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Dicamptodon aterrimusIdaho Giant Salamander

By Taylor Michelitch

Geographic Range

The Idaho giant salamander (Dicamptodon atterrimus) is native to northern Idaho and a small westerly portion of the neighboring state of Montana. There is also a smaller population outside of the main range that lives in a more southern area of Idaho. This population lives by Warm Lake in Idaho within the Salmon River. (IUCN SSC Amphibian Specialist Group, 2014; Petranka, 1998)

Habitat

The habitat of the Idaho giant salamander is in the forests of northern Idaho and western Montana. Within these wooded areas, it lives in the small streams and marshy areas. The adult can can be found outside of the water near the streams living under rocks and logs, while the aquatic larvae will be located in streams that are at an estimated elevation of above 975 m. The depth of which it resides in has not yet been recorded. The adult will live under fallen logs and rocks within and along the streams and marshes. The adult female will lay its eggs under completely submerged logs and rocks and remain near this location until larvae reach adulthood. The elevation of where it lives has not been recorded, other than the elevation of its larvae. (Bury, 2004; IUCN SSC Amphibian Specialist Group, 2014; Mullen, et al., 2010; Sepulveda and Lowe, 2009; Sepulveda and Lowe, 2011)

  • Aquatic Biomes
  • rivers and streams

Physical Description

The Idaho giant salamander grows to 170-250 mm in length. The adult has a spotted or mottled color pattern with colors varying from brown, tan, copper, and even grey. Both sexes share the same color pattern and cannot be identified as male or female just by color. The head and body are very thick in comparison to other species of giant salamanders. It has a vertically flattened tail. It has three normal toes on the front feet and then a forth toe on its back feet.

The larval form is 50-180mm before metamorphosing, It has red bushy external gills so that it can breathe under water. It has a less distinct coloring than that of an adult with hints of blue or grey. It lacks the molted pattern of adults. It is born in a tadpole state and the front two limbs are the first to form. The rear dorsal fins form its hind limbs during metamorphosis. When its metamorphosis is complete and lungs are fully developed, this salamander becomes more terrestrial than aquatic instead of the fully aquatic lifestyle as a larvae.

The post-metamorphosis stage is a darker pattern than the adults. Upon reaching adulthood, coastal grooves are obvious. The adults will have 10-13 grooves on the body. Mass in the Idaho giant salamander has not yet been recorded. (Larson and Dimmick, 1993; Mullen, et al., 2010; Petranka, 1998; Sever, 1991)

  • Sexual Dimorphism
  • sexes alike
  • Range length
    170 to 250 mm
    6.69 to 9.84 in

Development

The Idaho giant salamander begins its process of development as soon as its egg is laid by the mother. After hatching from this egg it proceeds to the larval state. Larvae remain in this stage for 6-11 months before metamorphosing into its adult, sexually-mature form. In wild populations, adults be terrestrial or employ a strategy of neoteny, in which adults are still aquatic. It's been reported that the same location can have both types of adults in the population.

The first couple weeks to about 6 months out of the egg will be supervised by the mother and the larvae (with external gills) will be completely aquatic. After this time it will be completely independent. Once metamorphosis is complete, it will continue to grow until it reaches sexual maturity. (Carstens, et al., 2005a; Carstens, et al., 2005b; Good, 1989; Lannoo, 2005; Larson and Dimmick, 1993; Mullen, et al., 2010; Nussbaum, 1983; Nussbaum, 1985; Nussbaum, 1987; Petranka, 1998)

Reproduction

Reproduction for the Idaho giant salamander can occur in the spring , in May, and in the fall in October. Mating is polygynandrous meaning that both the male and females will experience different mates throughout their lifespan. Lacking obvious physical differences between sexes, the methods of courtship and attraction have yet to be determined. All that is known is that mating occurs on the under-side of logs or rocks in the water and fertilization for the species is internal. (Carstens, et al., 2005b; Nussbaum, 1983; Nussbaum, 1985; Nussbaum, 1987; Petranka, 1998)

Mating with the Idaho giant salamander can occur in May or October. Due to the prolonged female investment in the eggs and larvae it will only alternate its time of reproduction each year while the male can reproduce both times of the year. After mating the female will lay between 130-200 eggs. She will lay these eggs underwater in a small pool under a rock or submerged log. The eggs hatch after 6-7 months. After hatching from the eggs it will take the larva 3-6 months to become independent. During this time period the female is still present to protect the larvae. Both sexes complete their metamorphosis at about 1-2 years of age and will not reach sexual maturity until 3-5 years of age. Birth mass of this species is yet to be recorded. (Nussbaum, 1983; Nussbaum, 1985; Nussbaum, 1987; Petranka, 1998)

  • Breeding interval
    Idaho Giant Salamanders can breed in two different times of the year if they did not reproduce within the other timeframe.
  • Breeding season
    Eggs are laid within the months of May and October.
  • Range number of offspring
    130 to 200
  • Range time to hatching
    6 to 7 months
  • Range time to independence
    3 to 4 months
  • Range age at sexual or reproductive maturity (female)
    3 to 5 years
  • Average age at sexual or reproductive maturity (female)
    4.5 years
  • Range age at sexual or reproductive maturity (male)
    3 to 5 years
  • Average age at sexual or reproductive maturity (male)
    4.5 years

After laying eggs, the mother Idaho giant salamander will remain with her eggs to protect them from predators and other male salamanders. Male salamanders of the genus Dicamptodon have been recorded to have cannibalistic tendencies with eating unattended eggs. The female will remain with her young until about 3-4 months after they hatch. At that point they will be considered independent. (Nussbaum, 1983; Nussbaum, 1985; Nussbaum, 1987; Petranka, 1998)

  • Parental Investment
  • female parental care
  • pre-fertilization
    • protecting
      • female
  • pre-hatching/birth
    • provisioning
      • female
    • protecting
      • female
  • pre-weaning/fledging
    • provisioning
      • female
    • protecting
      • female
  • pre-independence
    • provisioning
      • female
    • protecting
      • female

Lifespan/Longevity

The lifespan of Dicamptodon aterrimus is unknown at this time. There have been predictions that it could live as long as 6-10 years in the wild. The most common factor that would affect their population would be predation and the chytrid fungus Batrachochytrium dendrobatidis. This species is not known to be kept in captivity. (Nussbaum, 1983; Nussbaum, 1985; Nussbaum, 1987; Petranka, 1998)

Behavior

Other than during the mating season, the Idaho giant salamander is a very solitary species. This species remains tied to water in its lifetime. It is not an aggressive species, and will retreat at the sight of any potential threat. If handled, though, it will be able to deliver a painful bite due to its larger jaw compared to other species. It is both nocturnal and diurnal. Social behaviors of the Idaho giant salamander are largely unknown. The only commonly known interaction within the species is mating, mating behaviors are unstudied. (IUCN SSC Amphibian Specialist Group, 2014; Metter, 1963; Petranka, 1998; Sever, 1991)

Home Range

Its home range is between 50 and 400 meters squared often tied to its aquatic habitats. A territory has not been reported. (IUCN SSC Amphibian Specialist Group, 2014; Metter, 1963; Petranka, 1998; Sever, 1991)

Communication and Perception

There is little information on communication and interactions with the environment in Idaho giant salamanders. Being an elusive species only one clutch of eggs has actually been found. Nobody has actually seen the mating rituals of this species or how it attracts its mates. There is no proof if it uses pheromones to reproduce or if it attracts mates by other methods. Clearly, it uses vision to perceive its environment. This salamander like many other species of salamanders, is able to "hear" without the presence of ears through vibrations from the environment. This species may be vocal at times. When in danger, some species in this family will make a barking or squawking noise to ward off predators. (Hetherington and Lombard, 1983; Nussbaum, 1983; Nussbaum, 1985; Nussbaum, 1987; Petranka, 1998; Ross and Smith, 1979; Sepulveda and Lowe, 2009)

Food Habits

The Idaho giant salamander is an omnivorous animal. It can often be found eating small insects such as mayflies (Order Ephemeroptera). This species also consumes arachnids, young snakes, small mammals, and small pieces of branches and other assorted plants. It has even been known to eat small tadpoles of their own species. The type of food depends on the individuals size and stage of life. If it is a younger smaller salamander it eats smaller insects and plants. If it is a fully grown adult it will eat much larger insects, arachnids, other larval organisms of its species, and even snails. (Lannoo, 2005; Metter, 1963; Petranka, 1998)

  • Animal Foods
  • amphibians
  • insects
  • terrestrial non-insect arthropods
  • mollusks
  • Plant Foods
  • wood, bark, or stems

Predation

To avoid predation, Idaho giant salamanders have extremely slimy skin that prevents predators from getting a firm grip. This slimy layer also has a toxic substance that can be harmful for a predator to ingest. This salamander also has the ability to bite any threats. In some cases it is reported that when in danger some species in this family will make a barking or squawking noise to ward off predators. Potential predators of this salamander include freshwater fish, and the common garter snake Thamnophis sirtalis. An assortment of small mammals are also predators, including members of the weasel family and the common water shrew Sorex palustris. (Nussbaum, 1983; Nussbaum, 1985; Nussbaum, 1987; Petranka, 1998)

Ecosystem Roles

The Idaho giant salamander plays a very important role in the temperate forest ecosystem. It potentially contributes to the control of the local insect population by using them as a primary food source. This species falls prey to many for many smaller mammals and snakes such as common garter snakes (Thamnophis sirtails) and water shrews (Sorex palustris). They are also host to the parasitic chytrid fungus (Batrachochytrium dendrobatidis). (Feldman, et al., 2002; Sepulveda and Lowe, 2011)

Commensal/Parasitic Species
  • Chytrid fungus Batrachochytrium dendrobatidis

Economic Importance for Humans: Positive

There are no known positive economic effects of Dicamptodon aterrimus on humans.

Economic Importance for Humans: Negative

There are no known negative economic effects of Dicamptodon aterrimus on humans.

Conservation Status

Dicamptodon aterrimus is a species of "Least Concern" on the IUCN Red List. The US Federal List, the CITES appendices and the State of Michigan List do not list this species. Its population still has not been fully estimated. Due to recent changes in habitat and health conditions such as logging and the chytrid fungus, the population of this species is predicted to decline. It is a rapid spreading fungus that kills amphibian populations around the country. This species is susceptible to habitat loss by the clearing of forests and encroaching human populations. (Bury, 2004; IUCN SSC Amphibian Specialist Group, 2014; Sepulveda and Lowe, 2009)

Contributors

Taylor Michelitch (author), Radford University, Cari Mcgregor (editor), Radford University, Zeb Pike (editor), Radford University, Karen Powers (editor), Radford University, April Tingle (editor), Radford University, Jacob Vaught (editor), Radford University, Tanya Dewey (editor), University of Michigan-Ann Arbor.

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

acoustic

uses sound to communicate

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

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

female parental care

parental care is carried out by females

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.

herbivore

An animal that eats mainly plants or parts of plants.

insectivore

An animal that eats mainly insects or spiders.

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.

molluscivore

eats mollusks, members of Phylum Mollusca

motile

having the capacity to move from one place to another.

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.

polygynandrous

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

seasonal breeding

breeding is confined to a particular season

sedentary

remains in the same area

solitary

lives alone

tactile

uses touch to communicate

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

References

Bury, R. 2004. Wildfire, fuel reduction, and herpetofaunas across diverse landscape mosaics in northwestern forests. Conservation Biology, 18/4: 968-975.

Carstens, B., J. Degenhardt, A. Stevenson, J. Sullivan. 2005. Accounting for coalescent stochasticity in testing phylogeographical hypotheses: modelling pleistocene population structure in the Idaho giant salamander Dicamptodon aterrimus. Molecular Biology, 14/1: 255-265.

Carstens, B., S. Brunsfield, J. Demboski, J. Good, J. Sullivan. 2005. Investigating the evolutionary history of the pacific northwest mesic forest ecosystem: hypothesis testing within a comparative phylogeographic framework. Evolution, 59/8: 1639-1652.

Feldman, S., J. Wimsatt, E. Green. 2002. Chytrid detection by PCR: A preliminary study. Proceedings of the American Association of Zoo Veterinarians, None: 312-314.

Good, D. 1989. Hybridization and cryptic species in Dicamptodon (Caudata: Dicamptodontidae). Evolution, 43/4: 728-744.

Hetherington, T., R. Lombard. 1983. Mechanisms of underwater hearing in larval and adult tiger salamanders ambystoma tigrinum. Comparative Biochemistry and Physiology Part A: Physiology, 74/3: 555-559.

IUCN SSC Amphibian Specialist Group, 2014. "Dicamptodon aterrimus" (On-line). The IUCN Red List of Threatened Species e.T59078A64037881. Accessed January 26, 2016 at http://www.iucnredlist.org/details/59078/0.

Lannoo, M. 2005. "Dicamtodon atterimus Idaho Giant Salamander" (On-line). AmphibiaWeb. Accessed April 30, 2016 at http://amphibiaweb.org/cgi-bin/amphib_query?where-genus=Dicamptodon&where-species=aterrimus&rel-genus=equals.

Larson, A., W. Dimmick. 1993. Phylogenetic relationships of the salamander families: an analysis of congruence among morphological and molecular characters. Herpetological Monographs, 7/1993: 77-93.

Metter, D. 1963. Stomach contents of idaho larval Dicamptodon. Copeia, 1963: 435-436.

Mullen, L., H. Woods, M. Schwartz, A. Sepulveda, W. Lowe. 2010. Scale-dependent genetic structure of the idaho giant salamander (Dicamptodon aterrimus) in stream networks. Molecular Ecology, 19/5: 898-909.

Nussbaum, R. 1983. Catalogue of American Amphibians and Reptiles. St. Louis, Missouri: Society for the Study of Amphibians and Reptiles.

Nussbaum, R. 1985. The Evolution of Parental Care in Salamanders. Michigan: University of Michigan Museum of Zoology.

Nussbaum, R. 1987. Parental care and egg size in salamanders: An examination of the safe harbor hypothesis. Researches on Population Ecology, 29/27: 27-44.

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

Ross, R., J. Smith. 1979. Detection of substrate vibrations by salamanders: eight cranial nerve activity. Canadian Journal of Zooology, 57/2: 368-374.

Sepulveda, A., W. Lowe. 2011. Coexistence in streams: Do source-sink dynamics allow salamanders to persist with fish predators?. Oecologia, 166/4: 1043-1054.

Sepulveda, A., W. Lowe. 2009. Local and landscape-scale influences on the occurrence and density of Dicamptodon aterrimus, the Idaho Giant Salamander. Journal of Herpetology, 43/3: 469-484.

Sever, D. 1991. Comparative anatomy and phylogeny of the cloacae of salamanders (Amphibia: Caudata). I. Evolution at the family level. Herpetologica, 47/2: 165-193.

Steele, C., B. Carstens, A. Storfer, J. Sullivan. 2004. Testing hypotheses of speciation timing in Dicamptodon copei and Dicamptodon aterrimus (Caudata: Dicamptodontidae). Molecular Phylogenetics and Evolution, 36/1: 90-100.

Weisrock, D., L. Harmon, A. Larson. 2005. Resolving deep phylogenetic relationships in salamanders: analyses of mitochondrial and nuclear genomic data. Systematic Biology, 54: 758-777.

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