Idaho Giant Salamander - Dicamptodon aterrimus
State Rank Reason (see State Rank above)
Found only within a small area in western Montana along the Idaho border, little information exists to assess threats. The intrinsic vulnerability and specific habitat requirements of this species in combination with a small known range make declines or extirpation within the state a concern.
- Details on Status Ranking and Review
Area of Occupancy
ScoreC - 4-20 km squared (about 1,000-5,000 acres)
Comment9 square km. 18,000 km of stream within range polygon by 5m in width. Assuming 2.5 m in width would still rank as a C
ScoreU - Unknown. Long-term trend in population, range, area occupied, or number or condition of occurrences unknown
ScoreU - Unknown. Short-term trend in population, range, area occupied, and number and condition of occurrences unknown.
CommentLoss of old growth habitat presents a threat as does altered stream flows due to climate change
SeverityModerate - Major reduction of species population or long-term degradation or reduction of habitat in Montana, requiring 50-100 years for recovery.
CommentAs this species occupies headwater streams, dispersal from extant populations would be difficult
ScopeHigh - > 60% of total population or area affected
CommentGiven the small area in which this species has been documented a large disturbance event could affect > 60% of all individuals
ImmediacyLow - Threat is likely to be operational within 5-20 years.
CommentFire or altered hydrology could impact this populaiton in the next 20 years
ScoreB - Moderately Vulnerable. Species exhibits moderate age of maturity, frequency of reproduction, and/or fecundity such that populations generally tend to recover from decreases in abundance over a period of several years (on the order of 5-20 years or 2-5 generations); or species has moderate dispersal capability such that extirpated populations generally become reestablished through natural recolonization (unaided by humans).
CommentModerate age of maturity and relativly high fecundity but presumably low survival
ScoreA - Very Narrow. Specialist. Specific habitat(s), substrate(s), food type(s), hosts, breeding/nonbreeding microhabitats, or other abiotic and/or biotic factor(s) are used or required by the Element in the area of interest, with these habitat(s) and/or other requirements furthermore being scarce within the generalized range of the species within the area of interest, and, the population (or the number of breeding attempts) expected to decline significantly if any of these key requirements become unavailable.
CommentSpecies is found only in cold mountain streams in a small region of Idaho and Montana
Raw Conservation Status Score
3.5 + -0.5 (geographic distribution) + -0.5 (environmental specificity) + 0 ( trend) + -0.25 (intrinsic vulnerability) = 2.25
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
Observations in Montana Natural Heritage Program Database
Number of Observations:
(Click on the following maps and charts to see full sized version)
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 (common or occasional) 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 2012, 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 observation 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 listed as associated with 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 listed as 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.
Common versus occasional association with an ecological system was assigned based on the degree to which the structural characteristics of an ecological system matched the preferred structural habitat characteristics for each species as represented in scientific 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 assignment of common versus occasional association.
If you have any questions or comments on species associations with ecological systems, please contact the Montana Natural Heritage Program's Senior Zoologist.
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. 2012. Mammals of Montana. Second edition. Mountain Press Publishing, Missoula, Montana. 429 pp.
- 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
- Occasionally Associated with these Ecological Systems
Forest and Woodland Systems
Recently Disturbed or Modified
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.The species is more likely to occur in road-less areas (Sepulveda and Lowe 2009), so changes in land use over the last century have undoubtedly impacted this species. 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 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.
- Sepulveda, A.J. and W.H. 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.
- Additional ReferencesLegend: View Online Publication
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- Anderson, J.D. 1969. Dicamptodon and D. ensatus. Catalogue of American Amphibians and Reptiles. Pp. 76.1-76.2.
- Antonelli, A.L., R.A. Nussbaum and S.D. Smith. 1972. Comparative food habits of four species of stream-dwelling vertebrates (Dicamptodon ensatus, D. copei, Cottus tenius, Salmo gairdnei) Northwest Science 46: 277-289.
- Blaustein, A.R., J.J. Beatty, H. Deanna, and R.M. Storm. 1995. The biology of amphibians and reptiles in old-growth forests in the Pacific Northwest. General Technical Report PNW-GTR-337. Portland, OR: U.S. Department of Agriculture, Forest Service, Pacific Northwest Research Station. 98 p.
- Boundy, J. 2001. Herpetofaunal surveys in the Clark Fork Valley region, Montana. Herpetological Natural History 8: 15-26.
- Brunson, R.B. 1955. Check list of the amphibians and reptiles of Montana. Proceedings of the Montana Academy of Sciences 15: 27-29.
- Bury, R.B. 1972. Small mammals and other prey in the diet of the Pacific Giant salamander (Dicamptodon ensatus). American Midland Naturalist 87(2): 524-526.
- Carlson, J. (Coordinator, Montana Animal Species of Concern Committee). 2003. Montana Animal Species of Concern. Helena, MT: Montana Natural Heritage Program and Montana Fish, Wildlife, and Parks. In Press. 12p.
- Cassirer, E.F. 1995. Wildlife inventory, Craig Mountain, Idaho. Idaho Department of Fish and Game, Lewiston Idaho. 182 pp.
- Cochran, D.C. 1961. Type specimens of reptiles and amphibians in the United States National Museum. U.S. National Museum Bulletin (220) xv + 291pp.
- Connor, E.J., W.J. Trush, and A.W. Knight. 1988. Effects of logging on Pacific giant salamanders: influence of age-class composition and habitat complexity. Bulletin of the Ecological Society of America 69 (Suppl.): 104-105.
- Cope, E.D. 1867. A review of the species of the Amblystomidae. Proceedings of the Academy of Natural Sciences of Philadelphia 19: 166-211.
- Cope, E.D. 1867. Proceedings of the Academy of National Sciences, Philadelphia, Volume 19, 2nd Series, p. 201.
- Cope, E.D. 1875. Check-list of North American Batrachia and Reptilia; with a systematic list of the higher groups, and an essay on geographical distribution. Based on the specimens contained in the U.S. National Museum. U.S. Natioanl Museum Bulletin 1: 1-104.
- Coues, E. and H. Yarrow. 1878. Notes on the herpetology of Dakota and Montana. Bulletin of the U.S. Geological Geographic Survey of the Territories 4: 259-291.
- Crother, B.I. (ed.) 2008. Scientific and standard English names of amphibians and reptiles of North America north of Mexico. SSAR Herpetological Circular No. 37:1-84.
- Daugherty, C.H. and F.W. Allendorf. 1977b. The taxonomic value of genetic distance: data from two amphibians. Abstract. American Zoologist 17(4): 973.
- Daugherty, C.H., F.W. Allendorf, W.W. Dunlap and K.L. Knudsen. 1983. Systematic implications of geographic patterns of genetic variation in the genus Dicamptodon. Copeia 1983: 679-691.
- Dethlefson, E.S. 1948. A subterranean nest of the Pacific giant salamander, Dicamptodon ensatus (Eschscholtz). Wasmann Collector 7: 81-84.
- Flath, D.L. 1998. Species of special interest or concern. Montana Department of Fish, Widlife and Parks, Helena, MT. March, 1998. 7 p.
- Flath, D.L. 1979. Nongame species of special interest or concern: Mammals, birds, reptiles, amphibians, fishes. Wildlife Division, Montana Department of Fish and Game. Helena, MT.
- Franz, R. 1970a. Additional notes on the feeding of larval giant salamanders, Dicamptodon ensatus. Bulletin of the Maryland Herpetological Society 6(3): 51-52.
- 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.
- Hendricks, P. and J.D. Reichel. 1996. Amphibian and reptile survey of the Bitterroot National Forest: 1995. Montana Natural Heritage Program. Helena, MT. 95 p.
- Kelsey, K.A. 1994. Responses of headwater stream amphibians to forest practices in western Washington. Northwest Science 68(2): 133.
- Kessel, E.L. and B.B. Kessel. 1943a. The rate of growth of older larvae of the Pacific giant salamander, Dicamptodon ensatus (Eschscholtz). Wasmann Collector 5: 141-142.
- Kessel, E.L. and B.B. Kessel. 1943b. The rate of growth of the young larvae of the Pacific Giant Salamander, Dicamptodon ensatus (Eschscholtz). Wasmann Collector 5: 108-111.
- Kessel, E.L. and B.B. Kessel. 1944. Metamorphosis of the Pacific giant salamander, Dicamptodon ensatus (Eschscholtz). Wasmann Collector 6: 38-48.
- L. L. C. Jones, W. P. Leonard and D. H. Olson, eds. 2005. Amphibians of the Pacific Northwest. Seattle Audubon Society: Seattle, WA, 227 pp.
- Lind, A.J. and H.H. Welsh, Jr. 1990. Predation by Thamnophis couchii on Dicamptodon ensatus. Journal of Herpetology 24(1): 104-106.
- Maughan, O.E., M.G. Wickham, P. Laumeyer and R.L. Wallace. 1976. Records of the Pacific Giant Salamander, Dicamptodon ensatus, (Amphibia, Urodela, Ambystomatidae) from the Rocky Mountains in Idaho. Journal of Herpetology 10(3): 249-251.
- 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.
- 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.
- Nussbaum, R.A. 1972. Systematics of the salamander genus Dicamptodon Strauch (Amphibia: Caudata: Ambystomatidae). Ph.D. Dissertation. Oregon State University, Corvallis, OR. 226 p.
- Nussbaum, R.A. 1976. Geographic variation and systematics of the salamanders of the genus Dicamptodon Strauch (Ambystomatidae). Museum of Zoology, University of Michigan Miscellaneous Publication Number 149. 94 pp.
- Reed, C.A. 1949. The problem of metamorphosis in the western marbled salamander Dicamptodon ensatus. Copeia 1949: 81.
- Savage, J.M. 1952. The distribution of the Pacific giant salamander, Dicamptodon ensatus, east of the Cascade Mountains. Copeia 1952: 183.
- Stebbins, R. C. 2003. A field guide to western reptiles and amphibians. 3rd Edition. Houghton Mifflin Company, Boston and New York. 533 p.
- Thompson, L.S. 1982. Distribution of Montana amphibians, reptiles, and mammals. Bozeman: Montana Audubon Council. 24 pp.
- Welsh, H.H., Jr. 1986a. Dicamptodon ensatus (Pacific Giant Salamander). Behavior. Herpetological Review 17(1): 19.
- Welsh, H.H., Jr. 1986b. Life history notes. Caudata. Dicamptodon ensatus (Pacific giant salamander). Herpetological Review 17(1): 19.
- Werner, J.K., B.A. Maxell, P. Hendricks and D.L. Flath. 2004. Amphibians and Reptiles of Montana. Mountain Press Publishing Company: Missoula, MT. 262 pp.
- Yarrow, H.C. 1882. Check list of North American reptilia and batrachia, with catalogue of specimens in the U.S. National Museum. United States National Museum Bulletin 24. 249 p.
- Additional Sources of Information Related to "Amphibians"