is olive-green or greenish-brown on the back and yellow on the belly. Red-Spotted Newts are small creatures. There is not much heft to an eft. I tried to weigh Leslie's specimen but it didn't register anything on my kitchen scale; it was a small fraction of an ounce. Efts usually reach no more than three inches in length and the record for an adult newt is five inches.
Food Chain. Red-Spotted Newts eat insects, worms, leeches, frog eggs and tadpoles. They are reasonably safe from predators because their skin secretions are toxic which allows them to co-exist with fish. Spotted Salamanders which don't have this ability require a fish-free habitat and hence their dependence on vernal pools.
References: Roger Conant, Peterson Field Guide to Reptiles and Amphibians; Savannah River ecology lab at the U. of Georgia (go to www.uga.edu and search on Red-Spotted Newt); Virginia Department of Game and Inland Fisheries (www.dgif.state.va.us). Northern Prairie Wildlife Research Center at http://www.npwrc.usgs.gov/resource/herps/amphibid/species/rsnewt.htm
Submissions for the Biodiversity Corner are encouraged from everyone. What are you finding? Send a note to Kay Fairweather at 392 School St, Carlisle MA 01741 or to firstname.lastname@example.org.
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