Montana Field Guide

EGGS
Laid singly or in small linear clusters of 5 to 120. Each ovum is black or brown above, light gray below, and surrounded by three jelly layers (Micken 1968). Ovum diameters are 2-3 mm (0.08-0.12 in), but total egg diameters, including the three jelly layers, are 7-9 mm (0.3-0.4 in) (Micken 1968, Tanner et al. 1971, Kaplan 1980).

LARVAE
Color is variable, but usually olive green or brown dorsally and silvery white ventrally. Three pairs of external feathery gills emanate from the sides of the head with 15-25 gill rakers on their anterior surface (Russell and Bauer 2000). They are relatively large and heavy-bodied, with a snout-vent length (SVL) of 5-98 mm (0.2-3.9 in) (Kaplan 1980, Hill 1995). Paedomorphs are pond-type larva (but lack balancers), with three large pairs of gills, vomerine teeth in U-shaped pattern, and dorsal fin extending to region of axilla; adults usually are about 15 to 22 cm (5.9-8.7 in) in total length (to about 34 cm or 3.4 in) (Stebbins 1954, 1985, Behler and King 1979, Conant and Collins 1998).

JUVENILES AND ADULTS
Color is variable, but background color is usually dark, with lighter mottling of yellow, tan, or green. Some may be uniformly dark in color (Koch and Peterson 1995). Venter is gray and 12-13 costal grooves are present. Adults are large and heavy-bodied with a SVL 70-90 mm (2.8-3.5 in), have a broad head, small eyes, and tubercles on the soles of the feet (Russell and Bauer 2000).

Long-toed Salamander (A. macrodactylum) eggs have 2 jelly layers and have diameters greater than 10 mm (0.4 in), including the jelly layers. Larval Long-toed Salamanders have smaller heads and are translucent, light tan, or black dorsally and laterally with black and gold flecks. In addition, larval Long-toed Salamanders are white to pinkish ventrally and have 9-13 gill rakers on the anterior surface of their gills.

The Western Tiger Salamander differs from the Long-toed Salamander adults by lacking a distinct dorsal stripe or stripe like row of spots. Western Tiger Salamander differs from all other North American Ambystoma in having tubercles on the soles of the feet. Coeur d'Alene Salamander (Plethodon idahoensis) has a nasolabial groove whcih the Western Tiger Salamander lacks.

Adults may migrate several hundred meters between terrestrial burrows and breeding habitats (Koch and Peterson 1995). Migrations usually occur nocturnally around the time of precipitation events when minimum daily temperatures are greater than 0 °C (32 °F) (Hill 1995).

Adults are found in virtually any habitat, providing there is a terrestrial substrate suitable for burrowing and a body of water nearby suitable for breeding. Terrestrial adults usually remain underground, in self-made burrows or in those made by rodents or other animals (Koch and Peterson 1995, Madison and Farrand 1998). Western Tiger Salamanders in Montana are primarily associated with prairie or agricultural habitats. They breed in ponds, lakes, springs, intermittent streams, and stock ponds. Breeding sites almost always lack predatory fishes and can range from clear mountain ponds to temporary, manure-polluted pools in the lowlands (Micken 1971, USFWS 1964-1982, Baxter and Stone 1985, Hill 1995).

In the water, larvae and adults feed on a variety of aquatic and terrestrial invertebrates. Some larvae and paedomorphic adults feed on other amphibian larvae including conspecifics (Dodson and Dodson 1971, Pfenning et al. 1991). In western Colorado, larvae feed on mostly arthropods. On land, adults may feed on a variety of invertebrates or even small mammals (Moore and Strickland 1955, Petranka 1998). In southern Manitoba, adult diets were found to be 87% Cammarus, 7% Coleoptera, and 8% Hirudinea.

Late metamorphosis probably caused by temperature rather than food abundance. In some locations larval salamanders never transform, but rather become sexually mature and breed while retaining external gills (referred to as neoteny). These salamanders are often called "axolotls" or "water dogs." They are benthic in ponds but may enter upper water column at night. Paedomorphic populations tend to occur at higher elevations. They use behavioral thermoregulation where they tend to select warmest water in ponds (rarely above 25°C or 77 °F). These salamanders use the shallows during day and deep water at night (Heath 1975).

Breeding takes place soon after snow melt. In Montana, breeding often occurs in May on the prairie and June to mid-August at 7780 ft (2371 m) in the southwest. Eggs are attached to submerged objects at shallower depths. Eggs hatch in approximately 15 days from June to August. Larvae may transform at the end of their first summer in August on the prairie but may remain larvae for a second or third summer at high elevations in cold waters (Micken 1968, Hill 1995). Metamorphosed adults may spend extensive periods of time feeding in ponds after breeding. Stays of up to 159 days have been documented in Montana (Hill 1995). In some instances, larvae may become sexually mature (paedogenesis) and reproduce without transforming (Micken 1968, Hill 1995).

The following is taken from the Status and Conservation section for the Western Tiger Salamander account in Maxell et al. 2009.

Western Tiger Salamanders are widely distributed and common on the prairies east of the main Rocky Mountain chain with larvae being found in most fishless ponds with adjacent soils that have not been plowed or otherwise heavily modified. However, their status in the mountains and mountain valleys east of the Continental Divide is largely uncertain. Risk factors relevant to the viability of populations of this species are likely to include grazing, non-indigenous species and their management, road and trail development and on- and off-road vehicle use, development of water impoundments, and habitat fragmentation, all as described above. Individual studies that specifically identify risk factors or other issues relevant to the conservation of Western Tiger Salamanders include the following. (1) Several studies in the western United States over the past five decades have documented the almost complete exclusion of Western Tiger Salamanders from waters were predatory fish have been introduced (Blair 1951, Carpenter 1953c, Levi and Levi 1955, USFWS 1964-1982, Collins et al. 1988, Geraghty 1992, Corn et al. 1997). Furthermore, at least two studies have documented multiple extinction and recolonization events by Western Tiger Salamanders as a result of the introduction, subsequent natural and human caused extinction, and subsequent reintroduction of trout in lakes in Yellowstone and Rocky Mountain National Parks (USFWS 1964-1982, Corn et al. 1997). Even larger larvae, or reproductively mature adults that fish are unable to prey on because of gape limitations are likely to be negatively impacted as a result of fish stocking because the diets of fish and salamanders largely overlap one another (Olenick and Gee 1981). (2) Hamilton (1941) reports that the piscicide rotenone has an LC50 value (i.e., causes 50% mortality) for metamorphosing Western Tiger Salamander larvae when 5% rotenone is applied at 0.1 mg/L for 24 hours. (3) The use of larval Western Tiger Salamanders as bait for sport fishing may have major impacts on Western Tiger Salamander populations and the entire aquatic community at both the site of collection and introduction because of their status as a top-level predator in many aquatic communities (Holomuzki and Collins 1987, Holomuzki et al. 1994). Furthermore, introduction can result in hybridization and genetic introgression with native populations, possibly leading to the elimination of distinct life histories and genetic makeups (Collins 1981, Collins et al. 1988). The bait industry’s use of salamander larvae may be quite extensive. For example, the average number and wholesale value of Western Tiger Salamander larvae in South Dakota wetlands was estimated at 35,625 and $1,614 per hectare, respectively, in 1989 (Carlson and Berry 1990) and Collins (1981) notes that in 1968 2.5 million salamander larvae were sold as bait on the lower Colorado River area alone. (4) Mass mortalities of Western Tiger Salamanders have been observed in agricultural landscapes in eastern Montana (Bryce Maxell, personal observation). Worthylake and Hovingh (1989) documented the recurring mass mortality of Western Tiger Salamanders in lakes contaminated with nitrogen from atmospheric pollution and the feces of sheep. The lakes were previously nitrogen limited and increased nitrogen levels allowed bacterial counts to increase in the summer leading to the mass mortality events. Pfenning et al. (1991) propose that contamination of waters through livestock defecation may alter life histories of Western Tiger Salamanders by limiting the number of cannibal morphs. Cannibal morphs may be more likely to spread pathogens as a result of eating infected conspecifics. Eutrophication of waters through fecal contamination may also cause planorbid snail numbers to rise, thereby increasing the number of nematode parasites and the rate of parasite infection that can subsequently lead to limb deformities (Bishop and Hamilton 1947). Finally, although they have not been linked to water quality, a number of recent mass mortality events have been caused by an iridovirus in the genus, Ranavirus (e.g., Bollinger et al. 1999). (5) Disturbance of terrestrial habitats by plowing and deep raking has been identified as a serious threat to a closely related species, the California Tiger Salamander (Ambystoma californiense) which has recently been emergency listed as a federally endangered species (USDOI 2000). (6) Lefcort et al. (1997) found that waters contaminated with motor oil and silt resulted in decreased growth and survival rates of Western Tiger Salamander larvae as well as decreasing their ability to detect predators. (7) Kiesecker (1996) and Whiteman et al. (1995) documented reduced growth rates, survival rates, predatory success rates, in waters with lower pH (< pH 5.0). Harte and Hoffman (1989) hypothesized that acid precipitation, in the form of an acidic pulse during snow melt, had killed salamander embryos and caused a decline of a population of Western Tiger Salamanders in central Colorado from 1982 to 1987. However, this population has now apparently recovered (Wissinger and Whiteman 1992), and there is little evidence that either chronic or episodic acidification occurs in this area at levels sufficient to directly kill embryos (Corn and Vertucci 1992, Vertucci and Corn 1994, Vertucci and Corn 1996). However, lower pH levels resulting from acidification could act synergistically with pathogens or other contaminants to cause population declines as a result of reduced function of their immune systems (Carey et al. 1999).