Federal Register: May 23, 2003 (Volume 68, Number 100)
DOCID: FR Doc 03-12695
DEPARTMENT OF THE INTERIOR
CFR Citation: 50 CFR Part 17
RIN ID: RIN 1018-AI68
NOTICE: Part IV
DOCUMENT ACTION: Proposed rule and notice of public hearing.
Endangered and Threatened Wildlife and Plants; Listing of the Central California Distinct Population Segment of the California Tiger Salamander; Reclassification of the Sonoma County and Santa Barbara County Distinct Populations From Endangered to Threatened; Special Rule
DATES: Comments: We must receive comments from all interested parties by 5 p.m. on July 22, 2003.
Public Hearings: We will hold public hearings at the following times:
(1) Tuesday, June 17, 2003Livermore, California. Two sessions, 1 p.m. until 3 p.m. and 6 p.m. until 8 p.m. Registration will begin at 12:30 p.m. for the afternoon session and at 5:30 p.m. for the evening session.
(2) Wednesday, June 18, 2003Monterey, California. Two sessions, 1 p.m. until 3 p.m. and 6 p.m. until 8 p.m. Registration will begin at 12:30 p.m. for the afternoon session and at 5:30 p.m. for the evening session.
(3) Thursday, June 19, 2003Merced, California. Two sessions, 1 p.m. until 3 p.m. and 6 p.m. until 8 p.m. Registration will begin at 12:30 p.m. for the afternoon session and at 5:30 p.m. for the evening session.
Public informational meetings also will be held in California in various locations, with sites and dates publicized through local news media. See ADDRESSES section for specific location information of the hearings identified above and see ``Public Hearings'' under SUPPLEMENTARY INFORMATION for general information.
We, the Fish and Wildlife Service (Service), propose threatened status for the Central California distinct population segment (DPS) of the California tiger salamander (Ambystoma californiense), pursuant to the Endangered Species Act of 1973, as amended (Act). The Santa Barbara County and Sonoma County DPSs are listed as endangered. We propose reclassifying these populations as threatened. This proposal, if made final, would extend the Federal protection and recovery provisions of the Act to the Central California DPS of this species.
A special rule is also being proposed to exempt existing routine ranching activities from the prohibitions of the Act because these practices have neutral or beneficial effects on the California tiger salamander. We solicit additional data and information that may assist us in making a final decision on this proposed action.
Interior Department, Fish and Wildlife Service,
Previous Federal Action
On September 18, 1985, we published the Vertebrate Notice of Review (NOR) (50 FR 37958), which included the California tiger salamander as a category 2 candidate species for possible future listing as threatened or endangered. Category 2 candidates were those taxa for which information contained in our files indicated that listing may be appropriate but for which additional data were needed to support a listing proposal. The January 6, 1989, and November 21, 1991, NORs (54 FR 554 and 56 FR 58804, respectively) also included the California tiger salamander as a category 2 candidate and solicited information on the status of the species.
On February 21, 1992, we received a petition to list the California tiger salamander as an endangered species from Dr. H. Bradley Shaffer at University of California, Davis. We published a 90day petition finding on November 19, 1992 (57 FR 54545), concluding that the petition presented substantial information indicating that listing may be warranted. On April 18, 1994, we published a 12month petition finding (59 FR 18353) that the listing of the California tiger salamander was warranted but precluded by higher priority listing actions. We elevated the species to category 1 status at that time, which was reflected in the November 15, 1994, NOR (59 FR 58982). Category 1 candidates were those taxa for which we had on file sufficient information on biological vulnerability and threats to support preparation of listing proposals.
We discontinued the use of different categories of candidates in the February 28, 1996, NOR (61 FR 7596), and defined ``candidate species'' as those meeting the definition of former category 1. We maintained the California tiger salamander as a candidate species in that NOR, as well as in subsequent NORs published September 19, 1997 (62 FR 49398), October 25, 1999 (64 FR 57533), and October 30, 2001 (66 FR 54808).
On January 19, 2000, we published an emergency rule to list the Santa Barbara County DPS of the California tiger salamander as endangered (65 FR 3096), concurrently with a proposed rule (65 FR 3110) to list the same DPS as endangered. On September 21, 2000, we listed the Santa Barbara County DPS of the California tiger salamander as endangered (65 FR 57242).
On June 12, 2001, we received a petition dated June 11, 2001, from
the Center for Biological Diversity (CBD) and Citizens for a
Sustainable Cotati to emergencylist the Sonoma County DPS of the
California tiger salamander as an endangered species and to designate
critical habitat. On February 27, 2002, the CBD filed a complaint in
the Northern District of California for our failure to list the Sonoma
County DPS of the California tiger salamander as endangered (Center for
Biological Diversity v. U.S. Fish and Wildlife Service (Case No. C02
0558)). On June 6, 2002, based on a settlement agreement with the CBD,
the court issued an order requiring us to submit for Federal Register
publication a proposal and/or emergency rule to list the Sonoma County
DPS by July 15, 2002. We were also to submit for publication in the
Federal Register a proposal to list the California tiger salamander
throughout the remainder of its range (except for the Santa Barbara
County and Sonoma County DPSs) on or before May 15, 2003, and to publish a
final rule on or before May 15, 2004. On July 22, 2002, the Sonoma County DPS was listed as an endangered species under an emergency basis and proposed for listing as endangered (67 FR 47726; 67 FR 47758). The final rule listing the Sonoma County DPS as endangered was published in the Federal Register on March 19, 2003 (68 FR 13498). This proposed rule to list the Central California tiger salamander complies with the June 6, 2002, settlement agreement.
The California tiger salamander was first described as Ambystoma californiense by Gray in 1853 based on specimens that had been collected in Monterey, California (Grinnell and Camp 1917). Storer (1925) and Bishop (1943) also considered the California tiger salamander to be a distinct species. Dunn (1940), Gehlbach (1967), and Frost (1985) stated the California tiger salamander was a subspecies of the more widespread tiger salamander (A. tigrinum). However, based on recent studies of the genetics, geographic distribution, and ecological differences among the members of the A. tigrinum complex, the California tiger salamander is now considered to be a distinct species (Shaffer and Stanley 1991; Jones 1993; Shaffer et al. 1993; Shaffer and McKnight 1996; Irschick and Shaffer 1997; Petranka 1998). The range of this animal does not naturally overlap with any other species of tiger salamander (Stebbins 1985; Petranka 1998).
The California tiger salamander is a large and stocky terrestrial salamander with small eyes and a broad, rounded snout. Adults may reach a total length of 208 millimeters (mm) (8.2 inches (in)), with males generally averaging about 203 mm (8 in) in total length, and females averaging about 173 mm (6.8 in) in total length. For both sexes, the average snoutvent length is approximately 91 mm (3.6 in). The small eyes have black irises and protrude from the head. Coloration consists of white or pale yellow spots or bars on a black background on the back and sides. The belly varies from almost uniform white or pale yellow to a variegated pattern of white or pale yellow and black. Males can be distinguished from females, especially during the breeding season, by their swollen cloacae (a common chamber into which the intestinal, urinary, and reproductive canals discharge), moredeveloped tail fins, and larger overall size (Stebbins 1962; Loredo and Van Vuren 1996).
California tiger salamanders are restricted to vernal pools and seasonal ponds in grassland and oak savannah plant communities from sea level to about 460 meters (m) (1,500 feet (ft)) (Stebbins 1989; Shaffer et al. 1993; Jennings and Hayes 1994; Petranka 1998; California Natural Diversity Data Base (CNDDB) 2002). Along the coast ranges, the species occurs in the Santa Rosa area of Sonoma County, southern San Mateo County south to central San Luis Obispo County, and the vicinity of northwestern Santa Barbara County. In the Central Valley and surrounding Sierra Nevada foothills, the species occurs from northern Yolo County (Dunnigan) southward to northwestern Kern County and northern Tulare County. A population of salamanders at Grass Lake in Siskiyou County (Mullen and Stebbins 1978) has been identified as the northwestern tiger salamander (A. t. melanostictum) (H. Shaffer, University of California, Davis, pers. comm. 1998).
Several gaps exist in the distribution of the California tiger salamander. In the northeastern Sacramento Valley, the species was known from only one site, in southern Butte County on the Gray Lodge Waterfowl Management Area, where it has not been located since 1965 despite subsequent surveys (Stebbins 1989; Shaffer et al. 1993). Although the area between Sacramento and the Cosumnes River contains suitable vernal pools, and has been surveyed extensively, the species has only been recorded along the southern edge of Sacramento County (CNDDB 2002). In a survey transect that extended along the west side of the Sacramento Valley from Shasta County to Solano County, and contained 35 kilometers (km) (22 miles (mi)) of vernal pool habitat and over 200 pools, California tiger salamanders were recorded only at the Jepson Prairie in Solano County (Simovich et al. 1993). The animal has not been found west of Interstate Highway 680 and north of Interstate Highway 580 in Contra Costa or Alameda Counties (LSA Associates, Inc. 2001; CNDDB 2002). It is likely that the species is uncommon or absent in much of the southernmost San Joaquin Valley from approximately Los Banos in Merced County south, and the foothills of the Sierra Nevada south of Visalia in Tulare County, because of unsuitable habitat (Shaffer et al. 1993). The factors that may restrict the California tiger salamander in the northern and southern extent of its range are speculative (H. Shaffer, pers. comm. 2002), but may include low rainfall in the southern San Joaquin Valley and the greater abundance of nonnative predatory fish in the northern Sacramento Valley (Hayes 1977). Jones (1989) suggests that the present pattern of disjunct and widely dispersed populations was caused by the extreme anthropogenic changes in and around the Central Valley, and by the restrictive breeding requirements of the species.
Studies of mitochondrial DNA (mtDNA) indicate that there are six populations of A. californiense, which are found in Sonoma County, Santa Barbara County, the Bay Area (central and southern Alameda, Santa Clara, western Stanislaus, western Merced, and the majority of San Benito Counties), Central Valley (Yolo, Sacramento, Solano, eastern Contra Costa, northeast Alameda, San Joaquin, Stanislaus, Merced, and northwestern Madera Counties), southern San Joaquin Valley (portions of Madera, central Fresno, and northern Tulare and Kings Counties), and the Central Coast Range (southern Santa Cruz, Monterey, northern San Luis Obispo, and portions of western San Benito, Fresno, and Kern Counties) (Shaffer and Trenham 2002). Except for the Sonoma County and Santa Barbara County populations, the geographic barriers between some of these populations are not entirely clear. The Central California DPS of the California tiger salamander (Central California tiger salamander) occupies the Bay Area, Central Valley, southern San Joaquin Valley, and the Central Coast Range.
Subadult and adult California tiger salamanders spend the dry summer and fall months of the year estivating (existing in a state of dormancy or inactivity in response to hot, dry weather) in the burrows of small mammals, such as California ground squirrels (Spermophilus beecheyi) and Botta's pocket gopher (Thomomys bottae) (Storer 1925; Loredo and Van Vuren 1996; Petranka 1998; Trenham 1998a). During estivation, California tiger salamanders eat very little (Shaffer et al. 1993). Once fall or winter rains begin, they emerge from the upland sites on rainy nights to feed and to migrate to the breeding ponds (Stebbins 1985, 1989; Shaffer et al. 1993).
California tiger salamanders spend the vast majority of their lives in upland habitats, and cannot persist without it. The upland component of California tiger salamander habitat typically consists of grassland savannah with scattered oak trees. However, in Santa Barbara County, some California tiger salamander breeding ponds exist within mixed grassland and woodland habitats, and a few ponds are found in woodlands, scrub, or chaparral habitats. Salamanders settle most commonly in burrows in open grassland or under isolated oaks, and less commonly in oak woodlands.
The salamanders breeding in, and living around, a seasonal pool or pools, and associated uplands where estivation can occur, are said to occupy a breeding site. A breeding site is defined as a location where the animals are able to successfully breed in years of ``normal'' rainfall and complete their estivation. Historically, California tiger salamanders utilized vernal pools, but the species will also breed in stockponds.
Occurrence of California tiger salamanders is significantly associated with occurrence of California ground squirrels (Seymour and Westphal 1994). Active ground burrowing rodent colonies probably are required to sustain California tiger salamanders because inactive burrow systems become progressively unsuitable over time. Loredo et al. (1996) found that California ground squirrel burrow systems collapsed within 18 months following abandonment by, or loss of, the mammals. Although California tiger salamanders use both occupied and unoccupied burrows, they apparently do not use collapsed burrows.
Adult California tiger salamanders may migrate up to 1.6 km (1 mi) from their upland sites to the breeding ponds (S. Sweet, University of California, Santa Barbara, in litt. 1998), which may be vernal pools, stockponds, or other seasonal water bodies. The distance between the upland sites and breeding pools depends on local topography and vegetation, and the distribution of California ground squirrel or other rodent burrows (Stebbins 1989). Males migrate to the breeding ponds before females (Twitty 1941; Shaffer, et al. 1993; Loredo and Van Vuren 1996; Trenham 1998b). Males usually remain in the ponds for an average of about 6 to 8 weeks, while females stay for approximately 1 to 2 weeks. In dry years, both sexes may stay for shorter periods (Loredo and Van Vuren 1996; Trenham 1998b). Most marked salamanders have been recaptured at the pond where they were initially captured; in one study, approximately 80 percent were recaptured at the same pond (Trenham 1998b). The rate of natural movement of salamanders among breeding sites depends on the distance between the ponds or complexes of ponds and on the quality of intervening habitat (e.g., salamanders may move more quickly through sparsely covered and open grassland than they can through densely vegetated lands) (Trenham 1998a). As with migration distances, the number of ponds used by an individual over its lifetime depends on landscape features and environmental factors.
The adults mate in the ponds and the females lay their eggs in the water (Twitty 1941; Shaffer et al. 1993; Petranka 1998). Females attach their eggs singly or, in rare circumstances, in groups of two to four, to twigs, grass stems, vegetation, or debris (Storer 1925; Twitty 1941). In ponds with no or limited vegetation, females may attach eggs to objects, such as rocks and boards on the bottom (Jennings and Hayes 1994). After breeding, adults leave the pool and return to the small mammal burrows (Loredo et al. 1996; Trenham 1998a), although they may continue to come out nightly for approximately the next 2 weeks to feed (Shaffer et al. 1993). In drought years, the seasonal pools may not form and the adults cannot breed (Barry and Shaffer 1994).
Salamander eggs hatch in 10 to 14 days with newly hatched salamanders (larvae) ranging in size from 11.5 to 14.2 mm (0.45 to 0.55 in) in total length (Petranka 1998). The larvae are aquatic. Each is yellowish gray in color and has a broad fat head, large, feathery external gills, and broad dorsal fins that extend well onto its back. The larvae feed on zooplankton, small crustaceans, and aquatic insects for about 6 weeks after hatching, after which they switch to larger prey (J. Anderson 1968). Larger larvae have been known to consume smaller tadpoles of Pacific treefrogs (Pseudacris regilla) and California redlegged frogs (Rana aurora) (J. Anderson 1968; P. Anderson 1968). The larvae are among the top aquatic predators in the seasonal pool ecosystems. They often rest on the bottom in shallow water, but also may be found at different layers in the water column in deeper water. The young salamanders are wary; when approached by potential predators, they will dart into vegetation on the bottom of the pool (Storer 1925).
The larval stage of the California tiger salamander usually lasts 3 to 6 months, because most seasonal ponds and pools dry up during the summer (Petranka 1998). Amphibian larvae must grow to a critical minimum body size before they can metamorphose (change into a different physical form) to the terrestrial stage (Wilbur and Collins 1973). Individuals collected near Stockton in the Central Valley during April varied from 47 to 58 mm (1.85 to 2.3 in) in length (Storer 1925). Feaver (1971) found that larvae metamorphosed and left the breeding pools 60 to 94 days after the eggs had been laid, with larvae developing faster in smaller, more rapidly drying pools. The longer the ponding duration, the larger the larvae and metamorphosed juveniles are able to grow, and the more likely they are to survive and reproduce (Semlitsch et al. 1988; Pechmann et al. 1989; Morey 1998; Trenham 1998b). The larvae perish if a site dries before they complete metamorphosis (P. Anderson 1968; Feaver 1971). Pechmann et al. (1989) found a strong positive correlation between ponding duration and total number of metamorphosing juveniles in 5 salamander species. In Madera County, Feaver (1971) found that only 11 of 30 pools sampled supported larval California tiger salamanders, and 5 of these dried before metamorphosis could occur. Therefore, out of the original 30 pools, only 6 (20 percent) provided suitable conditions for successful reproduction that year. Size at metamorphosis is positively correlated with stored body fat and survival of juvenile amphibians, and negatively correlated with age at first reproduction (Semlitsch et al. 1988; Scott 1994; Morey 1998).
The metamorphosed juveniles leave their ponds in the late spring or early summer. Before the pools dry completely, they settle in small mammal burrows, to which they return at the end of nightly movements (Zeiner et al. 1988; Shaffer et al. 1993; Loredo et al. 1996). Like the adults, juveniles may emerge from these retreats to feed during nights of high relative humidity (Storer 1925; Shaffer et al. 1993) before settling in their selected upland sites for the dry, hot summer months. Juveniles have been observed to migrate up to 1.6 km (1 mi) from breeding pools to upland areas (Austin and Shaffer 1992).
An estimated 83 percent of the salamanders rely on rodent burrows for shelter (Petranka 1998). Mortality of juveniles during their first summer exceeds 50 percent (Trenham 1998b). Emergence from upland estivation sites in hot, dry weather occasionally results in mass mortality of juveniles (Holland et al. 1990). Juveniles do not typically return to the breeding pools until they reach sexual maturity, at several years of age (Trenham 1998b; Hunt 1998). Trenham (1998b) estimated survival from metamorphosis to maturity at his study site to be less than 5 percent (well below an estimated replacement level of 18 percent). Adult survivorship varies greatly between years, but is a crucial determinant of whether a population is a source or sink (i.e., whether net productivity exceeds the level necessary to maintain the population or it does not).
Lifetime reproductive success for California and other tiger
salamanders is low. Trenham et al. (2000) found the average female bred
1.4 times and produced 8.5 young that survived to metamorphosis per reproductive effort. This resulted in roughly 11
metamorphic offspring over the lifetime of a female. Preliminary data suggest that most California tiger salamander individuals require 2 years to become sexually mature. But some individuals may be slower to mature (Shaffer et al. 1993), and some animals do not breed until they are 4 to 6 years old. While individuals may survive for more than 10 years, many breed only once, and in some populations, less than 5 percent of marked juveniles survive to become breeding adults (Trenham 1998b). With such low recruitment, isolated populations can decline greatly resulting from unusual, randomly occurring natural events, as well as from humancaused factors that reduce breeding success and individual survival. Factors that repeatedly lower breeding success in isolated pools that are located too far from other pools to allow migrating individuals to replenish the population can quickly extirpate a population.
The life history and ecology of the California tiger salamander make it likely that this population has a metapopulation structure (Hanski and Gilpin 1991). A metapopulation is a set of local populations or breeding sites within an area, where typically migration from one local population or breeding site to other areas containing suitable habitat is possible, but not routine. Dispersal (movement between areas containing suitable habitat) is restricted by inhospitable conditions around and between areas of suitable habitat. Because many of the areas of suitable habitat may be small and support small numbers of salamanders, local extinction may commonly occur. A metapopulation's persistence depends on the combined dynamics of these local extinctions and the subsequent recolonization of these areas through dispersal (Hanski and Gilpin 1991; Hanski 1994; McCullough 1996).
The total number of individual California tiger salamanders is not known. The difficulty of estimating total California tiger salamander population size has been discussed by a number of biologists (Shaffer et al. 1993; Jennings and Hayes 1994). However, estimates have been made for a few populations in Monterey (Trenham et al. 2000; Barry and Shaffer 1994). Because data on numbers of individual California tiger salamanders are lacking, since they spend much of their lives underground, and because only a portion of the total number of animals migrate to pools to breed each year (Trenham et al. 2000), the availability of suitable habitat and documentation of its loss may be an appropriate method for assessing the status of the species.
Vernal pools and other seasonal ponds are the primary breeding areas used by California tiger salamanders (Storer 1925; Feaver 1971; Zeiner et al. 1988). The species occurs in 10 of the 17 Californian vernal pool regions defined by KeelerWolf et al. (1998), including northeastern Sacramento Valley, southeastern Sacramento Valley, Santa Rosa, SolanoColusa, Livermore, Central Coast, Carrizo, southern Sierra Foothills, Santa Barbara, and San Joaquin Valley. Vernal pools typically form in topographic depressions underlain by an impervious layer (such as claypan, hardpan, or volcanic strata) that prevents downward percolation of water. Vernal pool hydrology is characterized by ponding of water during the late fall, winter, and spring, followed by complete desiccation during the summer dry season (Holland and Jain 1998). Vernal pools support diverse flora and fauna that are adapted to the dramatic seasonal changes in moisture and benefit from the lack of predation by nonnative fish. Thirty other federally or State listed species within the California tiger salamander's range are vernal pool specialists, including 24 plants, 4 crustaceans, and 1 insect (Keeler Wolf et al. 1998). California tiger salamanders, like the listed vernal pool crustaceans, prefer seasonally ponded habitat. However, listed vernal pool crustaceans require only a few weeks of inundation to complete their life cycle (59 FR 48136; September 19, 1994); therefore, pools that support crustacean populations may not hold water long enough to allow successful metamorphosis of California tiger salamander larvae.
In addition to vernal pools and seasonal ponds, California tiger salamanders also use small artificial water bodies for breeding (Stebbins 1985; Zeiner et al. 1988; Shaffer et al. 1993). Stockponds for cattle (Bos taurus), sheep (Ovies aries), horses (Equus caballus) and other livestock have been, and continue to be, built to supply local water needs, especially in rural grazing lands in coastal and Sierra foothill areas where inexpensive public water or ground water is not available (Bennett 1970). Stockponds, constructed as water sources for livestock, are important habitats for the California tiger salamander throughout its range (H. Shaffer, pers. comm. 2003; P. Trenham, University of California, Davis, pers. comm. 2002). A large population of the California tiger salamander coexists with sheep and horses at the University of California Natural Reserve System's Jepson Prairie in Solano County (P. Trenham, pers. comm. 2002; CNDDB 2002). In some areas, stockponds have largely replaced vernal pools and provide important habitat for the species. For instance, of the 112 California tiger salamander locality records in the Livermore area where the wetland type was identified, 88 percent (98 sites) are located in stockponds (CNDDB 2002).
However, stockponds often are poorer habitat for California tiger salamanders than natural vernal pools. Hydroperiods (amount of time the stockpond contains water) may be so short that larvae cannot metamorphose (e.g., when early drawdown of irrigation ponds occurs), or so long that predatory fish and bullfrogs R. catesbeiana) can colonize the pond (Shaffer et al. 1993; Seymour and Westphal 1994). Permanent wetlands may occasionally support breeding California tiger salamanders if fish are not present, but extirpation of the salamander population is likely if fish are introduced (Shaffer et al. 1993; Seymour and Westphal 1994). Artificial ponds also require ongoing maintenance and are often temporary structures. Natural soil erosion, sometimes increased by pond breaching, stock animal impacts, and offroad vehicle (ORV) use, can cause ponds to silt in after a few decades (Hamilton and Jepson 1940), thereby reducing their quality as salamander habitat. Often ponds are not maintained because it may be more economical to construct a new pond when the old pond fills with silt and is no longer functional (Hamilton and Jepson 1940). Stockponds are often geographically isolated from other seasonal wetlands occupied by California tiger salamanders, and colonization of newly created ponds beyond the normal dispersal range may be slow or nonexistent (Pechmann et al. 1989).
Although stockponds can provide refugia for salamander populations
and are important for the species, these habitats may be dynamic.
Stockponds often dry out during drought, and flooding may destroy
downstream impoundments or cause siltation, either of which may result
in loss of aquatic habitat and extirpation of salamander populations.
Periodic maintenance to remove silt from stockponds may also cause a
temporary loss of habitat. Some eggs and larvae of the California tiger
salamander are probably trampled by livestock on the perimeters of the
stockponds. Populations of nonnative introduced predaceous fish and
bullfrogs, although less prevalent than in natural habitats, sometimes
become established in stockponds and have been implicated in the decline of the
California tiger salamander (Fisher and Shaffer 1996).
Stockponds may also facilitate spread of nonnative organisms by providing aquatic habitats in arid landscapes that otherwise may have served as barriers to the spread of such organisms. Despite these adverse impacts, the longterm effect of ranching on the species is either neutral or beneficial, because the California tiger salamander would have likely been extirpated from many areas if stockponds had not been built and maintained for livestock production.
Distinct Vertebrate Population Segment
Under the Act, we must consider for listing any species, subspecies, or, for vertebrates, DPSs of these taxa, if information is sufficient to indicate that such action may be warranted. To implement the measures prescribed by the Act and its Congressional guidance, we, along with the National Oceanic and Atmospheric Administration (NOAA) Fisheries, developed policy that addresses the recognition of DPSs for potential listing actions (61 FR 4722; February 7, 1996). The policy allows for a more refined application of the Act that better reflects the biological needs of the taxon being considered, and avoids the inclusion of entities that do not require its protective measures. Under our DPS policy, we use two elements to assess whether a population segment under consideration for listing may be recognized as a DPS. The elements are: (1) the population segment's discreteness from the remainder of the species to which it belongs; and (2) the significance of the population segment to the species to which it belongs. If we determine that a population segment being considered for listing is a DPS, then we evaluate the level of threat to that population segment on the basis of the five listing factors established by the Act to determine if listing it as either threatened or endangered is warranted.
The DPS policy's standard for discreteness is meant to allow an entity given DPS status under the Act to be adequately defined and described. A population segment of a vertebrate species may be considered discrete if it satisfies either one of the following two conditions: (1) it is markedly separated from other populations of the same taxon as a consequence of physical, physiological, ecological, or behavioral factors. Quantitative measures of genetic or morphological discontinuity may provide evidence of this separation; or (2) it is delimited by international governmental boundaries within which significant differences in control of exploitation, management of habitat, conservation status, or regulatory mechanisms exist.
Dr. H. Bradley Shaffer has analyzed the population genetics of the California tiger salamander (Shaffer et al 1993; Shaffer and Trenham 2002). The most recently available and most comprehensive mtDNA sequence data indicate that there are six populations of California tiger salamander; these six populations are distinguished from one another by their mtDNA characteristics (Shaffer and Trenham 2002). We based our DPS determinations for the alreadylisted Sonoma County and Santa Barbara County populations of the California tiger salamander in part on the relatively high divergence of these populations from other populations of California tiger salamanders (65 FR 57242; 68 FR 13498). The phylogenetic tree (which indicates relationships among populations or groups) constructed from the mtDNA data of Shaffer and Trenham (2002) indicates that Sonoma County and Santa Barbara County California tiger salamanders are very distinct relative to other California tiger salamanders. They are separated from other California tiger salamanders on branches that are statistically strongly supported. These data indicate that Sonoma County and Santa Barbara County California tiger salamanders are distinct from other populations of the species. The genetic differentiation observed indicates that there has been little, if any, gene flow for a significant period of time between the Sonoma County population, the Santa Barbara County population, and the remaining populations, which are the subject of this rulemaking process.
Shaffer and Trenham's (2002) study may suggest that the Central California tiger salamander consists of four populations, which are found in the Bay Area, Central Valley, southern San Joaquin Valley, and the Central Coast Range. Their genetic study suggests that levels of interchange among these populations are low, and that populations or groups of populations (metapopulations) are genetically different from one another (Shaffer and Trenham 2002). However, the geographic boundaries between some of these populations have not been fully delineated (e.g., Bay Area and Central Coast Range populations in the vicinity of the Contra Costa County/Alameda County lines, and the border between the Central Coast Range/Central Valley populations). Therefore, we believe it is not appropriate at this time to treat each of these four populations as a separate DPS. Instead, we treat these four populations as a single group, which is genetically and geographically distinct from the Sonoma County and Santa Barbara County groups.
The Central California tiger salamander is geographically isolated and separate from the Sonoma County DPS and the Santa Barbara County DPS, which are federally listed. The Sonoma County population is separated geographically from the closest Central California tiger salamander populations located in Contra Costa, Yolo, and Solano Counties by the Coast Range, Napa River, and the Carquinez Straits, a distance of about 72 km (45 mi). There are no known records of the California tiger salamander in the intervening areas (D. Warenycia, CDFG, pers. comm. 2002). The Santa Barbara County population is geographically separated from the Central California tiger salamander by the La Panza and Sierra Madre Ranges, and the Carrizo Plain, which extends into the Tremblor Range in eastern San Luis Obispo and western Kern Counties (Shaffer et al. 1993). Thus, the same conditions that establish geographic isolation of the Santa Barbara County California tiger salamander and the Sonoma County California tiger salamander from the Central California tiger salamander work correlatively to establish that the converse is also true. There is no evidence of natural interchange of individuals between the Sonoma County and Santa Barbara County populations with the Central California tiger salamander. The genetic work discussed above (Shaffer and Trenham 2002) also indicates that natural interchange is unlikely. Therefore, the best available genetic data (Shaffer and Trenham 2002) for California tiger salamanders indicate that the Central California tiger salamander is distinct from the Sonoma County and Santa Barbara County DPSs. Significance
Under our DPS policy, once we have determined that a population
segment is discrete, we consider its biological and ecological
significance to the larger taxon to which it belongs. This
consideration may include, but is not limited to, evidence of the
persistence of the discrete population segment in an ecological setting
that is unique for the taxon; evidence that loss of the population
segment would result in a significant gap in the range of the species;
evidence that the population segment represents the only surviving
natural occurrence of a taxon that may be more abundant elsewhere as an
introduced population outside its historic range; and evidence that the [[Page 28653]]
discrete population segment differs markedly from other populations of the species in its genetic characteristics. We have found substantial evidence that two of these significance factors are met by the population of the Central California tiger salamander.
The extinction of the Central California tiger salamander would likely result in the loss of a significant genetic entity and create a significant gap in the range of the species. Shaffer and Trenham's recent genetic work (2002) indicates that the Central California tiger salamander consists of four populations. As discussed above, the Central California tiger salamander differs genetically from the Sonoma County and Santa Barbara DPSs. This supports the hypothesis that no natural interchange of the Central California tiger salamander occurs with the Santa Barbara County or the Sonoma County DPSs. Loss of the Central California tiger salamander would also result in a significant gap in the range of the species.
We evaluated the Central California tiger salamander, addressing the two elements which our policy requires us to consider in deciding whether a vertebrate population may be recognized as a DPS and considered for listing under the Act. We propose that the Central California tiger salamander is discrete, as per our policy, because it is both genetically different and geographically separated from the Santa Barbara County and Sonoma County DPSs. We propose that the Central California tiger salamander is significant because the loss of species would result in a significant gap in the range. It would also constitute loss of a genetically divergent portion of the species. Because the population segment appears to meet both the discreteness and significance criteria of our DPS policy, we propose that the Central California tiger salamander constitutes a DPS that qualifies for consideration for listing.
We have already listed the Sonoma County DPS and Santa Barbara County DPS as endangered. We will be reviewing the relationship between the Central California tiger salamander, and the Sonoma County and Santa Barbara County DPSs as part of this proposed rulemaking. Summary of Factors Affecting the Species
Section 4 of the Act, and the regulations (50 CFR part 424) promulgated to implement the listing provisions of the Act, describe the procedures for adding species to the Federal list of Endangered and Threatened Wildlife and Plants. We may determine a species to be endangered or threatened on the basis of one or more of the five factors described in section 4(a)(1) of the Act. These factors, and their application to the Central California tiger salamander, are described below.
We have analyzed threats to the California tiger salamander
throughout the four populations using information from 608 California
tiger salamander sites identified in the CNDDB, of which 486 sites are
known to be extant (Service 2003). This database includes the
localities listed by Shaffer et al. (1993), Seymour and Westphal
(1994), LSA Associates, Inc. (1994), and numerous other biologists. At
each of these localities, at least one California tiger salamander
(adult, juvenile or larva) has been identified by a biologist. Upland
habitat types in the vicinity of these localities include annual
grassland (49 percent) and oak savannah (12 percent) (California GAP
1996; Service 2003). The remaining upland habitat types are
agricultural crops, urban areas, and other natural habitats. The
localities in the CNDDB for which one or more wetland type was
identified included vernal pools, artificial bermed ponds or
stockponds, or ponds. Threats are analyzed in detail below in the discussion of the five factors affecting the species.
A. The Present or Threatened Destruction, Modification, or Curtailment of Its Habitat or Range
Destruction, modification, and curtailment of Central California tiger salamander habitat is caused by a variety of urban and agricultural land uses. We define urban impacts to include a variety of nonagricultural development activities, such as building and maintenance of housing, commercial, and industrial developments; construction and widening of roads and highways; golf course construction and maintenance; trash dumping, landfill operation and expansion; operation of gravel mines and quarries; dam building; and inundation of habitat by reservoirs. Agricultural impacts include the conversion of native habitat by discing and deepripping; and cultivation, planting, and maintenance of row crops, orchards, and vineyards.
Many habitat changes began before California tiger salamanders were widely collected or studied by biologists. Habitat degradation or loss, alteration of vernal pools and seasonal ponds, introduction of nonnative organisms, and other changes have occurred throughout the range of this species (Shaffer et al. 1993; Jennings and Hayes 1994; Thelander 1994).
These impacts threaten both wetland breeding habitat and upland habitat. Even salamanders utilizing breeding sites that are protected from development may not persist as viable populations if upland sites are unavailable. Earthmoving operations and cultivation in upland habitat can directly or indirectly kill or injure California tiger salamanders in burrows or on the surface by crushing or trapping them. These practices can also expose salamanders to adverse environmental conditions (increased predation, high temperatures, low humidity) and alter surface hydrology (potentially affecting breeding ponds). Discing, deepripping, or grading of upland habitat also destroys California ground squirrel burrows and other crevices, making suitable upland sites unavailable and reducing longterm adult survival of Central California tiger salamanders. Ongoing agricultural and urban land uses prevent upland sites from being reestablished, and may kill or injure salamanders that enter the developed area. Existing vineyards and orchards can disrupt annual migration patterns and cut off access to breeding wetlands as salamanders avoid moving through areas with heavy canopy cover (S. Sweet, in litt. 1998). Agricultural and urban land uses can interfere with dispersal among breeding sites and prevent natural recolonization of ponds after local extirpation.
Filling, discing, or excavating wetland habitat can directly kill
or injure larvae, eggs, or breeding adults, and prevents future use of
the wetland for reproduction. Additionally, surviving adults may be
unable to locate alternative breeding sites in subsequent years.
Erosion from agriculture or grading can similarly impair reproductive
success by causing sedimentation and degradation of nearby wetlands (S.
Sweet, in litt. 1998; Sneed 2000). Changes in flooding duration and
depth caused by urban and agricultural land use (e.g., digging of
drainage/irrigation ditches, construction of permanent ponds or
reservoirs, deepening or berming of seasonal wetlands, redirection of
runoff from developments) can reduce reproductive success either by
prematurely drying wetlands and desiccating larvae, or by extending the
flooded period and facilitating invasion of exotic predators (see
Factor C). Other secondary effects of agricultural and urban land uses
include increased road mortality, drift and runoff of pesticides and fertilizers,
and ongoing rodentcontrol activities (see Factor E).
A comparison of the past and present extent of suitable habitat for the Central California tiger salamander indicates that the range of the species has been substantially reduced from its historical distribution. Historically, approximately 3.67 million hectares (ha) (9.06 million acres (ac)) of valley and coastal grasslands existed within the range of the Central California tiger salamander, with an additional 2.64 million ha (6.53 million ac) supporting an overstory of blue oak/foothill pine, valley oak, or mixed hardwoods (Kuchler 1988), for a total of 6.31 million ha (15.59 million ac) of potential habitat. However, urbanization and intensive agriculture have eliminated virtually all valley grassland and oak savanna habitat from the Central Valley floor. Valley grasslands and, consequently, Central California tiger salamanders are now distributed primarily in a ring around the Central Valley (Heady 1977). An analysis of CNNDB (2002) and Service (2003) records indicate that currently there are only about 4.5 million ha (11.1 million ac) of potential habitat where the California tiger salamander may still be extant. From 1995 to 2020, the human population in the range of the Central California tiger salamander (Central Valley, Bay Area, and Central Coast Counties) is projected to grow by 49 percent (from 12.8 million to 19.1 million people) (California Department of Water Resources (CDWR) 1998). Therefore, impacts on the Central California tiger salamander and conversion of its habitat resulting from urban development are expected to continue.
The relative loss of habitat has been even more extreme with respect to vernal pools, the historic breeding habitat of the Central California tiger salamander. Approximately 1.68 million ha (4.15 million ac) of grasslands in 20 Central Valley Counties are estimated to have supported vernal pools at the time of European settlement (Holland 1978, 1998a, 1998b; Holland and Jain 1988). Most of this area, excepting the northern Sacramento Valley, was within the Central California tiger salamander's historical range. The remaining vernal pool complexes are now fragmented and reduced in area. Where vernal pools remain, they are often disturbed and degraded by drainage modification, overgrazing, ORV use, nonnative plant invasion, trash dumping, road construction, and urban development (Jones and Stokes Associates 1987; 59 FR 48136; KeelerWolf et al. 1998). Vernal pools are now recognized as a threatened resource (Jones and Stokes Associates 1987; Wright 1991; 59 FR 48136). During the 1980s and 1990s, vernal pool grasslands continued to be lost at an estimated rate of 1.5 percent per year (Holland 1998a, 1998b). As of 1997, 377,165 ha (931,991 ac) of vernal pool grasslands remained in the Central Valley, representing a loss of approximately 78 percent (Holland 1998a, 1998b). Along the southeastern edge of the Central Valley, from San Joaquin to Fresno Counties, at least 25 percent of the 259ha (640ac) sections that had contained vernal pools in 1970 (Holland 1978) were wholly converted to agriculture or urban uses by 1994 (Seymour and Westphal 1994). This conversion estimate is probably conservative because it does not include partially converted sections where vernal pool habitat may also have been lost (Seymour and Westphal 1994).
Shaffer et al. (1993) detected California tiger salamanders in only 36 of 86 localities (42 percent) that had been previously recorded, and ponds currently occupied by California tiger salamanders were significantly higher in elevation than those that were unoccupied or had been previously occupied. These data suggest that lowelevation breeding sites on the valley floor have been eliminated in recent years, thereby restricting the species to higherelevation habitats on the margin of its ecological requirements (Shaffer et al. 1993; Seymour and Westphal 1994; Fisher and Shaffer 1996).
In both our final rule listing the Santa Barbara County DPS of the California tiger salamander (65 FR 57242), and the Sonoma County DPS of the California tiger salamander (67 FR 47726), we described land conversions to more intensive agriculture, especially conversions to grape vineyards, as being a factor in the species' decline. Data from the California Agricultural Statistics Service (CASS) (2002) provides further corroboration that this is a factor and shows that the phenomenon extends over much of the Central California tiger salamander's current and historic range.
Urban development poses a similar significant threat to the Central California tiger salamander. The human population of the State of California is continuing to increase, along with a concomitant increase in urban development. According to the 2000 census, the number of people in California has increased by 13.8 percent since 1990 (California Department of Finance 2002). The average growth in human population within the Counties in the range of the Central California tiger salamander has been 19.5 percent. Counties in the East Bay region and the Highway 99 corridor in the San Joaquin Valley are undergoing increases both in human population and related urbanization. Sub populations at fortyone records of the Central California tiger salamander from the CNDDB data base have been extirpated by urban development (Service 2003).
The information documenting the present or threatened destruction, modification, or curtailment of Central California tiger salamander habitat or range due to urbanization and other factors is organized below as it applies to four populations of the species (Shaffer et al. 1993; Shaffer and Trenham 2002) that we have not yet listed.
Bay Area Population (Alameda, Santa Clara, San Benito, southwestern San Joaquin, western Stanislaus, and western Merced Counties): Thirty two percent (194 of 608 sites) of the known California tiger salamander records are in this population, most of them in eastern Alameda and Santa Clara Counties (CNDDB 2002). Fortynine of these records in the Bay Area population are considered extirpated due to urbanization, orchards and vineyards, and hybridization with nonnative tiger salamanders (CNDDB 2002; Service 2003). There are 83,386 ha (206,051 ac) of potential habitat for the California tiger salamander in the Bay Area (Service 2003).
The East Bay area of the Bay Area and Livermore Valley area has undergone intensive urban development in recent years. The total human population of Santa Clara, Contra Costa, Alameda, Solano, and Yolo Counties increased by approximately 86 percent between 1990 and 2002. From 1995 to 2020, the human population is projected to increase by 18 percent for the San Francisco Bay hydrologic region, with agricultural crop land use projected to remain around 26,305 ha (65,000 ac) (CDWR 1998). From 1990 to 1996, 16,457 ha (40,665 ac) of native habitat were converted to urban and agricultural uses in Santa Clara, Alameda, and San Benito Counties (California Department of Conservation (CDC) 1994, 1998). Approximately 90 percent of land conversions in Santa Clara, Alameda, and Contra Costa Counties were to urban use.
Of 98 California tiger salamander localities where wetland type was
identified, only 15 percent (15) were located in vernal pools. These
wetland type localities within the Bay Area population of California
tiger salamanders occur within the SolanoColusa and Livermore vernal
pool regions (KeelerWolf et al. 1998). However, little vernal pool habitat
remains within these regions. Many of the SolanoColusa vernal pools have been destroyed or degraded by agricultural conversion, water impounding for waterfowl habitat enhancement, urban development, and roadbuilding. Most of the vernal pools in the Livermore Region have been destroyed or degraded by urban development, agriculture, water diversions, poor water quality, and longterm overgrazing (KeelerWolf et al. 1998). Many breeding sites in the Bay Area population are in artificial water bodies rather than natural vernal pools. Overall, 43 percent (83) of the records are in stock, farm, or berm ponds used for cattle grazing and as a temporary source of water for small farm irrigation (CNDDB 2002).
California tiger salamander localities in Contra Costa and Alameda Counties may be affected by ORV use; at least 10 proposed housing developments; 3 golf courses; infrastructure construction, including expansion of an airport, a landfill, and a power station; and highway construction (CNDDB 2002). These development projects may destroy upland habitat and wetland breeding habitat, killing salamanders and reducing the viability of populations at the affected localities.
In eastern Contra Costa and Alameda Counties, especially the Livermore and Amador Valleys, urban expansion continues at a rapid pace. California tiger salamander populations in the Livermore Valley are severely threatened by the ongoing conversion of 14,527 ha (35,897 ac) of grazing land to subdivisions and vineyards (Stebbins 1989; East Bay Regional Park District (EBRPD) 1999). Almost the entire valley floor, and large portions of the adjacent hills, are being developed or are being considered for development and eventual annexation. The North Livermore and South Livermore Valley Specific Plans represent 11,727 ha (28,977 ac) of planned urban development in and around Livermore Valley (EBRPD 1999). Urban Growth Boundaries encompass 108,262 ha (267,520 ac), including the Livermore, La Costa, Amador, Sunol, and Vallecitos valleys in east Alameda County and the Clayton, Lone Tree, Deer, and Briones valleys of eastern Contra Costa County (Alameda County Planning Department 1993; EBRPD 1999). These valleys constitute much of the core area inhabited by the Bay Area California tiger salamander population. Shaffer et al. (1993) found that the East Bay Counties of Alameda and Contra Costa supported the greatest concentrations of California tiger salamander. Three localities are known from near San Francisco Bay in southwestern Alameda County, and are partially protected by San Francisco Bay National Wildlife Refuge.
California tiger salamanders at a university in Palo Alto declined to near extirpation due, in part, to urban development of adjoining upland areas (Barry and Shaffer 1994), but water management and other takereduction efforts have been implemented in recent years to protect the population (Thomas Reid Associates 1998). A locality within the City of San Jose is threatened by urban development. Several areas in southern Santa Clara County also are undergoing urban expansion.
Central Valley Population (Yolo, Solano, Sacramento County south of the Cosumnes River, northeastern Contra Costa, eastern San Joaquin, western Amador, western Calaveras, western Tuolumne, eastern Stanislaus, Merced, western Mariposa, and northwestern Madera Counties): Fortyseven percent (286 of the 608 sites) of the known California tiger salamander records are in this population (CNDDB 2002). Subpopulations at 37 of recorded locations in the Central Valley Population are considered extirpated (CNDDB 2002; Service 2003). Urban development and agriculture have eliminated much of the grassland and vernal pools. From 1996 to 1998, 14,361 ha (35,487 ac) of native habitat were converted to urban and agricultural uses in Yolo, Solano, Contra Costa, Merced, Sacramento, San Joaquin, Stanislaus, and Madera Counties (CDC 2000). There are 146,600 ha (362,253 ac) of potential habitat for the California tiger salamander in the Central Valley (Service 2003). The species historically occurred as far north as Butte County but has not recently been documented north of the Cosumnes River. The remaining sites inhabited by the California tiger salamander occur in the lowelevation foothills on the eastern side of the Central Valley (Shaffer et al. 1993).
Of 127 California tiger salamander localities where wetland type was identified, 26 percent (33) were in vernal pools. These wetland type localities within the Central Valley population of California tiger salamanders occurs within the southeastern Sacramento Valley and southern Sierra foothills vernal pool regions (KeelerWolf et al. 1998). Vernal pools in both regions are threatened by conversion of grasslands and grazing land to housing developments and intensive agriculture (see Factor E).
California tiger salamander localities in the Central Valley population may be affected by recently implemented development projects, including vineyards and proposed highway construction. These development projects may destroy upland habitat and wetland breeding habitat, killing salamanders and reducing the viability of populations at the affected localities. Large vineyards planted in areas along the San JoaquinSacramento County line have degraded and destroyed habitat for California tiger salamanders.
In Yolo and Solano Counties, the major impacts to California tiger salamander populations have been agricultural. Portions of the California tiger salamander locality at Jepson Prairie in Solano County is protected by the University of California Natural Reserve System and the Solano Land Trust. However, some upland habitat may have been disrupted by construction of a natural gas pipeline in the vicinity. California tiger salamanders also were found at some proposed power plant sites near Jepson Prairie.
In Stanislaus County, California tiger salamanders were considered extirpated until they recently were found by biologists surveying a potential route for a highway bypass near Oakdale (California Department of Transportation 2000). This highway route threatens the only known population of California tiger salamanders in the Oakdale area. However, other populations are known to exist within Stanislaus County outside the Oakdale area.
South San Joaquin Population: (western Madera, central Fresno, and northwestern Tulare Counties north of the St. Johns and Kaweah Rivers): Nine percent (56 of the 608 sites) of the known California tiger salamander sites are in this population (CNDDB 2002). However, 18 of these sites in the South San Joaquin population are considered extirpated (CNDDB 2002; Service 2003). From 1996 to 1998, 4,509 ha (11,142 ac) of native habitat were converted to urban and agricultural uses in Fresno, Tulare, and Madera Counties (CDC 2000). There are 24,450 ha (60,418 ac) of potential habitat for the California tiger salamander in the southern San Joaquin Valley (Service 2003).
Ninetyseven percent (31) of 32 localities for which wetland type
was identified in the South San Joaquin population are within vernal
pools. These wetland type localities within the South San Joaquin
population of the California tiger salamander occur within the southern
Sierra Foothill Vernal Pool Region (KeelerWolf 1998). Although we are
unaware of a specific quantified estimate of loss for this vernal pool region, we believe that a significant
number of vernal pools in this region have been destroyed, fragmented, and degraded by conversion to intensive agriculture and housing developments.
Shaffer et al. (1993) were unable to find breeding habitat to sample for presence of the California tiger salamander over most of the original grassland habitat of the San Joaquin Valley. Where ponds were located, California tiger salamanders generally were absent (72 percent of 324 ponds sampled were absent). The rarity of this species in the San Joaquin Valley, in habitat that was apparently suitable historically, suggests widespread extirpation of California tiger salamanders from habitat conversion to agricultural and urban uses (Stebbins 1989). Large areas of California tiger salamander habitat were destroyed and degraded by major urbanization in this region during the 1970s and 1980s (Shaffer et al. 1993). Agricultural, housing, road, and commercial developments on the valley floor of Fresno, Madera, and Tulare Counties have reduced suitable habitat to a fraction of the species' historical range (J. Halstead, Kings River Conservation District, in litt. 1994). Most remaining salamander habitat on the eastern side of the Central Valley occurs on tracts of privatelyowned ranch land (Seymour and Westphal 1994).
California tiger salamander localities in the South San Joaquin population may be affected by proposed development projects, including housing developments and highway construction. These development projects would likely destroy upland habitat and wetland breeding habitat, likely killing salamanders and reducing the viability of populations at the affected localities.
Several large water storage and delivery projects have been constructed in the South San Joaquin population. These projects have flooded large areas of known and potential salamander habitat. Additional habitat has been lost to construction from associated State and County park recreational facilities (e.g., boat ramps, campgrounds, parking lots) and agriculture and urbanization facilitated by water supply development.
Numerous new housing developments and golf courses are planned or in progress around Millerton Lake in Fresno and Madera Counties (J. Halstead, in litt. 1994; The Keith Companies 1994). Extensive areas of upland habitat and wetland breeding habitat will likely be destroyed by these developments, potentially killing many salamanders and/or further reducing the viability of any remaining habitat at these localities.
California tiger salamanders are known from eight localities in Tulare County, most of which are surrounded by a matrix of agricultural lands.
Central Coast Population (southern Santa Cruz, Monterey, extreme western San Benito, extreme western Fresno, extreme western Kings, extreme northwestern Kern, and San Luis Obispo Counties): Twelve percent (72 of the 608 localities) of the known California tiger salamander records are in the Central Coast Range population. Nineteen of these sites in the Central Coast population are considered extirpated (CNDDB 2002; Service 2003). From 1996 to 1998, 2,084 ha (5,149 ac) of native habitat were converted to urban and agricultural uses in San Luis Obispo and Monterey Counties (CDC 2000). There are 28,411 ha (70,205 ac) of potential habitat for the California tiger salamander in the Central Coast.
California tiger salamanders in this population occurred predominantly in stock ponds, reservoirs, seasonal lakes, and intermittent streams. Of the California tiger salamander localities in this population where the wetland type was identified, 26 percent (86) were vernal pools. The wetland type localities within the Central Coast Range population of the California tiger salamander occur in the Central Coast and San Joaquin Valley Vernal Pool Regions (KeelerWolf et al. 1998). The annual loss of vernal pools from 1994 to 2000 in Monterey, San Benito, San Luis Obispo, Santa Barbara, and Ventura Counties appears to be accelerating to a rate of 2 to 3 percent annually (Holland 2003).
Two California tiger salamander localities occur at a 8,064 ha
(19,927 ac) development project site that comprises 14 percent of the
Greater Monterey Peninsula Planning Area, which is nearly half of the
Planning Area's unimproved land. Construction on this project has been
initiated (D. Steeck, Service, pers. comm. 2000). Eleven localities
occur on Fort Ord, an 11,220 ha (27,726 ac) former military
installation that has been transferred to the U.S. Bureau of Land
Management (BLM), California Department of Parks and Recreation,
California State University, Santa Cruz, and Monterey County
municipalities. The proposed habitat management plan (Jones and Stokes
Associates 1993) for Fort Ord includes protection of salamander
breeding habitat at seven of these localities within the designated
Natural Resource Management Area (NRMA) managed by BLM. Two of the
localities in the NRMA are within a highway easement, and may be
imperiled due to future road construction. The protected area has
historically been extensively used by ORVs, but recent enforcement of
ORV restrictions by BLM has apparently reduced this problem (R. Lewis,
BLM, pers. comm. 1999). Excavation for removal of unexploded ordnance
could potentially disrupt breeding or upland habitat in the NRMA (Jones
and Stokes Associates 1993), but ordnance removal in breeding ponds has
not yet been deemed necessary (D. Steeck, pers. comm. 2000). The
remaining four localities on Fort Ord are projected for development as
recreational areas, commercial centers, and a university campus.
Development in these areas may avoid breeding ponds, but additional upland habitat is likely to be lost and fragmented.
B. Overutilization for Commercial, Recreational, Scientific, or Educational Purposes
There is no evidence that overutilization is a factor causing decline of the California tiger salamander.
C. Disease or Predation
Relatively little is known about the diseases of wild amphibians (Alford and Richards 1999). The specific effects of disease on the Central California tiger salamander are not known and the risks to the animal have not been determined.
Pathogen outbreaks have not been documented in the Central California tiger salamander. Nevertheless, disease must be considered a potential future population threat because of the relatively small, fragmented remaining Central California tiger salamander breeding sites, the many stresses on these sites due to habitat losses and alterations, and the many other potential diseaseenhancing anthropogenic changes which have occurred both inside and outside the species' range.
A number of nonnative California species have likely adversely
affected the Central California tiger salamander in many parts of its
range through predation and competition. Bullfrogs prey on California
tiger salamanders (P. Anderson 1968; Lawler et al. 1999). The bullfrog,
native to the United States east of the Great Plains, was introduced
into California in the late 1800s and early 1900s, and it rapidly
spread throughout the State (Storer 1925 as cited in Moyle 1973; Hayes
and Jennings 1986). Morey and Guinn (1992) documented a shift in [[Page 28657]]
amphibian community composition at a vernal pool complex, with salamanders becoming proportionally less abundant as bullfrogs increased in number. Although bullfrogs are unable to establish permanent breeding populations in unaltered vernal pools and seasonal ponds because they require more than 1 year to complete their larval stage, dispersing immature bullfrogs take up residence in such water bodies during winter and spring where they prey on native amphibians, including larval salamanders (Morey and Guinn 1992; Seymour and Westphal 1994). A strong negative correlation exists between bullfrog presence and California tiger salamander presence (Shaffer et al. 1993; Seymour and Westphal 1994).
Because bullfrogs are known to travel at least 2.6 km (1.6 mi) from one pond to another (Bury and Whelan 1984), they have the potential to naturally colonize new areas where they do not currently exist, including where Central California tiger salamanders occur. In one study of the eastern San Joaquin Valley, it was found that 22 of 23 ponds (96 percent) with California tiger salamanders were within the bullfrogs' potential dispersal range (Seymour and Westphal 1994). In addition, because bullfrogs are still sought within California for sport and as food, and may be taken wit
FOR FURTHER INFORMATION CONTACT
Sacramento Fish and Wildlife Office, at the address listed above (telephone 916/4146600; facsimile 916/414 6713).