Idaho Giant Salamander - Dicamptodon aterrimus
Adults have light or tan bronze marbling on a dark brown or black background. They are heavy-bodied, with a large head and muscular legs; body length varies from 3.5 to 8 inches. Larvae are identified by their short, bushy, external gills, their large size, a dorsal fin starting at or behind the rear limbs, and their stream habitat. Other larval salamanders found in Montana live in ponds, have long, feathery gills, and a dorsal fin originating far forward of the rear legs.
No other salamander will be found as an inhabitant of streams in Montana. Eggs are somewhat oblong, large (20-30 mm), and attached on a short pedicle to the substrate in moving water. Terrestrial adults of Long-toed and Tiger Salamanders are much smaller; adult Idaho Giant Salamanders reach a total length up to 340 mm, or 3-4 times that of other salamander species in Montana.
Western Hemisphere Range
Summary of Observations Submitted for Montana
Number of Observations:
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Map Help and Descriptions
(Observations spanning multiple months or years are excluded from time charts)
Known to occur up to 2160 m in elevation (Nussbaum et al. 1983). Transformed adults, although seldom seen, inhabit moist coniferous forests where they may be found under logs, bark, or rocks. They are most active on warm, rainy nights. Larvae are usually found in swift, cold mountain streams, but may occasionally be found in lakes or ponds (Reichel and Flath 1995).
Ecological Systems Associated with this Species
- Details on Creation and Suggested Uses and Limitations
How Associations Were Made
We associated the use and habitat quality (high, medium, or low) of each of the 82 ecological systems mapped in Montana for
vertebrate animal species that regularly breed, overwinter, or migrate through the state by:
- Using personal observations and reviewing literature that summarize the breeding, overwintering, or migratory habitat requirements of each species (Dobkin 1992, Hart et al. 1998, Hutto and Young 1999, Maxell 2000, Foresman 2001, Adams 2003, and Werner et al. 2004);
- Evaluating structural characteristics and distribution of each ecological system relative to the species’ range and habitat requirements;
- Examining the observation records for each species in the state-wide point database associated with each ecological system;
- Calculating the percentage of observations associated with each ecological system relative to the percent of Montana covered by each ecological system to get a measure of “observations versus availability of habitat”.
Species that breed in Montana were only evaluated for breeding habitat use, species that only overwinter in Montana were only evaluated for overwintering habitat use, and species that only migrate through Montana were only evaluated for migratory habitat use.
In general, species were associated as using an ecological system if structural characteristics of used habitat documented in the literature were present in the ecological system or large numbers of point observations were associated with the ecological system.
However, species were not associated with an ecological system if there was no support in the literature for use of structural characteristics in an ecological system, even if
point observations were associated with that system.
High, medium, and low habitat quality was assigned based on the degree to which the structural characteristics of an ecological system matched the preferred structural habitat characteristics for each species in the literature.
The percentage of observations associated with each ecological system relative to the percent of Montana covered by each ecological system was also used to guide assignments of habitat quality.
If you have any questions or comments on species associations with ecological systems, please contact Bryce Maxell at email@example.com
or (406) 444-3655.
Suggested Uses and Limitations
Species associations with ecological systems should be used to generate potential lists of species that may occupy broader landscapes for the purposes of landscape-level planning.
These potential lists of species should not be used in place of documented occurrences of species (this information can be requested at: http://mtnhp.org/requests/default.asp
) or systematic surveys for species and evaluations of habitat at a local site level by trained biologists.
Users of this information should be aware that the land cover data used to generate species associations is based on imagery from the late 1990s and early 2000s and was only intended to be used at broader landscape scales.
Land cover mapping accuracy is particularly problematic when the systems occur as small patches or where the land cover types have been altered over the past decade.
Thus, particular caution should be used when using the associations in assessments of smaller areas (e.g., evaluations of public land survey sections).
Finally, although a species may be associated with a particular ecological system within its known geographic range, portions of that ecological system may occur outside of the species’ known geographic range.
- Adams, R.A. 2003. Bats of the Rocky Mountain West; natural history, ecology, and conservation. Boulder, CO: University Press of Colorado. 289 p.
- Dobkin, D. S. 1992. Neotropical migrant land birds in the Northern Rockies and Great Plains. USDA Forest Service, Northern Region. Publication No. R1-93-34. Missoula, MT.
- Foresman, K.R. 2001. The wild mammals of Montana. Special Publication No. 12. Lawrence, KS: The American Society of Mammalogists. 278 p.
- Hart, M.M., W.A. Williams, P.C. Thornton, K.P. McLaughlin, C.M. Tobalske, B.A. Maxell, D.P. Hendricks, C.R. Peterson, and R.L. Redmond. 1998. Montana atlas of terrestrial vertebrates. Montana Cooperative Wildlife Research Unit, University of Montana, Missoula, MT. 1302 p.
- Hutto, R.L. and J.S. Young. 1999. Habitat relationships of landbirds in the Northern Region, USDA Forest Service, Rocky Mountain Research Station RMRS-GTR-32. 72 p.
- Maxell, B.A. 2000. Management of Montana’s amphibians: a review of factors that may present a risk to population viability and accounts on the identification, distribution, taxonomy, habitat use, natural history, and the status and conservation of individual species. Report to U.S. Forest Service Region 1. Missoula, MT: Wildlife Biology Program, University of Montana. 161 p.
- Werner, J.K., B.A. Maxell, P. Hendricks, and D. Flath. 2004. Amphibians and reptiles of Montana. Missoula, MT: Mountain Press Publishing Company. 262 p.
- Commonly Associated with these Ecological Systems
Forest and Woodland Systems
Wetland and Riparian Systems
- Occasionally Associated with these Ecological Systems
Shrubland, Steppe and Savanna Systems
Wetland and Riparian Systems
Larval diet is influenced by size, consisting of 52% Trichoptera larvae, 46% Plecoptera nymphs, 30% Coleoptera larvae, 28% Ephemeroptera nymphs/Coleoptera adults. Ascaphus larvae (14%) may be important food for larger larvae (Metter 1963). Females do not feed during 7 months spent in nest with eggs (Nussbaum et al. 1983).
Neoteny uncommon in small streams, but neotenes may constitute major breeding force of populations in large streams and ponds/lakes (Nussbaum and Clothier 1973).
Ovipost occurs in spring (May in coastal regions) and fall (noted in Idaho); incubation last 275 days (Nussbaum 1969). Larvae hatch at snout-vent length (SVL) 18.25 mm, but do not feed for 3 to 4 more months until they are 24.43 SVL. Metamorphose occurs during the second year (Nussbaum and Clothier 1973). Females do not feed during the 7 months spent in nest with eggs; therefore, they likely only breed during alternate years (Nussbaum et al. 1983).
Potential threats for the species across its global range probably apply also to Montana populations. Population declines or extinctions have not yet been documented, in part because the species was documented in Montana only once prior to 2005. All records are from headwaters streams and lake outlets in Mineral County. Range likely reduced during the last century from logging of mature and old-growth forest types, wildland fire, road building, and placer mining. Routine monitoring of known populations should be conducted to identify threats to each, as well as to determine their continued viability. Additonal stream surveys are desirable to determine connectivity with adjacent Idaho populations, especially between Thompson Falls and Lolo Pass (Maxell et al. 2009).
- Literature Cited AboveLegend: View WorldCat Record View Online Publication
- Maxell, B. A., P. Hendricks, M.T. Gates, and S. Lenard. 2009. Montana amphibian and reptile status assessment, literature review, and conservation plan, June 2009. Montana Natural Heritage Program. Helena, MT. 643 p.
- Metter, D.E. 1963. Stomach contents of Idaho larval Dicamptodon. Copeia (2): 435-436.
- Nussbaum, R .A. and G. W. Clothier. 1973. Population structure, growth, and size of larval Dicamptodon ensatus (Eschscholtz). Northwest Science 47(4): 218-227.
- Nussbaum, R.A. 1969. Nests and eggs of the Pacific giant salamander Dicamptodon ensatus (Eschscholtz). Herpetologica 25: 257-262.
- Nussbaum, R.A., E.D. Brodie, Jr. and R.M. Storm. 1983. Amphibians and reptiles of the Pacific Northwest. University of Idaho Press. Moscow, ID. 332 pp.
- Reichel, J. and D. Flath. 1995. Identification of Montana's amphibians and reptiles. Montana Outdoors 26(3):15-34.
- Additional ReferencesLegend: View WorldCat Record View Online Publication
Do you know of a citation we're missing?
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- Dethlefson, E.S. 1948. A subterranean nest of the Pacific giant salamander, Dicamptodon ensatus (Eschscholtz). Wasmann Collector 7: 81-84.
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- Franz, R. 1971. Notes on the distribution and ecology of the herpetofauna of northwestern Montana. Bulletin of the Maryland Herpetological Society 7: 1-10.
- Good, D.A. 1989. Hybridization and cryptic species in Dicamptodon Caudata Dicamptodontidae. Evolution 43(4): 728-744.
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- Kessel, E.L. and B.B. Kessel. 1944. Metamorphosis of the Pacific giant salamander, Dicamptodon ensatus (Eschscholtz). Wasmann Collector 6: 38-48.
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- Maxell, B. A., J. K. Werner, P. Hendricks and D. L. Flath. 2003. Herpetology in Montana: a history, status summary, checklists, dichotomous keys, accounts for native, potentially native, and exotic species, and indexed bibliography. Society for Northwestern Vertebrate Biology, Northwest Fauna Number 5. Olympia, WA. 135 p.
- Maxell, B.A. 2009. State-wide assessment of status, predicted distribution, and landscapelevel habitat suitability of amphibians and reptiles in Montana. Ph.D. Dissertation. Missoula, MT: Wildlife Biology Program, University of Montana. 294 p.
- Nussbaum, R.A. 1972. Systematics of the salamander genus Dicamptodon Strauch (Amphibia: Caudata: Ambystomatidae). Ph.D. Dissertation. Oregon State University, Corvallis, OR. 226 p.
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