AmphibiaWeb - Ambystoma macrodactylum


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Ambystoma macrodactylum Baird, 1850
Long-toed Salamander, Eastern Long-Toed Salamander, Santa Cruz Long-Toed Salamander, Northern Long-Toed Salamander, Western Long-Toed Salamander, Southern Long-Toed Salamander
Subgenus: Xiphonura
family: Ambystomatidae
genus: Ambystoma
Species Description: Baird, S. F. (1850 "1849"). Revision of the North American tailed-batrachia, with descriptions of new genera and species [Including: Descriptions of four new species of North American salamanders, and one new species of scink, pp. 292–294]. Journal of the Academy of Natural Sciences of Philadelphia. Series 2(1), 281–294.

© 2011 Richard Sage (1 of 140)
Conservation Status (definitions)
IUCN Red List Status Account Least Concern (LC)
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National Status None
Regional Status The subspecies, Ambystoma macrodactylum croceum, is both State listed endangered and Federally listed endangered
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bookcover The following account is modified from Amphibian Declines: The Conservation Status of United States Species, edited by Michael Lannoo (©2005 by the Regents of the University of California), used with permission of University of California Press. The book is available from UC Press.

Ambystoma macrodactylum Baird, 1849
Long-Toed Salamander

David S. Pilliod
Julie A. Fronzuto

1. Historical versus Current Distribution. Historical and current distributions of long-toed salamanders (Ambystoma macrodactylum) are similar; there is no evidence of a change in distribution. The type-locality for this common, broadly distributed northwestern species is Astoria, Oregon (Baird, 1849), with the syntype deposited at the U.S. National Museum 4042 (Ferguson, 1963). Populations occur from the Alaskan Peninsula across British Columbia; south through Washington into Oregon and the Sierra Nevada of California; and across the Rocky Mountains into eastern Alberta, western Montana, and central Idaho. Isolated populations occur in central California (Russell and Anderson, 1956) and in southeastern Oregon (Petranka, 1998). An erroneous record exists from Iowa (Ruthven, 1912). There are five subspecies recognized, based primarily on morphologically distinguishable dorsal banding patterns (Mittleman, 1948; Ferguson, 1961a; Crother et al., 2000). Generally, each subspecies is distributed allotopically along north–south ranges (see Petranka, 1998) as follows:
· Western long-toed salamanders (A. m. macrodactylum; Baird, 1849) range from Vancouver Island and southwestern British Columbia through western Washington (west of the Cascade Mountains) and north of the Calapooya Divide in western Oregon (Nussbaum et al., 1983).
· Eastern (also cited as central or Columbia) long-toed salamanders (A. m. columbianum; Ferguson, 1961a) range from southeastern Alaska through British Columbia, eastern Washington, Oregon (east of the Willamette Valley), and into central Idaho (Nussbaum et al., 1983; Petranka, 1998).
· Northern (also erroneously cited as eastern or western) long-toed salamanders (A. m. krausei, Peters, 1882) range from eastern British Columbia and Idaho through western Alberta and Montana (Nussbaum et al., 1983; Petranka, 1998; Walsh, 1998; Graham and Powell, 1999).
· Southern long-toed salamanders (A. m. sigillatum; Ferguson, 1961a) range from southwestern Oregon (south of Calapooya Divide) into the Sierra Nevada as far south as Carson Pass in California (R. Cutter, personal observations).
· Santa Cruz long-toed salamanders (A. m. croceum; Russell and Anderson, 1956) represent an isolated subspecies found at 11 locations in Santa Cruz and Monterey counties, California (U.S.F.W.S., 1999c). Listed in 1967, this is the only Federally Endangered subspecies of A. macrodactylum (Bury et al., 1980). Recent efforts to halt habitat threats to this narrowly distributed population are being evaluated (Ruth, 1988; U.S.F.W.S., 1999c).
2. Historical versus Current Abundance. Little information exists regarding the historical abundance of long-toed salamanders; it is therefore difficult to determine if abundance has changed over time. In addition, determining the abundance of adults in an area is usually difficult. Even when populations are large, long-toed salamanders are rarely found outside of the breeding season. When encountered in ponds during spring breeding aggregations, long-toed salamanders have been considered locally abundant (Anderson, 1967a; Beneski et al., 1986; Powell et al., 1997; Fukumoto and Herrero, 1998). Historical descriptions from Crater Lake, Oregon (Evermann, 1897; Bishop, 1943), Corvallis, Oregon (Storm and Pimentel, 1954), and Mt. Rainier, Washington (Slater, 1936b; Stebbins, 1966), indicate long-toed salamanders were abundant in those areas. In northwestern Idaho, over 2,030 adults were captured by a drift fence encompassing a small (0.3 ha), fishless pond, providing habitat for an estimated 3,141 breeding adults (Beneski et al., 1986). Recent mark-recapture studies in Alberta found similarly large population sizes (Powell et al., 1997; Fukumoto and Herrero, 1998). However, the effective population sizes (estimated from allozyme data) of six high elevation populations in Idaho and Montana were considerably smaller (mean = 123; Funk et al., 1999). A five-year census of 11 high elevation basins in central Idaho indicated that long-toed salamanders may have been extirpated or reduced to low numbers in six of these basins, possibly due to the stocking of non-native trout into deep, fishless breeding habitats (Pilliod and Peterson, 2001).
3. Life History Features.
A. Breeding. Reproduction is aquatic.
i. Breeding migrations. In the Pacific Northwest, long-toed salamanders are the earliest breeding amphibians (Leonard et al., 1993; Corkran and Thoms, 1996), often migrating across snow and depositing eggs before complete ice-out. In the Willamette Valley, Oregon, adults migrate to breeding ponds in late October to early November (Stebbins, 1966; Nussbaum et al., 1983; Leonard et al., 1993), and as late as June–July at higher elevations in the Cascades, Rockies, Sierra Nevada, and Wallowas (Kezer and Farner, 1955; Stebbins, 1966; Howard and Wallace, 1985; Leonard et al., 1993; Walls et al., 1993a; Pilliod, 2001; Thompson, 2001). Males are the first to arrive at breeding ponds (Nussbaum et al., 1983; Beneski et al., 1986), probably to court arriving females (Slater, 1936a; Knudsen, 1960; Anderson, 1961) and compete with other males (Verrell and Pelton, 1996). While females, as a group, spend approximately 3 wk at a breeding site (Beneski et al., 1986), depositing eggs over a 6–7 d period (Anderson, 1967a), individual females spend only 1–2 d (Verrell and Pelton, 1996). Males generally leave the breeding site ~ 1 wk after the females (Beneski et al., 1986), but may remain in the ponds for the entire breeding season (up to 2 mo or more; Anderson, 1968; Beneski et al., 1986). In ephemeral habitats, breeding may only last 1–2 d (Walls et al., 1993a).
ii. Breeding habitat. Long-toed salamanders are opportunistic breeders, depositing eggs in a variety of habitats, including seeps (Hamilton et al., 1998); along the backwaters of slow-flowing streams (Beneski et al., 1986; Hamilton et al., 1998; Llewelyn and Peterson, 1998), temporary pools at lower elevations (Leonard and Klaus, 1994); and small–large permanent lakes and ponds at higher elevations (Anderson, 1967a; Howard and Wallace, 1985; Leonard et al., 1993; Hamilton et al., 1998; Pilliod, 2001) and higher latitudes (Green and Campbell, 1984). Eggs and larvae have also been found in disturbed areas, such as newly formed (Hamilton et al., 1998), recently disturbed (Corkran and Thoms, 1996), and human-influenced (Beneski et al., 1986; Llewelyn and Peterson, 1998; Monello and Wright, 1999) pools down to the size of tire ruts (K.R. McAllister, personal communication).
B. Eggs.
i. Egg deposition sites. Eggs are deposited in shallow water (< 0.5 m) with silt-mud substrates, but also along rocky shorelines (Hamilton et al., 1998). Eggs are attached to vegetation, floating or submerged woody debris (logs, branches), and rocks, or placed unattached on the bottom in shallow (< 20 cm) water (Slater, 1936a,b; Stebbins, 1954a; Nussbaum et al., 1983; Howard and Wallace, 1985; Corkran and Thoms, 1996).
ii. Clutch size. Clutch size is geographically variable, from 90–411 eggs (Slater, 1936b; Gordon, 1939; Ferguson, 1961a; Anderson, 1967a; Howard and Wallace, 1985; see also Petranka, 1998). Females deposit eggs over several hr, releasing 1–81 eggs in a cluster before moving to a new location in the pond (Petranka, 1998; Maxell, 2000).
C. Larvae/Metamorphosis.
i. Length of larval stage. Length of larval period varies with elevation, latitude, and pool permanence (Slater, 1936b; Kezer and Farner, 1955; Anderson, 1967a; Howard and Wallace, 1985; Watson, 1997). Eggs hatch in 5–35 d, depending on water temperature (Anderson, 1967a; Leonard et al., 1993). The larval period can be as short as 50 d in some temporary ponds (Nussbaum et al., 1983) or last ≤ 3 yr in permanent lakes at higher elevations (Bishop, 1943; Stebbins, 1966; Leonard et al., 1993; Pilliod, 2001).
ii. Larval requirements.
a. Food. Larvae are opportunistic carnivores and begin feeding shortly after hatching (Petranka, 1998). Prey size generally increases with salamander body size and includes crustaceans (amphipods, cladocerans, copepods), a variety of aquatic and terrestrial insects (coleopterans, dipterans, ephemeropterans, plecopterans, tricopterans), mollusks (gastropodans, pelecypodans), annelids (hirudineans, oligochaetes), and ranid frog tadpoles (Anderson, 1968; Tyler et al., 1998a). Larger larvae may cannibalize smaller larvae (Anderson, 1967a; Walls et al., 1993a), possibly resulting in increased growth and size at metamorphosis of the cannibals (Wildy et al., 1998, 1999).
b. Cover. Because of their diverse diets, feeding larvae are found in the open water column and within cover. During the day, larvae may use cover to avoid predation from vertebrate and invertebrate predators and are often found in or under bottom detritus (rotting leaves, woody debris), submerged logs, rocks, and aquatic vegetation (Anderson, 1967a; Green and Campbell, 1984; Liss et al., 1995; Corkran and Thoms, 1996; Munger et al., 1997b; Hamilton et al., 1998; Petranka, 1998). In fishless lakes, larvae may move more freely across open substrates or in the water column (Liss et al., 1995; Tyler et al., 1998a). However, in fishless ponds in southeastern Washington that contain a variety of other vertebrate and invertebrate predators, larvae are seldom observed in open water and even less often captured in minnow traps (J.A.F. and P. Verrell, unpublished data). At high elevations, second-year larvae may use more open habitat compared to first-year and metamorphosing larvae that remain under cover (Anderson, 1967a).
iii. Larval polymorphism. Morphologically distinct cannibalistic larvae have been reported from at least one small, subalpine pond in Oregon (Walls et al., 1993a,b; Petranka, 1998). These cannibalistic larvae have longer, wider heads and larger vomerine teeth compared to conspecifics of the same size and from the same population that were reared in the laboratory on a diet of live Tubifex (Walls et al., 1993a). Diet is one of several intrinsic and extrinsic factors that influence the expression of the cannibalistic larval morphology (Walls et al., 1993b).
iv. Features of metamorphosis. The timing of metamorphosis varies with environmental conditions and is triggered by either intrinsic factors (possibly size of the animal) or extrinsic factors such as temperature and pond drying (Anderson, 1967a). Size at metamorphosis is highly variable, ranging from 23–48 mm SVL (40.5–90 mm TL; Carl, 1942; Howard and Wallace, 1985). Although size at metamorphosis does not appear to be associated with elevation (Anderson, 1967a), larvae that take 2–3 yr to transform are generally larger at metamorphosis (Kezer and Farner, 1955; Howard and Wallace, 1985).
v. Post-metamorphic migrations. Long-toed salamanders exhibit a strong breeding site fidelity and generally will only migrate within 100 m of breeding ponds (Anderson, 1967a; Sheppard, 1977; Powell et al., 1997). However, outside of the breeding season, longer migrations may occur. For example, in Montana, adults have been captured in pitfall traps at least 600 m from the nearest breeding site (J. Pierson, unpublished data, as cited in Maxell, 2000). Terrestrial post-metamorphic migrations are generally associated with rains, high soil moisture, and air temperatures above 0 ˚C (Anderson, 1967a; Howard and Wallace, 1985; Beneski et al., 1986; Powell et al., 1997; Fukumoto and Herrero, 1998). When moisture levels are sufficient, metamorphic animals disperse away from breeding sites shortly after transforming (Anderson, 1967a). Dispersal of newly metamorphosed animals may be spread out over several months (May–August in southeastern Washington; J.A.F. and P. Verrell, unpublished data) or occur as a mass migration when conditions permit (Anderson, 1967a; Marnell, 1997).
vi. Neoteny. Although the prevalence of delayed metamorphosis in long-toed salamanders indicates a potential for neoteny (Sprules, 1974a), paedomorphosis—retention of larval characteristics in reproductively active adults—has not been observed.
D. Juvenile Habitat. As far as we know, juvenile habitats are similar to adults. Recently transformed juveniles may remain close to the breeding pond (under cover objects) until conditions for migration are favorable (Anderson, 1967a).
E. Adult Habitat. Adult long-toed salamanders occur in a wide range of habitats ranging from sea level to 3,000 m in California (Stebbins, 1966) to ≤ 2,030 m in Washington (Leonard et al., 1993) to 2,470 m in Oregon (Howard and Wallace, 1981, 1985) and 2,725 m in Idaho (Munger et al., 1997b; Pilliod, 2001). Suitable habitats include semiarid grasslands and sagebrush steppes, alpine meadows, dry oak woodlands, humid coniferous forests, rocky shorelines of subalpine lakes, beaver ponds (Reichel, 1996), and even disturbed agricultural areas (Nussbaum et al., 1983; Monello and Wright, 1999), timber harvest areas (Hamilton et al., 1998; Naughton et al., 2000), pastures (Leonard et al., 1993), and residential green belts (Leonard et al., 1993). Adults are typically subterranean outside of the breeding season, hiding under logs, bark, rocks, and within rotten wood or rodent burrows, generally within 100 m of water (Gordon, 1939; Bishop, 1943; Stebbins, 1954a; Stebbins, 1966; Green and Campbell, 1984; Corkran and Thoms, 1996; Powell et al., 1997). In a comprehensive search conducted in August, of all cover objects within 10 m of the shoreline of three high elevation lakes in central Idaho, the majority (82%) of adults were found under logs (5–50 cm diameter) within 5 m of water (D.S.P. and M. Reed, unpublished data). Microhabitats are typically associated with higher substrate moisture (Anderson, 1967a). When soil moisture levels are low, juveniles and adults may aggregate (≤ 43 individuals have been observed in close proximity) and entwine (Anderson, 1967a), a behavior that reduces water loss (Alvarado, 1967). Adults can be found above ground at night or during rains in the summer months not associated with the breeding season. Migrations do not necessarily occur along stream corridors or within obvious habitat types (Beneski et al., 1986).
F. Home Range Size. Due to the limited vagility of long-toed salamanders, home range sizes are relatively small. Sheppard (1977) monitored 25 salamanders with implanted radioactive tags from July–October in Alberta and estimated (minimum-area convex polygon) home ranges to be 115.6 m2 for females, 167.5 m2 for males, and 281.6 m2 for juveniles. The rugged topography in which long-toed salamanders are often found may reduce movements between distant populations, potentially reducing gene flow among populations (Howard and Wallace, 1981). However, in the Bitterroot Mountains in Montana, allozyme data indicate populations within basins are panmictic, with salamanders moving among breeding populations (Tallmon et al., 2000). These allozyme data also suggest that salamanders move across mountain ridges more frequently than they move across valley bottoms. In Idaho, a salamander was observed in June crossing a snow-covered ridge that separated two cirque basins at an elevation of 2,600 m (D.S.P., personal observations).
G. Territories. Although larvae are not known to be territorial, they are aggressive, possibly resulting in the spacing of individuals (Anderson, 1967a). Both juveniles and adults can be aggressive in competition over food (J.A.F., personal observations). Non-breeding adults may be social, rather than territorial—conspecifics aggregate rather than exclude each other Verrell and Davis (2003).
H. Aestivation/Avoiding Dessication. Aestivation has not been documented, but low precipitation may inhibit migratory behavior and result in reduced surface activity (Howard and Wallace, 1985).
I. Seasonal Migrations. Long-toed salamanders migrate to breeding habitats in the spring and to overwintering habitats in the fall. Individuals home to breeding and wintering locations, but do not appear to follow population-level migratory routes (Beneski et al., 1986).
J. Torpor (Hibernation). Although little is known about long-toed salamander hibernation, adults probably hibernate terrestrially. Sheppard (1977) found three terrestrial hibernacula aggregations located in gravel substrate at 45–70 cm below the ground surface (frost line was estimated at 45 cm). When water temperatures drop and surface ice forms, over-wintering larvae become less active and retreat under logs and bottom debris (Anderson, 1967a). In shallow (< 1 m), high elevation ponds and ephemeral pools, larvae may move into subsurface springs when pools freeze solid (D.S.P., personal observations).
In lowland areas, adults can remain active year-round (Stebbins, 1966). In southeastern Washington, adults have been observed migrating to breeding ponds during the coldest winter months and have been retrieved from submerged minnow traps in early January, below ≤ 15 cm of ice, with air temperatures from 0 to -16 ˚C (J.A.F. and P. Verrell, unpublished data).
K. Interspecific Associations/Exclusions. Long-toed salamanders occur in habitats used by other amphibians, including blotched tiger salamanders (Ambystoma tigrinum melanostictum), California slender salamanders (Batrachoseps attenuatus), arboreal salamanders (Aneides lugubris), rough-skinned newts (Taricha granulosa), Pacific treefrogs (Hyla regilla,) mountain yellow-legged frogs (Rana muscosa), Oregon spotted frogs (Rana pretiosa), and western toads (Bufo boreas). Long-toed salamanders co-occur with Columbia spotted frogs (Rana luteiventris) at > 80% of survey sites in Idaho and Montana (Werner and Reichel, 1994; O'Siggins, 1995; Munger et al., 1997b; Llewelyn and Peterson, 1998; Pilliod, 2001). This is probably due to a similarity in habitat characteristics, but adult and larval long-toed salamanders may also utilize frequently abundant Columbia spotted frog tadpoles as a food source (Munger et al., 1997b). In Washington, long-toed salamanders and northwestern salamanders (Ambystoma gracile) have generally allotopic distributions, possibly resulting from competition and predation (Hoffman et al., 2003). Introduced trout (Oncorhynchus sp.; Liss et al., 1995) and goldfish (Carassius auratus; Monello and Wright, 2001) prey on long-toed salamander eggs and larvae, substantially reducing their numbers, sometimes to the point of excluding them from breeding sites (Liss et al., 1995; Munger et al., 1997b; Beck et al., 1998; Tyler et al., 1998a; Yeo and Peterson, 1998; Funk and Dunlap, 1999; Hoffman and Pilliod, 1999; Monello and Wright, 1999; Pilliod and Peterson, 2001). Artificial-pond experiments indicate that trout reduce growth and survivorship of larvae, presumably due to both indirect and direct effects of predation, such as limited foraging activity associated with refuge use and increased predation (Tyler et al., 1998b).
L. Age/Size at Reproductive Maturity. Sexual maturity is reached in 1–3 yr (at 50–55 mm SVL) after metamorphosis for both sexes (Anderson, 1967a; Nussbaum et al., 1983; Green and Campbell, 1984; Howard and Wallace, 1985; Russell et al., 1996).
M. Longevity. Skeletochronological techniques indicate that long-toed salamanders live ≤ 10 yr (Russell et al., 1996).
N. Feeding Behavior. Larvae are carnivorous, opportunistic predators, consuming small (zooplankton) to large (tadpoles) aquatic and terrestrial prey depending on size and availability. Young larvae use a sit-and-wait technique, lunging at approaching prey. Older larvae stalk or pursue prey (Anderson, 1968). Adults are also carnivorous, preying on a variety of terrestrial organisms, such as annelids, mollusks, and a variety of arthropods: arachnids, coleopterans, collembolans, dipterans, formicids, lepidopterans, and orthopterans (Schonberger, 1944; Farner, 1947; Anderson, 1968). Males feed at breeding sites, taking similar aquatic organisms as larvae (e.g., aquatic dipterans; Anderson, 1968); females do not feed at breeding sites. This difference may result from the longer time males spend at the breeding sites.
O. Predators. Invertebrate predators of larvae include predaceous diving beetles (Dytiscus sp.; Marnell, 1997), odonate naiads, and belostomatids (J.A.F., personal observations). Larvae and adults are also preyed upon by vertebrates, such as salmonid fish (Liss et al., 1995), goldfish (Monello and Wright, 2001), northwestern salamanders (Hoffman and Larson, 1999), blotched tiger salamanders (J.A.F., unpublished data), non-native American bullfrogs (Rana catesbeiana; Nussbaum et al., 1983; M.P. Hayes, personal communication),western terrestrial and common garter snakes (Thamnophis elegans and T. sirtalis, respectively; Ferguson, 1961a; Marnell, 1997; Pilliod, 2001), and belted kingfishers (Ceryle alcyon; P. Murphy, personal communication).
P. Anti-Predator Mechanisms. The highly secretive, subterranean life-style of long-toed salamanders may be one of their most successful avoidance mechanisms (Ferguson, 1961a). However, in the presence of predators, such as tiger salamanders, adult long-toed salamanders may increase their activity and use cover objects less often (J.A.F. and P. Verrell, unpublished data). The yellow dorsal stripe may serve as a warning to predators. When attacks are simulated in a laboratory, long-toed salamanders demonstrate a combination of behavioral and chemical defenses, including coiling, tail undulations and lashing, and production of skin secretions (Anderson, 1963; Brodie, 1977; Williams and Larsen, 1986). Adult long-toed salamanders can vocalize with squeaks and clicks, possibly to startle predators once captured (Hossack, 2002). Adults will avoid areas occupied by a damaged conspecific (Chivers and Kiesecker, 1996), indicating the importance of chemical signals for avoiding predators. Larval long-toed salamanders use chemical cues and learned recognition (non-lethal encounters) to avoid inter- and intraspecific predators (Tyler et al., 1998b; Wildy et al., 2001). The presence of methoxychlor increases vulnerability to predators (Verrell, 2000b).
Q. Diseases. Little is known about the susceptibility of long-toed salamanders to diseases. Two types of water molds, Saprolegnia ferax and Achlya racemosa, have been found growing on long-toed salamander eggs in Montana and Oregon (D.S.P. and others, unpublished data). Water molds, such as Saprolegnia spp., have been reported to increase mortality of injured ambystomatid salamanders (Walls and Jaeger, 1987) and may infect eggs that have been stressed by environmental conditions such as low water levels, cold temperatures, or increased UV-B radiation (Blaustein et al., 1994c; Kiesecker and Blaustein, 1995; Kiesecker et al., 2001a). Investigations into the susceptibility of long-toed salamanders to the recently discovered chytrid fungus are warranted.
R. Parasites. Trematode parasites (Ribeiroia sp.) may be responsible for supernumerary limbs and related deformities observed in > 1,600 long-toed salamanders collected from Oregon in the late 1980s (Sessions and Ruth, 1990; Johnson et al., 1999; Sessions et al., 1999).
4. Conservation. Long-toed salamanders are widespread across their historical range. Santa Cruz long-toed salamanders are Federally listed as Endangered and occur in three population clusters (metapopulations) in coastal areas of Santa Cruz and Monterey counties, California (U.S.F.W.S., 1999). The species is considered “Secure” in Washington, Oregon, Idaho, Montana, and British Columbia according to the National and State Heritage Status Ranks. Long-toed salamanders are on the “Yellow B List” in Alberta, meaning that the species is not at risk but vulnerable to limiting factors such as habitat alteration, destruction of critical habitats, and non-native predatory fish (Graham and Powell, 1999). In Alaska, long-toed salamanders are ranked as “Imperiled” by the State Heritage system, but insufficient information exists to adequately assess the species’ status there.
Long-toed salamanders may suffer local and possibly regional threats, but apparently these threats are not resulting in widespread declines. In the vicinity of urban and agricultural areas, lowland populations may be impacted by the loss of wetlands (Bury and Ruth, 1972; Ruth, 1974, 1988), road mortality during breeding migrations (Fukumoto and Herrero, 1998), chemical contaminants (Ingermann et al., 1997; Fukumoto and Herrero, 1998; Nebeker et al., 1998; Verrell, 2000), and predation from introduced goldfish (Monello and Wright, 2001). In relatively undisturbed mountain habitats, a number of possible threats have been identified, including increased UV-B radiation (Blaustein et al., 1997; Belden et al., 2000; Belden and Blaustein, 2002b), timber harvesting (McGraw, 1998; Naughton et al., 2000), and introduced salmonid fish (Liss et al., 1995; Tyler et al., 1998a; Funk and Dunlap, 1999; Hoffman and Pilliod, 1999; Pilliod and Peterson, 2001), but not increased acid deposition or mobilization of aluminum (Bradford and Gordon, 1992; Bradford et al., 1994c). Elasticity analyses of demographic models for long-toed salamanders suggest that populations are more likely to decline when environmental stressors result in higher mortality of post-metamorphic life stages as compared to stressors that result in mortality of embryos or larvae (Vonesh and De la Cruz, 2002).
Acknowledgments. We thank several people for commenting on this account and providing helpful natural history observations and access to unpublished documents, including J. Howard, B. Leonard, K. McAllister, G. McLaughlin, C. Peterson, L. Powell, and P. Verrell. Support for D.S.P. was provided by USGS Amphibian Research and Monitoring Initiative during the final phase of this project.

Literature references for Amphibian Declines: The Conservation Status of United States Species, edited by Michael Lannoo, are here.

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