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Dicamptodon aterrimus - Idaho Giant Salamander

Page history last edited by PBworks 14 years, 2 months ago

Idaho Giant Salamander

Dicamptodon aterrimus





Identification - The Idaho giant salamander is large and robust predator.  The salamander may be brown, purple, grey, tan, or copperish color with a pattern of spots or blotches over body.  It resembles the Tiger Salamander (Ambystoma mavortium) superficially by it's size and shape except for indistinct costal grooves and lack of foot tubercles.  The fourth toe on the hind foot has only three segments.  The head and body is thick.  The average length is between 7 to 11.75 inches long, but have been observed as large as 13 inches. 


Larvae have external gills which are small showing adaptation to living in small streams.  Larve are tan with yellowish blotches over skin.  Most larve become mature adults but some undergo paedomorphosis where they maintain larval form with sexual maturity.


Larvae stage of Idaho giant salamander






Distribution -


In Idaho, these salamanders are found in forested watersheds in north-central Idaho.  From Coeur d'Alene River south to the Salmon River. 

They are also found in two locations in Montana  in Mineral county.





Habitat - Larve inhabit clear, cold streams, and montain lakes and ponds.  Adults can be found under logs, rocks, bark or other debris by mountain streams or rocky shores of lakes.  Damp coniferous forests are likely spot to inhabit and can be seen crawling across the forest floor.  Idaho Giant Salamanders can climb and have been observed up to 8 feet high in vegetation.  They occur as high as 7,000 feet in elevation.  Life expectancy is between 6-10 yrs in the wild, with 3 years until reaching maturity.


Typical habitat for Idaho giant salamanders - Picture taken in Idaho County, Idaho.



 They occur in the same habitat as the tailed frog (Ascapus truei) and is an important prey item for larval salamanders.



Behavior - Feeding behavior in larvae are sit-and-wait predators.  They feed on many small invertebrates and some small vertebrates.  These vertebrates can include fish, tadpoles, and other larval salamanders.  Adults eat terrestrial invertebrates and vertebrates.  They will eat pretty much anything that can catch.  They can eat things as big as small snakes, shrews, mice, and other salamanders. 


Their main predators are fish, garter snakes, weasels, and water shrews.  But they have defense mechanisms that give them a chance to survive.  They secrete toxic substances from their skin, use warning postures, growl or squawk, and bite.  Their bite an easily break human skin.



Reproduction - Water is needed for reproduction.  Breeding occurs in spring and fall in the headwaters of mountain streams.  Courtship probably takes place in nest site were eggs are layed.  Female usually attaches eggs under submerged logs or rocks deep in stream.  Females may lay clutches of 135-200 and guards until eggs hatch after about 9 months.  Eggs are around 6.5 mm in diameter and unpigmented.  Little is known about reproduction process and behavior.




 Hypothetical representation of what eggs would look like.




Taxonomy -


  •  Kingdom Animalia (animals)

  • Eumetazoa (metazoans)
  • Bilateria (bilaterally symmetrical animals)
  • Deuterostomia (deuterostomes)
  • Phylum Chordata (chordates)
  • Craniata (craniates)

  • Subphylum Vertebrata (vertebrates)
  • Superclass Gnathostomata (jawed vertebrates)
  • Euteleostomi (bony vertebrates)
  • Class Sarcopterygii (lobe-finned fishes and terrestrial vertebrates)
  • Tetrapoda (tetrapods)
  • Class Amphibia (amphibians)
    Subclass Lissamphibia (amphibians)
    Order Caudata (salamanders)
  •   Family Dicamptodontidae (Pacific giant salamanders)
  •    Genus Dicamptodon (Pacific giant salamander)
  •   Species Dicamptodon aterrimus (Idaho giant salamander)





Scientific Study


B. C. CARSTENS, J. D. DEGENHARDT, A. L. STEVENSON, J. SULLIVAN (2005) Accounting for coalescent stochasticity in testing phylogeographical hypotheses: modelling Pleistocene population structure in the Idaho giant salamander Dicamptodon aterrimus Molecular Ecology 14 (1), 255–265.


  It studied the genetic differences of the Idaho giant salamander by examining 118 mtDNA sequences in several populations here in Idaho.  One area of study was from the Clearwater drainage and another was from the Salmon River drainage.  The article speculated where and when the possible populations separated from each other and which one was the original population.  Hypothesis testing using geograpical simulations to create null distributions indicates expansion from the Clearwater drainage is improbable but expansion from the South Fork of the Salmon drainage is a possibility.  Data suggested that there may have been two refugias (populations) that entered these drainages.  By testing three a priori hypotheses that predicted both drainages were being utilized during the late Pleistocene, showed that the divergence didn't occur during the Cordilleran glacial maxima (20,000 ybp), Sangamon interglacial (35,000 ybp), or pre-Pleistocene (1.7 mya) time period.  Tests point to recent population expansion (>20,000 ybp) but can’t conclude where.



















Page was written and organized by Shane McKinley

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