Notophthalmus viridescens - Red Spotted Newt

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Notophthalmus viridescens viridescens - Red-spotted newts (Salimandridae) 2006-08-06.jpgple.jpg

(Image of red-spotted newt eft, taken from "Hoarded Ordinaries" blog (www.hoardedordinaries.com), by Dr.Lorianne DiSabato, picture taken August 6, 2006)

Description: Red-spotted newts (Notophthalmus viridescens viridescens) are amphibians of the family Salimandridae and can be found in the Northwood's vernal pools or in their terrestrial stage amongst the damp forest of the Northwoods. Red-spotted newts have a fairly complex lifecycle. They begin their lifecycle as eggs and aquatic larva, and metamorphose into their terrestrial stage (efts) from August to November (Butler et.al 2005). Although there is some debate as to how long this terrestrial stage persists, efts typically remain on land for 3-7 years with many individuals spending most of this time as terrestrial juvenilles (however, some larvae have been known to skip the eft stage and turn right into an aquatic adult). It has been found that during the eft terrestrial stage, efts are not nomadic and will typically disperse only to reach suitable habitats or new water bodies. Although efts are nocturnal, in the Northwoods, red spotted newts can be commonly seen during moist days. Red-spotted newt efts are also known as "red efts", which can range in color from a bright orange to a bold red. Red efts also vary in size, from 3-6.8cm long (Kingsbury date unknown). When out for a walk in the Northwoods, it is important to note that efts rarely move about the forest floor unless it is damp or heavily raining. When the weather is dry, efts are more likely to be found amongst wet leaf litter or humus. Efts are also more likely to emerge in temperatures exceeding 12 degrees Celcius, while they are not as likely to come out below 10 degrees Celcius (Healy 1975). Once the efts have lived on land for several years, they migrate to their aquatic breeding sites where they will metamorphose into the aquatic adult stage of their life. Red-spotted newts surprisingly do not develop gills, and instead have lungs in the aquatic life stage. During this time in their life, the newts can also change color from their bright eft colorations to a duller, yellow-brown or green-brown color with yellow underbellies. They also grow bigger than their eft size, and can range from 5-12.2 cm in length. Aquatic adults are seen with several red spots enrobed in black circles on their dorsal surface, and males can be seen with dark spots on their hind legs during the breeding season (Kingsbury date unknown).

Habitat and Range: Red-spotted newts are a sub-species of the eastern newt, and can be found in the eastern and central parts of the United States and Canada. Red-spotted newts are commonly found in New York, Massachutsetts, Maine, Michigan, Ohio, Indiana, Alabama, Georgia, Quebec, New Brunswick and Novia Scotia. All red-spotted newts require clean, permanent or semi-permanent (vernal pools) bodies of water for their aquatic life stages, and nearby areas of damp vegetation. Red-spotted newts can survive in both decidious and coniferous forests (Kingsbury date unknown).

Resource Acquisition: Red- spotted newts are carnivorous. Aquatic newt larvae consume small invertabrates such as beetle larvae, snails, and small macroinvertabrates. Red efts also consume macroinvertabrates, worms and whatever they can scavenge in the leaf litter. Aquatic adults consume macroinvertabrates, and small aquatic larvae such as midge larvae. All lifestages of the red-spotted newt rely on visual cues when hunting for food, and water clarity as well as temperature have a significant impact on the feeding process (Riemland 2000).

Reproduction: Male and female red-spotted newts reach sexual maturity around the age of 3. The breeding season begins in late Winter and lasts until early Spring. During the breeding season, female red-spotted newts carry hundreds of eggs and search for a prospective mate. The courtship ritual of the red-spotted newt adult begins when the female is attracted to the male's spots on his hind legs, as well as the common male behavior of wiggling and fanning his tail whch causes an odor to be released. Once the female has chosen her mate, the male will then deposit a sperm packet on the bottom of the water body, and the female will pick it up, using the sperm to fertilize her eggs. In some cases, males will compete with one another, and in some rare situations, display courtship behaviors towards each other. In other instances, rivaling males will drop their sperm packets to the bottom of the water body despite the fact that the female already has a male sperm donor, in which case the female may pick up that male's sperm packet by accident. Once the female's eggs are fertilized, she will only lay a few eggs per day, and it is unclear whether she will lay all of her eggs during the breeding season. The female will then deposit her eggs on vegetation, and leave them forever. Eggs will hatch after 3-8 weeks, but this varies based on environmental conditions (Riemland 2000).

Dispersal: Although red-spotted newts typically do not disperse far during their lifecycle, red efts will disperse from their parents' water bodies, and sometimes seek new water bodies. Some scientists speculate that the efts' dispersal behavior (preference for new water bodies) is based on efts utilizing new water bodies formed by beavers. Once the eft metamorphoses into its aquatic adult stage, the newt will remain in the selected water body for the rest of its life (Ford & Johnson date unknown).

Defenses and Natural Enemies: Red-spotted newts have several natural predators such as leaches (preying on newt larvae and ectoparasites on aquatic adults), frogs, turtles, birds and fishes. However, the red-spotted newt defends itself by secreting a toxin (indicated by its bright warning coloration) which to fishes and birds is distasteful and/or deadly. In a study conducted by Dwight A. Webster of Cornell University on the toxicity of the spotted newt, Mr. Webster found that out of several hundred brook tout examined in a study period of 10 years, not a single fish had ingested a newt. Scientists still speculate whether the rejection of the aposematic prey (newt) is a learned behavior, and if so, how the behavior is learned (Webster 1959). It is also important to note that while the handling of red-spotted newts will not harm humans, if a newt is handled, it is encouraged that hands should be promptly washed, as the red-spotted newt has been indicated as a carrier of the Salmonella bacteria. Interestingly, red-spotted newts (mainly larvae), have also been found as the prey of the Northern Pitcher Plant (Sarracenia purpurea), a carnivorous plant often found in nutrient-poor bogs accross the eastern United States and Canada. Although the pitcher plant normally aquires its nutrients through the breakdown of trapped insects, red-spotted newt larvae have also been found among the cup-like holds of the pitcher plant. In a study conducted on red-spotted newts as a nutrient source for pitcher plants, J.L Butler, et.al, found multiple trapped red-spotted newt larvae which may have been deposited in the pitchers when the plants were underwater or the newts were attracted to the plants as a source of protection from predators. Butler et.al also speculates that the newt larvae could have been attracted to the pitcher as a food source due to the insects trapped within the pitcher (Butler et.al 2005). Ultimately, all of the larvae observed died, most likely due to the low pH of the pitcher water, as amphibians in general are extremely susceptible to acidic conditions.

Threats to Red-spotted Newts: Although the red-spotted newt is still common throughout the eastern United States and parts of Canada, habitat fragmentation, wetland destruction, forestry operations, and acid deposition all have serious negative imlications for the red-spotted newt. As the red-spotted newt requires both water and land close to that water body, it is critical that we conserve wetland and forested areas such as the Northwoods, for the continued success of the red-spotted newt.

Related species (congeners) in Northwoods: Despite the fact that the red-spotted newt has quite a few relatives, none of them live within the Northwoods. The red-spotted newt's closest relations are the other eastern newt sub-species, ((the central newt (N.v. louisianensis), peninsula newt (N.v. piaropicola), and the broken-striped newt (N.v. dorsalis)). The eastern newt (which contains the red-spotted newt as a sub-species) is also closely related to the striped newt (N.pestriatus) which is found in Georgia and Florida (USGS 2006).


References:

  • Butler J.L, Atwater D.Z & Ellison A.M (2005) Red-spotted Newts: An unusual nutrient source for Northern Pitcher Plants, Northeastern Naturalist 12:1-10
  • Healy W.R (1975) Terrestrial activity and home range in efts of Notophthalmus viridescens, American Midland Naturalist 93:131-138
  • Webster D.A (1959) Toxicity of the spotted newt (Notophthalmus viridescens) to trout, Copeia 1:74
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