Endangered Species in Santa Cruz County - Species Account
Santa Cruz Long-Toed Salamander
(Ambystoma macrodactylum croceum)
The information below is taken from the following publication, which is available for reference use at the Central Branch Library:
- U.S. Fish and Wildlife Service. "Santa Cruz Long-toed Salamander (Ambystoma macrodactylum croceum): Draft Revised Recovery Plan." Portland, Oregon: The Service, 1999.
The Santa Cruz long-toed salamander is federally listed as endangered. It is currently known from three population clusters (metapopulations) in coastal areas of central California's Santa Cruz and Monterey Counties.
Habitat Requirements and Limiting Factors
This salamander inhabits temporary ponds for breeding and adjacent upland scrub and woodland areas during the nonbreeding season. These ponds and adjacent scrub and woodland habitats are restricted naturally to relatively few areas along the central coast of California. Direct habitat loss due to agriculture, urbanization, and road construction is the main cause for this salamander's decline. Other known threats include pollution, siltation, and declining water quality in breeding ponds due to nearby development and agricultural activities; loss of nonbreeding habitat and food resources due to the spread of exotic plants; predation by introduced fishes, bullfrogs, and tiger salamanders; and parasites.
3 on a scale of 1 to 18. The priority is based on its being a subspecies (rather than a full species) with a high degree of threat and high recovery potential. 1
Description and Taxonomy
The Santa Cruz long-toed salamander (Ambystoma macrodactylum croceum) is a small dark-colored salamander of the family Ambystomatidea ... . The adults have an average snout-to-vent length of 42 to 71 millimeters (1.7 to 2.8 inches), with an average total length of 105 to 150 millimeters (4.2 to 6.0 inches). They weigh approximately 3.0 to 9.8 grams (0.1 to 0.4 ounce). This subspecies differs from subspecies A. m. macrodactylum by its dull orange or metallic yellow dorsal markings (a series of discrete, irregular patches on its "back" side), and by greatly reduced dorsal head markings of small scattered dots, which are often absent, anterior to (in front of) the eyes (Ferguson 1961; Stebbins 1966, 1985). The ventral ("stomach") surface is sooty black. The vomerine teeth (located on the roof of the mouth) form a continuous or broken row. Differences in biochemistry (Sage 1978), physiology, and life history traits (Anderson 1960, 1967, 1968a, 1968b, 1972a, 1972b, 1972c) support the separation of A. m. croceum as a distinct species. However, until a more thorough investigation of the genetics of the species is conducted and a revision of the taxonomy published in a peer-reviewed journal, Santa Cruz long-toed salamanders will continue to be considered a subspecies of long-toed salamander (A. macrodactylum).
Life History and Ecology
The Santa Cruz long-toed salamander spends a substantial portion of its life underground in small mammal burrows. Examples of the small mammal burrows include mice (Peromyscus spp.), California voles (Microtus californicus), Botta pocket gophers (Thomomys bottae), and California moles (Scapanus latimanus). This salamander is also found among the root systems of plants in upland chaparral and woodland areas of coast live oak (Quercus agrifolia) or Monterey pine (Pinus radiata), and in strips of riparian vegetation such as arroyo willows (Salix lasiolepis), cattails (Typha spp.), and bulrush (Scirpus spp.). These areas are desirable because they are protected from heat and the drying rays of the sun (Reed 1979, 1981). The soils associated with these plant communities are usually sandy loams formed on old dune deposits, marine terraces, or alluvium deposits (Cook 1978, Bowman and Estrada 1980). 2
Adult Santa Cruz long-toed salamanders leave their upland chaparral and woodland summer retreats at the onset of the rainy season in mid- to late-November or December, and begin their annual nocturnal migration to the breeding ponds (Anderson 1960). They often forage for invertebrates on the soil surface -- primarily isopods, but also beetles, slugs and earthworms (Anderson 1968b). Adult Santa Cruz long-toed salamanders migrate primarily on nights of rain, mist, or heavy fog (Anderson 1960, 1967; Ruth and Tollestrup 1973; Reed 1979, 1981). They arrive at the breeding ponds from November through March, with most arrivals occurring in January and February (Anderson 1967, Reed 1979, Ruth 1988b). Peak breeding occurs during January and February because earlier rains are usually insufficient to fill the breeding ponds (Anderson 1967). Adults may skip breeding for one or more years if little or no surface water is present (Russell and Anderson 1956). Males usually migrate to pond sites 1 to 2 weeks before the females (Reed 1979, 1981; Ruth 1988a), although they may move up to 6 weeks earlier depending on rainfall patterns (Ruth and Tollestrup 1973). As female salamanders enter the pond, they pair with males, court, and breed (Anderson 1961, 1967; Reed 1979, 1981). Males apparently remain in ponds twice as long (1 to 5 weeks) as females (Ruth 1988a) and may successfully breed with more than one female each season (Reed 1981). Sex ratios of sampled populations vary depending on site, time of year, and distance from the pond. However, most studies using standard mark-recapture methods have found sex ratios of one to two males per female at the breeding sites, with more females found farther from the ponds (0.6 males per female) (Reed 1981; Ruth 1988b, 1994).
Female Santa Cruz long-toed salamanders have specialized and selective egg-laying habits. Eggs are laid singly on submerged stalks of spikerush (Eleocharis spp.) or other vegetation about 2 to 3 centimeters (1 inch) apart (Anderson 1960, 1967). Unattached and clustered eggs have also been observed (Reed 1981). Each female lays about 300 (range 215 to 411) eggs per year (Anderson 1967).
After courtship and egg laying, most adult Santa Cruz long-toed salamanders leave the pond in March or April and return to the same general upland areas where they spent the previous summer, often foraging while en route. Some adults may remain in the vicinity of the breeding site for a year or more before returning to more distant terrestrial retreats (Ruth 1988b). The eggs and larvae are unattended by the adults.
Eggs usually hatch after 15 to 30 days into the aquatic larval stage (Reed 1979, 1981; Ruth 1988a); the actual development time depends on water temperature (Anderson 1972b). The larvae, which subsist largely on aquatic invertebrates such as mosquito larvae and worms, as well as larval amphibians (e.g., Pacific treefrogs [Hyla regilla] and salamander larvae) (Anderson 1968b), remain in the pond environment for 90 to 145 days until they reach about 32 millimeters (1.3 inches) snout to vent length (Anderson 1960). However, the body size at initiation of metamorphosis is variable, ranging from 26 to 48 millimeters (1.0 to 1.8 inches) snout to vent length (Anderson 1967, Reed 1981, Ruth 1988b). Metamorphosis may extend from early May to mid-August, but all of the larvae may metamorphose in a relatively short period of time if the pond environmnet becomes unsuitable (Anderson 1967; Ruth and Tollestrup 1973; Reed 1979, 1981; Ruth 1988a). 3
As the ponds begin to dry, juvenile Santa Cruz long-toed salamanders move at night and may seek refuge underground, in litter at the pond site, or in adjacent willow stands (Anderson 1967; Reed 1979, 1981). However, Andoli (1995) and Jennisngs (1995) found that most juvenile Santa Cruz long-toed salamanders moved at least 30 to 60 meeters (100 to 200 feet) from the breeding pond during the initial migration phase. In their studies, migration was associated with unusual heavy rains in mid-June. During the next rainy season, the juveniles disperse farther away from the pond, not returning until they reach sexual maturity at 2 to 3 years (Ruth 1988a). Anderson (1967) reported minimum adult size (snout to vent length) as 52 millimeters (2.1 inches) for females and 46 millimeters (1.8 inches) for males. Reed (1981) reported minimum adult size as 42 millimeters (1.7 inches), and Ruth (1994) reported minimum adult size of 52 millimeters (2.1 inches). Few data exist regarding dispersal movements of juveniles, foraging ecology, habitat use, or movements of adult salamanders during the nonbreeding season.
Santa Cruz long-toed salamanders apparently are long-lived creatures, possibly living for a decade or more. An adult Santa Cruz long-toed salamander confiscated by law enforcement officials was kept in captivity for more than 8 years until its death (S. B. Ruth, in litt., 1998). Adults of the closely related southern long-toed salamander (A. m. sigillatum) have lived more than 6 years in captivity (Snider and Bowler 1992), and the eastern long-toed salamander (A. m. krausei) have known to survive 10 years in the wild (Russell et al. 1995). 4
Distribution and Population Status
The Santa Cruz long-toed salamander is a relict form of a species that probably was widespread throughout much of California during and immediately after the last Pleistocene ice advance, 10,000 to 12,000 years ago (Ruth and Tollestrup 1973). Scientists believe that during climatic changes and drying conditions in California following the end of the Pleistocene epoch (Stebbins 1949, Raven and Azelrod 1978), a population of the ancestral salamander species became isolated in the area of present-day Santa Cruz, California, about 840 kilometers (520 miles) south of the nearest coastal population of the long-toed salamander and about 240 kilometers (150 miles) southwest of the nearest Sierra Nevada population (Russell and Anderson 1956). In adapting to the very different conditions, far from the main range of long-toed salamanders, the Santa Cruz population evolved during the last several thousand years into a distinct subspecies. 5
Based on the available survey data, the Santa Cruz long-toed salamander's distribution appears to consist of three metapopulations, each with one or more subpopulations, inhabiting one or more ponds or sloughs and the surrounding upland habitats. The metapopulations originally may have been separated by unsuitable habitat consisting of large rivers and sloughs, or extensive areas of coastal scrub and grasslands. Today, the Pajaro River and Elkhorn Slough act as bariers between metapopulations, as do extensive areas of agriculture. The subpopulations within the complexes (the ponds and upland habitats that harbor subpopulations ...) are focused around individual breeding ponds or clusters of ponds. Areas of suitable riparian and woodland vegetation between ponds within complexes allow Santa Cruz long-toed salamanders to move between ponds and to locate new ponds as they became available. However, much of this habitat has been lost to agriculture, urbanization and highway construction.
The northern or Santa Cruz County metapopulation (consisting of four currently recognized subpopulations) appears to be restricted to the area bounded by Valencia Creek on the north, Corralitos Creek on the east, the Pajaro River on the south, and the Pacific Ocean on the west. The central or McClusky Slough metapopulation is found in the region between the Pajaro River and Elkhorn Slough, and the southern or Moro Cojo metapopulation located between Elkhorn Slough and the Salinas River. In the central and southern metapopulations, the known breeding sites are very close to each other, so these metapopulations cannot be subdivided into distinct subpopulations, based on current knowledge or salamander movements. Further surveys in suitable habitats may find new subpopulations or metapopulations.
It is important to maintain connectivity between breeding ponds within subpopulation ranges and between adjacent subpopulations. If one or more breeding aggregations within a subpopulation, or subpopulations, becomes extirpated due to a catastrophic event, then individuals from nearby aggregations or subpopulations can recolonize the site when wuitable habitat becomes available, or colonize any new habitats that are created. The cycle of continuous extinction and recolonization events in suitable habitats is a common theme for ambystomatid salamanders (Shaffer et al. 1993). 6
Reasons for Declines and Current Threats
Climate changes and geologic activity in California over the last 10,000 to 12,000 years have led to a restricted and patchy distribution of habitat suitable for Santa Cruz long-toed salamanders, resulting in a naturally restricted distribution of the subspecies. The disjunct distribution of the subpopulations has made the Santa Cruz long-toed salamander especially susceptible to population declines resulting from both human-associated and natural factors. The factors include habitat loss and degradation, collection, predation by introduced and native organisms, infestations of parasites, geologic processes, and weather conditions. In Santa Cruz County, the primary threats have been road construction and urbanization. In the past, agriculture conducted at relatively low intensity apparently did not severely reduce the subpopulation sizes nor the extent or quality of available habitat. Today in Monterey County, the primary causes for decline are extensive and intensive agricultural practices and urbanization. 7
2 Ibid., p. 4.
3 Ibid., pp. 6-8.
4 Ibid., pp. 8-9.
5 Ibid., p. 10.
6 Ibid., pp. 11-12.
7 Ibid., p. 25.