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Taricha granulosaRough-skinned Newt

By Amanda Lorenz

Geographic Range

Taricha granulosa is found along the Pacific coast of North America, with a range extending from Santa Cruz County, California, south of San Francisco Bay, into southeastern Alaska north to Juneau. Within this range, it is found at elevations from sea-level to 2743 m, or 9000 ft, and is found on many islands off the coast, including Vancouver Island. In northern California rough-skinned newts are found as far east as Shasta County, extending into northern Butte County. Isolated populations of T. granulosa occur in Latah County, Idaho and Saunders County, Montana. The Idaho population, at least, is probably introduced. ("Native Amphibians--Introduction", 2007; Behler and King, 1979; Jones, et al., 2005; Petranka, 1998)

Habitat

Taricha granulosa inhabits both aquatic and terrestrial environments. Though they generally spend more of their time on land, they must return to the water to breed. Many become temporarily aquatic during the summer months due to dry weather. It is possible for a newt to spend its entire life in an aquatic habitat. In the water, T. granulosa prefers areas of little or no current, such as ponds, lakes, and slow-moving streams, and sometimes small ephemeral wet areas such as ditches. Aggregations of adults have been discovered as deep as 12 meters underwater. On land, newts can usually be found under pieces of rotting wood on forested hills or mountains. They occasionally occur in open areas such as fields. (Bishop, 1943; Jones, et al., 2005; Petranka, 1998)

  • Aquatic Biomes
  • lakes and ponds
  • rivers and streams
  • temporary pools
  • Range elevation
    0 to 2743 m
    0.00 to 8999.34 ft
  • Range depth
    0 to 12 m
    0.00 to 39.37 ft

Physical Description

The eggs of T. granulosa are each separately encased in a gelatinous substance, around 3 to 4 millimeters in diameter. The ova are generally light-brown on top and cream colored on the bottom. (Jones, et al., 2005)

Larvae are aquatic, with a faint dorsal stripe on either side of the body that fades as they mature. Larvae have a dark stripe that extends from the eye to the nostril as well as two rows of spots. One row is near the limb insertions and the other is near the fin. The fin is speckled with dark spots. Larvae measure around 18 mm in total length. (Jones, et al., 2005; Petranka, 1998)

Adults range from about 12.7 to 21.6 cm in total length. They have rough, grainy skin that is dark-colored dorsally and orange to yellow-orange ventrally. Their textured skin has earned them the common name "rough-skinned newts." Their eyes are relatively small and do not extend beyond the edges of the head. The irises are yellow, and the lower eyelids are orange. The vomerine teeth are arranged in a V-shaped pattern. Costal grooves are absent. Males are larger than females, with longer vents. During the breeding season, males and females become temporarily aquatic. Males develop smooth, spongy skin that is lighter-colored than usual. Their vents are strongly pronounced and swollen. The tail crests become more pronounced, as do the nuptial pads on the tips of their toes. The appearance of the females does not change, though their vent becomes cone-shaped. (Behler and King, 1979; Jones, et al., 2005; Petranka, 1998)

Some adults living at high elevations retain their gills and are totally aquatic, though they do not exhibit genuine paedomorphosis. Aquatic females can sometimes be confused with breeding males, because they have lighter, smoother skin, tail crests, and larger vents than do terrestrial females. However, these features are less pronounced than in breeding males. (Jones, et al., 2005; Petranka, 1998)

  • Sexual Dimorphism
  • male larger
  • sexes shaped differently
  • Range length
    12.7 to 21.6 cm
    5.00 to 8.50 in

Development

Taricha granulosa exhibits an aquatic larval stage. Eggs hatch 3 to 4 weeks after being laid, and these newts spend 4 to 5 months as aquatic larvae before metamorphosing into juvenile adults. In some high elevation areas, newts overwinter as larvae and emerge in the spring or summer. They spend a couple of years as juvenile adults before returning to the water to breed. At high elevations, some adults retain their gills and spend their entire life cycle in the water. Adults reach sexual maturity at 4 to 5 years of age. (Jones, et al., 2005)

Reproduction

Breeding takes place underwater, and is initiated by the male. He climbs on top of the female, clasps her with his legs, and proceeds to rub the snout of the female with his chin while stroking her legs with his hind legs. This behavior is known as amplexus, and can last anywhere from several hours to two days. The male then releases the female, crawls in front of her, and deposits a spermatophore, which is a gelatinous mass with a small capsule of sperm at the top. The female picks up the sperm capsule with her cloaca (vent). In some instances other males will attempt to separate an amplexed pair. (Petranka, 1998)

Reproduction in T. granulosa is totally aquatic, usually occurring in still or slow-moving waters near vegetation. The breeding season is highly variable depending on elevation. At lower elevations, most reproductive activity occurs in the spring, from January to May. At high elevations, most breeding occurs during late summer and early fall. Females lay their eggs soon after mating. The eggs are laid one at a time and are attached by the female to vegetable matter or detritus. They take 3 to 4 weeks to hatch. (Behler and King, 1979; Jones, et al., 2005; Petranka, 1998)

  • Breeding interval
    Rough-skinned newts breed annually or biennially, depending on their location.
  • Breeding season
    At high elevations most breeding occurs during late summer, while at lower elevations most breeding occurs during the spring months.
  • Range time to hatching
    3 to 4 weeks
  • Range age at sexual or reproductive maturity (female)
    4 to 5 years
  • Range age at sexual or reproductive maturity (male)
    4 to 5 years

There is no parental care exhibited by this species. The female takes care to attach her eggs to vegetation so they will not float away and provides nutrients for development. (Petranka, 1998)

  • Parental Investment
  • no parental involvement
  • pre-fertilization
    • provisioning
    • protecting
      • female
  • pre-hatching/birth
    • provisioning
      • female

Lifespan/Longevity

Little is known about the longevity of T. granulosa, but marked specimens have been recaptured after 17-18 years. (Ridenhour, et al., 2007)

  • Range lifespan
    Status: wild
    18 (high) years

Behavior

Adult T. granulosa usually spend some portions of their lives in terrestrial habitats and some portions in aquatic habitats. They are known to migrate to and from mating sites, possibly using celestial cues as well as olfaction to navigate. Diurnality and nocturnality vary according to population. Rough-skinned newts produce a powerful toxin, tetrodotoxin, from granular glands located in the skin. The amount of toxin per newt varies geographically, with some regions bearing newts with extreme toxicity and some regions with newts of low toxicity. When provoked, rough-skinned newts will display the unken reflex, in which the head is bent back and the tail curled up to expose the animal’s bright-colored belly as a warning to potential predators. (Jones, et al., 2005; Petranka, 1998)

Home Range

Not much is known about territory size, but aquatic adults seem to prefer shallow water during the beginning of the year (spring) and deeper water during the latter part of the year.

Communication and Perception

It is unclear how T. granulosa individuals communicate with one another, but there is evidence that rough-skinned newts navigate using celestial cues, olfaction, and darkened areas caused by vegetation at the edges of water bodies. (Jones, et al., 2005; Petranka, 1998)

Food Habits

Larvae eat small aquatic invertebrates. Aquatic adults have been known to eat a variety of organisms, from snails and insects to other amphibians. (Petranka, 1998)

Adult terrestrial T. granulosa appear to be opportunistic carnivores, with insects making up a large portion of their diet. (Packer, 1961)

  • Animal Foods
  • amphibians
  • insects
  • terrestrial non-insect arthropods
  • mollusks
  • zooplankton

Predation

Because of the extreme toxicity of rough-skinned newts, they have only one known predator, common garter snakes (Thamnophis sirtalis), which seem to be immune to tetrodotoxin. It has been proposed that these two species are competing against each other in an evolutionary arms race, in which a predator species and a prey species co-evolve, each developing greater defenses against the other. In this case, as the newts evolve greater toxicity, garter snakes evolve greater resistance to the toxicity. (Brodie III and Brodie Jr., 1990)

Ecosystem Roles

Since T. granulosa is mainly an insect eater, it is important in keeping insect populations in check, possibly including some nuisance insect species, such as mosquitoes (Culicidae). Taricha granulosa is also an important food source for common garter snakes, which are in turn eaten by other animals. (Brodie III and Brodie Jr., 1990)

Economic Importance for Humans: Positive

Taricha granulosa is of particular interest to biologists because of its evolutionary arms race relationship with common garter snakes. This species is also exploited for the pet trade.

  • Positive Impacts
  • pet trade
  • research and education

Economic Importance for Humans: Negative

There are no known adverse effects of T. granulosa on humans, unless ingested. These newts contain enough toxin to kill several humans. (Brodie III and Brodie Jr., 1990)

Conservation Status

Rough-skinned newts are not listed as threatened or endangered, but like many amphibian species may face such a distinction if their habitat is extensively threatened by human development.

Contributors

Tanya Dewey (editor), Animal Diversity Web.

Amanda Lorenz (author), Michigan State University, James Harding (editor, instructor), Michigan State University.

Glossary

Nearctic

living in the Nearctic biogeographic province, the northern part of the New World. This includes Greenland, the Canadian Arctic islands, and all of the North American as far south as the highlands of central Mexico.

World Map

agricultural

living in landscapes dominated by human agriculture.

aposematic

having coloration that serves a protective function for the animal, usually used to refer to animals with colors that warn predators of their toxicity. For example: animals with bright red or yellow coloration are often toxic or distasteful.

bilateral symmetry

having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.

carnivore

an animal that mainly eats meat

chemical

uses smells or other chemicals to communicate

diurnal
  1. active during the day, 2. lasting for one day.
ectothermic

animals which must use heat acquired from the environment and behavioral adaptations to regulate body temperature

fertilization

union of egg and spermatozoan

forest

forest biomes are dominated by trees, otherwise forest biomes can vary widely in amount of precipitation and seasonality.

freshwater

mainly lives in water that is not salty.

heterothermic

having a body temperature that fluctuates with that of the immediate environment; having no mechanism or a poorly developed mechanism for regulating internal body temperature.

insectivore

An animal that eats mainly insects or spiders.

internal fertilization

fertilization takes place within the female's body

introduced

referring to animal species that have been transported to and established populations in regions outside of their natural range, usually through human action.

iteroparous

offspring are produced in more than one group (litters, clutches, etc.) and across multiple seasons (or other periods hospitable to reproduction). Iteroparous animals must, by definition, survive over multiple seasons (or periodic condition changes).

marsh

marshes are wetland areas often dominated by grasses and reeds.

metamorphosis

A large change in the shape or structure of an animal that happens as the animal grows. In insects, "incomplete metamorphosis" is when young animals are similar to adults and change gradually into the adult form, and "complete metamorphosis" is when there is a profound change between larval and adult forms. Butterflies have complete metamorphosis, grasshoppers have incomplete metamorphosis.

migratory

makes seasonal movements between breeding and wintering grounds

molluscivore

eats mollusks, members of Phylum Mollusca

motile

having the capacity to move from one place to another.

mountains

This terrestrial biome includes summits of high mountains, either without vegetation or covered by low, tundra-like vegetation.

natatorial

specialized for swimming

native range

the area in which the animal is naturally found, the region in which it is endemic.

nocturnal

active during the night

oviparous

reproduction in which eggs are released by the female; development of offspring occurs outside the mother's body.

pet trade

the business of buying and selling animals for people to keep in their homes as pets.

poisonous

an animal which has a substance capable of killing, injuring, or impairing other animals through its chemical action (for example, the skin of poison dart frogs).

polygynandrous

the kind of polygamy in which a female pairs with several males, each of which also pairs with several different females.

riparian

Referring to something living or located adjacent to a waterbody (usually, but not always, a river or stream).

seasonal breeding

breeding is confined to a particular season

sexual

reproduction that includes combining the genetic contribution of two individuals, a male and a female

solitary

lives alone

suburban

living in residential areas on the outskirts of large cities or towns.

temperate

that region of the Earth between 23.5 degrees North and 60 degrees North (between the Tropic of Cancer and the Arctic Circle) and between 23.5 degrees South and 60 degrees South (between the Tropic of Capricorn and the Antarctic Circle).

terrestrial

Living on the ground.

visual

uses sight to communicate

zooplankton

animal constituent of plankton; mainly small crustaceans and fish larvae. (Compare to phytoplankton.)

References

2007. "Native Amphibians--Introduction" (On-line). Alaska Department of Fish and Game. Accessed December 01, 2007 at http://www.sf.adfg.state.ak.us/statewide/ngplan/files/Amphibians.pdf.

Behler, J., F. King. 1979. National Audobon Society Field Guide to North American Reptiles and Amphibians. New York: Alfred A. Knopf, Inc..

Bishop, S. 1943. Handbook of Salamanders: The Salamanders of the United States, Canada, and of Lower California. Ithaca, NY: Comstock Publishing Company, Inc..

Brodie III, E., E. Brodie Jr.. 1990. Tetrodotoxin resistance in garter snakes: an evolutionary response of predators to dangerous prey. Evolution, 44/3: 651-659.

Jones, L., W. Leonard, D. Olson. 2005. Amphibians of the Pacific Northwest. Seattle, WA: Seattle Audobon Society.

Packer, W. 1961. Feeding behavior in adult Taricha . Copeia, 1961/3: 351-352.

Petranka, J. 1998. Salamanders of the United States and Canada. Washington and London: Smithsonian Institution Press.

Ridenhour, B., E. Brodie Jr., E. Brodie III. 2007. Patterns of genetic differentiation in Thamnophis and Taricha from the Pacific Northwest. Journal of Biogeography, 34: 724-735.

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