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Montana Field Guides

Idaho Giant Salamander - Dicamptodon aterrimus

Species of Concern
Native Species

Global Rank: G3G4
State Rank: S2
(see State Rank Reason below)

Agency Status

External Links

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
    Idaho Giant Salamander (Dicamptodon aterrimus) Conservation Status Review
    Review Date = 05/03/2018
    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

    Long-term Trend

    ScoreU - Unknown. Long-term trend in population, range, area occupied, or number or condition of occurrences unknown


    Short-term Trend

    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

    Intrinsic Vulnerability

    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

    Environmental Specificity

    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

    Score 3.5 + -0.5 (geographic distribution) + -0.5 (environmental specificity) + 0 ( trend) + -0.25 (intrinsic vulnerability) = 2.25

General Description
Eggs are laid singly, but placed together in a mass approximately 15 cm (5.9 in) wide by 20 cm (7.9 in) long containing 129 to 200 eggs (Nussbaum et al. 1983; Jones et al. 1990). Each ovum is pure white and is surrounded by six clear jelly layers (Nussbaum et al. 1983). Ovum diameters are approximately 6.5 mm (0.26 in) (Nussbaum et al. 1983). The eggs are oblong and attached on a short pedicle to the substrate in flowing water. Total egg widths are 16-21 mm (0.6-0.8 in) and total egg heights are 22-33 mm (0.9-1.3 in), including the jelly layers (Jones et al. 1990).

Short external feathery gills are present at the base of the head. Body color varies to match the local substrate, but they usually have a dark dorsal color with lighter stripes behind the eyes (Nussbaum et al. 1983). The dorsal tail fin is mottled and begins at or behind the rear limbs. Hatchlings have a total length (TL) of 34 to 40 mm (1.3-1.6 in) and reproductively mature larvae (neotenic) larvae may reach a TL of 351 mm (13.8 in) (Nussbaum et al. 1983; Jones et al. 1990).

Dorsal color is dark brown or almost black in base color and light tan or coppery marbling is usually present and is often brightest on the head (Nussbaum et al. 1983). They are heavy-bodied, with a large head and muscular legs. The size of new metamorphs is highly variable but adults may reach a TL of up to 340 mm (13.4 in) (Nussbaum et al. 1983).

Diagnostic Characteristics
No other salamander would be found as an aquatic inhabitant of streams in Montana. Adult Idaho Giant Salamanders are 3-4 times larger than that of adults of Long-toed (Ambystoma macrodactylum) and Western Tiger Salamanders (A. mavortium). Other larval salamanders found in Montana live in ponds, have long, feathery gills, and a dorsal fin originating far forward of the rear legs.

Species Range
Montana Range Range Descriptions


Western Hemisphere Range


Range Comments
In 2005, Idaho Giant Salamander were confirmed to be present in Mineral County south of Haugan by Jennifer Copenhaver of the Lolo National Forest. Electrofishing surveys in the same region in 2006 and 2007 detected more than 100 individuals in 51 different portions of 11 different tributaries of 3 major watersheds. Prior to these observations, the species had been reported or illustrated as occurring in Mineral and Ravalli counties by several authors (Anderson 1969; Black 1970a; Daugherty et al. 1983; Stebbins 2003; Good 1989; Reichel and Flath 1995; Petranka 1998). However, as noted by Nussbaum (1976) and Savage (1952) all these distributional claims were apparently based on the assumption that the holotype specimen (USNM 5242) described by Cope (1867) and later by Cope (1889) as being collected by Lieutenant Mullan from the “North Rocky Mountains” was actually collected in western Montana. Thus, prior to the detection in 2005 there was no valid documentation of their presence in the state (Franz 1971; Nussbaum 1976; Maxell et al. 2003; Werner et al. 2004).

Maximum elevation: 1,737 m (5,700 ft) in Mineral County (Eric Dallalio and Phil Jellen, personal communication; MTNHP 2007).

Observations in Montana Natural Heritage Program Database
Number of Observations: 72

(Click on the following maps and charts to see full sized version) Map Help and Descriptions
Relative Density



(Observations spanning multiple months or years are excluded from time charts)


Larvae and aquatic adults are the most likely life history stage to be observed as they may reach high densities in the pools of swift, cold mountain streams and may also be found in lakes or ponds (Nussbaum et al. 1983; Reichel and Flath 1995). Terrestrial adults are seldom seen and can be found in moist coniferous forests under rocks, bark and logs and aquatically under stones in mountain streams or lakes up to 2,165 m (7,100 ft). Adults are active terrestrially on warm, rainy nights (Nussbaum et al. 1983).

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:
    1. 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);
    2. Evaluating structural characteristics and distribution of each ecological system relative to the species' range and habitat requirements;
    3. Examining the observation records for each species in the state-wide point observation database associated with each ecological system;
    4. 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: 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.

    Literature Cited
    • 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.

Food Habits
Adults may feed on a variety of invertebrates and small vertebrates. Females do not feed for the seven months spent in nest with eggs. Larvae feed on fish and invertebrates, but diet is influenced by their size. It can consist of Trichoptera larvae, Plecoptera nymphs, Coleoptera larvae, Ephemeroptera nymphs/Coleoptera adults. Additionally, Ascaphus larvae may be important food for larger larvae (Metter 1963; Nussbaum et al. 1983).

Larvae usually metamorphose in 18-24 months but may become sexually mature (paedogenesis) and reproduce as larvae (Nussbaum et al. 1983; Parker 1993). Neoteny is uncommon in small streams, but neotenes may constitute major breeding force of populations in large streams and ponds/lakes (Nussbaum and Clothier 1973).

Reproductive Characteristics
Adults breed in the spring or fall in hidden water-filled nest chambers beneath logs and stones or in crevices in mountain streams or lakes. Ovipostioning occurs in spring (May in coastal regions) and fall (noted in Idaho) with incubation lasting for 275 days. Females guard the eggs throughout the incubation period; therefore, they likely only breed during alternate years (Nussbaum 1969; Nussbaum et al. 1983). Larvae hatch at snout-vent length (SVL) 18.25 mm (0.72 in), but do not feed for 3 to 4 more months until they are 24.43 mm (0.96 in) SVL. Metamorphose occurs during the second year (Nussbaum and Clothier 1973).

The following was taken from the Status and Conservation section for the Idaho Giant Salamander account in Maxell et al. 2009

Potential threats for the species across its global range probably apply also to Montana populations. Because Idaho Giant Salamanders were only recently confirmed in Montana, the extent of their distribution and conservation status are still largely uncertain. However, because their distribution appears to be limited to a handful of headwater streams adjacent to the Idaho border, they face a variety of risks associated with limited distribution. The range of the Idaho Giant Salamander in Montana has likely been reduced during the last century through habitat fragmentation from logging of mature and old-growth forest types, wildland fire and fire management activities, road building, placer mining and the use of piscicides. 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. Individual studies that specifically identify risk factors or other issues relevant to the conservation of Idaho Giant Salamanders have not been reviewed at this time. Routine monitoring of known populations should be conducted to identify threats to each, as well as to determine their continued viability. Additional 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
    • Anderson, J.D. 1969. Dicamptodon and D. ensatus. Catalogue of American Amphibians and Reptiles. Pp. 76.1-76.2.
    • Black, J.H. 1970a. Amphibians of Montana. Montana Wildlife, Montana Fish and Game Commission. Animals of Montana Series 1970(1): 1-32.
    • 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. 1889. The Batrachia of North America. Bulletin of the U.S. National Museum 34: 1-525, figs. 1-119, pls. 1-86.
    • 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.
    • 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.
    • Jones, L.L.C., R.B. Bury and P.S. Corn. 1990. Field observation of the development of a clutch of pacific giant salamander (Dicamptodon tenebrosus) eggs. Northwestern Naturalist 71: 93-94.
    • 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., 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. 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.
    • 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.
    • Petranka, J.W. 1998. Salamanders of the United States and Canada. Smithsonian Institution Press, Washington D.C. 587 pp.
    • Reichel, J. and D. Flath. 1995. Identification of Montana's amphibians and reptiles. Montana Outdoors 26(3):15-34.
    • Savage, J.M. 1952. The distribution of the Pacific giant salamander, Dicamptodon ensatus, east of the Cascade Mountains. Copeia 1952: 183.
    • 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.
    • Stebbins, R. C. 2003. A field guide to western reptiles and amphibians. 3rd Edition. Houghton Mifflin Company, Boston and New York. 533 p.
    • 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.
  • Additional ReferencesLegend:   View Online Publication
    Do you know of a citation we're missing?
    • 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 January 2003. 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. 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.
    • Dethlefson, E.S. 1948. A subterranean nest of the Pacific giant salamander, Dicamptodon ensatus (Eschscholtz). Wasmann Collector 7: 81-84.
    • 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.
    • Flath, D.L. 1998. Species of special interest or concern. Montana Department of Fish, Widlife and Parks, Helena, MT. March, 1998. 7 p.
    • Franz, R. 1970a. Additional notes on the feeding of larval giant salamanders, Dicamptodon ensatus. Bulletin of the Maryland Herpetological Society 6(3): 51-52.
    • Hendricks, P. and J.D. Reichel. 1996a. Amphibian and reptile survey of the Bitterroot National Forest: 1995. Montana Natural Heritage Program. Helena, MT. 95 p.
    • Honeycutt, R.K., W.H. Lowe, and B.R. Hossack. 2016. Movement and survival of an amphibian in relation to sediment and culvert design. The Journal of Wildlife Management 80(4):761-770.
    • Jones, Lawrence L. C., W. P. Leonard and D. H. Olson, eds. 2005. Amphibians of the Pacific Northwest. Seattle Audubon Society: Seattle, WA, 227 pp.
    • Joslin, Gayle, and Heidi B. Youmans. 1999. Effects of recreation on Rocky Mountain wildlife: a review for Montana. [Montana]: Montana Chapter of the Wildlife Society.
    • 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.
    • 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.
    • Nussbaum, R.A. 1972. Systematics of the salamander genus Dicamptodon Strauch (Amphibia: Caudata: Ambystomatidae). Ph.D. Dissertation. Oregon State University, Corvallis, OR. 226 p.
    • Reed, C.A. 1949. The problem of metamorphosis in the western marbled salamander Dicamptodon ensatus. Copeia 1949: 81.
    • 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.
    • 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.
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