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Endangered and Threatened Wildlife and Plants: 90-day Finding on a Petition To List the Yosemite Toad as Endangered

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Fish and Wildlife Service, Interior.


Notice of 90-day petition finding.


The U.S. Fish and Wildlife Service (Service) announces a 90-day finding on a petition to list the Yosemite toad (Bufo canorus) as endangered under the Endangered Species Act (Act) of 1973, as amended (16 U.S.C. 1531 et seq.). We find that the petition presents substantial scientific or commercial information to indicate that listing the species may be warranted. Therefore, we are initiating a status review to determine if the petition action is warranted. To ensure that the review is comprehensive, we are asking for information and data regarding this species.


The finding announced in this document was made on October 5, 2000. To be considered in the 12-month finding for this petition, comments and information should be submitted to the Service by December 11, 2000.


Data, information, comments, or questions concerning this petition should be submitted to the Field Supervisor; Sacramento Fish and Wildlife Office; Sacramento Fish and Wildlife Office; 2800 Cottage Way, Room W-2065; Sacramento, California 95825. The petition finding, supporting data and comments are available for public inspection, by appointment, during normal business hours at the above address.

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Jason Davis or Maria Boroja at the Sacramento Fish and Wildlife Office (see ADDRESSES section above), or at (916-414-6600.

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Section 4(b)(3)(A) of the Endangered Species Act (Act) of 1973, as amended (16 U.S.C. 1531 et seq.), requires that the Service make a finding on whether a petition to list, delist, or reclassify a species presents substantial information indicating that the petitioned action may be warranted. To the maximum extent practicable, this finding is to be made within 90 days of the receipt of the petition, and the finding is to be published promptly in the Federal Register. If the finding is that substantial information was presented, the Service will commence a review of the status of the involved species. This finding is based on information contained in the petition, supporting information submitted with the petition, and other information available to the Service at the time the finding was made.

The processing of this petition conforms with the Service's final listing priority guidance published in the Federal Register on October 22, 1999 (64 FR 57114). The guidance clarifies the order in which we will process rulemakings. Highest priority is processing emergency listing rules for any species determined to face a significant and imminent risk to well-being (Priority 1). Second priority (Priority 2) is processing final determinations on proposed additions to the lists of endangered and threatened wildlife and plants. Third priority (Priority 3) is processing new proposals to add species to the lists. The processing of administrative petition findings (petitions filed under section 4 of the Act) is the fourth priority (Priority 4). The processing of critical habitat determinations (prudency and determinability decisions) and proposed or final designations of critical habitat will be funded separately from other section 4 listing actions and will no longer be subject to prioritization under the listing priority guidance. The processing of this petition finding is a Priority 4 action.

We have made a 90-day finding on a petition to the list Yosemite toad (Bufo canorus) as an endangered species. On Monday, April 3, 2000, we received a Start Printed Page 60608petition, dated February 28, 2000, to list the Yosemite toad as endangered. The petition was submitted by the Center for Biological Diversity and Pacific Rivers Council. The letter clearly identified itself as a petition and contained the names, signatures, and addresses of the petitioners. Included in the petition was supporting information relating to the species' taxonomy and ecology, adequacy of existing regulatory mechanisms for the species, and the historic and present distribution, current status, and potential cause of decline. This notice constitutes the 90-day finding for the February 28, 2000, petition.

The Yosemite toad is a high elevation species that occurs in the central Sierra Nevada Mountains of California (Stebbins 1985). The range of the Yosemite toad extends from Ebbetts Pass, Alphine County, to south of Kaiser Pass and Evolution Lake, Fresno County (Stebbins 1966, Karlstrom 1962, 1973). According to the petition, the Yosemite toad commonly occurs at elevation between 2,438 and 3.047 meters (8,000 and 10,000 feet), with an overall elevation range of 1,950 to 3,500 meters (6,400 to 11,300 feet).

The Yosemite toad is a member of the Boreas-canorus group, the most primitive of three evolutionary lines of North American Bufo (Camp 1917, Karlstrom 1962). According to Camp (1916), the Yosemite toad has long been recognized as a distinct species. The Yosemite toad is a close relative of three toad species, the western toad (Bufo boreas), black toad (Bufo exsul), and Amargosa toad (Bufo nelsoni) (Blair 1972, Stebbins 1985). The petitioners state that Yosemite/western toad hybridization occurs in the northern portion of the Yosemite toad's range in the Blue Lake region of the Carson-Iceberg Wilderness, just southeast of Carson Pass in Alphine County (Karlstrom 1973, Stebbins 1966).

The petition and accompanying documentation state that the species qualifies for listing pursuant to the Act due to potential habitat destruction and modification, the presence of disease in combination with natural predation, the inadequacy of existing regulatory mechanisms, and other natural or human-caused factors affecting its continued existence. The petitioners contend that natural and human-induced changes to Yosemite toad habitats, including (1) livestock grazing, (2) contaminant introductions, (3) non-native fish introductions, (4) disease (5) ultraviolet radiation, (6) climate change, (7) acid deposition, (8) drought, and (9) other factors, separately and in combination, are responsible for the range-wide decline of the species.

There have been few if any studies to date on the direct effect of contaminant introductions on Yosemite toad populations. However, several studies show that significant levels of contaminants have been deposited in high Sierran aquatic ecosystems from pesticide drift, acid precipitation, and smog drift (Seiber et al. 1998, Aston and Seiber 1997, Cahill et al. 1996, Miller 1996, Byron 1991, Nikolaidis 1991, Laird et al. 1986). The petitioners believe that contaminant introductions can harm toad populations through lethal and sublethal effects including delayed metamorphosis, reduced breeding and feeding activity (Berrill et al. 1993, 1994, 1995,1998, Boyer and Grue 1995, Beaties and Tyler-Jones 1992, Corn and Vertucci 1992, Hall and Henry 1992). In addition, contaminant introduction may weaken the immune systems of toads rendering them more susceptible to disease such as chytrid fungus and red-legged disease (Aeromonas hydrophila) (Carey et al. 1993, 1995, 1999, Jennings 1996, Drost and Fellers 1996, Sherman and Morton 1993).

There is ample evidence to suggest that Yosemite toads cannot coexist with introduced fish. In addition, there are strong indications that nonnative fish introductions have contributed to the decline of the toad. Not only do nonnative fish prey upon adult, juvenile and larval toads, they also alter the food chain of high Sierran aquatic ecosystems (Knapp 1996, Jennings 1996, Bradford 1989, 1993). The petitioners state that the most significant effect of nonnative fish on Yosemite toads is that they preclude the use of the deeper and more permanent water bodies that provide refuge for toads during periods of prolonged drought. The loss of higher quality, permanent breeding habitats for Yosemite toads disrupts their ability to recolonize peripheral areas after long periods of drought, and renders them more susceptible to localized extinctions (Knapp 1996, Drost and Fellers 1994, 1996, Bradford et al. 1993).

The petitioners state that disease likely plays a significant role in the widespread decline of Yosemite toad populations. Two diseases that may affect Yosemite toads are red-legged disease, which is caused by a freshwater bacteria, and chytrid fungus. Sherman and Morton (1984, 1993) noted the mortality of adult Yosemite toads due to red-legged disease at Tioga Pass during the 1970's. Chytrid fungus, an aquatic pathogen discovered after 1993, has caused mortality in many amphibian species in the United States and worldwide. An investigation of museum specimens of Yosemite toads collected by Sherman and Morton at Tioga Pass during a die-off in 1977-1978 found those toads to be infected with chytrid fungus (Carey et al. 1999). The petitioners state that there is significant information yet to be discovered regarding aquatic pathogens and their relationship to the ecology of Yosemite toads. Should evidence indicate that Yosemite toads have evolved with aquatic pathogens, then other stressors including contaminant introductions and UV-radiation may be reducing the ability of toads to fight off infection from these pathogens (Sherman and Norton 1993, Drost and Fellers 1996, Carey et al. 1993, 1995, 1999, Jennings 1996, Taylor et al. 1999).

The petitioners state that there are other natural and anthropogenic factors that may be negatively affecting the Yosemite toad, including (1) airborne contamination, (2) ultraviolet radiation, and (3) climate change. However, there are significant gaps in the extent of the information regarding affects of airborne contaminants on Yosemite toads. The affect of UV-radiation and global warming on Yosemite toad populations is also lacking at this time. These factors may provide additional stresses on toad populations that are already being assaulted by nonnative fish, livestock grazing, drought, and disease. Combinations of stresses may explain the significant declines of Yosemite toads recorded over the past few decades.

Several studies and observations made within the first half of the twentieth century report that Yosemite toads were abundant throughout their range, especially within Yosemite National Park (Grinnell and Storer 1924, Karlstrom 1962, Mullally 1953, Mullally and Cunningham 1956, Yosemite National Park Office 1999). More recent studies indicated that Yosemite toads have suffered significant declines in both abundance and distribution throughout their range. Jennings and Hayes (1994) reported that, even though Yosemite toads occur in areas that are free from physical disturbance, the species has declined or disappeared from 50 percent of known historic sites.

Within Yosemite National Park, the heart of the Yosemite toad's range, there are several documented declines in the distribution and abundance of Yosemite toad populations. Drost and Fellers (1994, 1996) resurveyed areas within the park that were originally surveyed in the first quarter of last century by the U.C. Berkeley survey team lead by Grinnell and Storer. By the 1990s, Yosemite toads only occupied 50 Start Printed Page 60609percent of these sites. The petitioners note that in a subsequent amphibian survey within Yosemite National Park, Fellers (1997) found 5 locations occupied by Yosemite toads out of 260 survey sites. The petitioners do not report whether these 260 survey locations were historically occupied by Yosemite toads. Additionally, several other sites that once supported abundant Yosemite toad populations including Tioga Pass, Sylvester Meadows, and several nearby sites have shown complete disappearances of toads in recent years (Karlstrom 1962, Sherman and Morton 1993). Sherman and Morton (1993) further documented significant declines in toad populations at their Tioga Pass Meadow study area. They counted an average of 257 toads annually during the period of 1974-1978 at Tioga Pass Meadow. By 1982, toad populations had declined to 28 individuals and in 1990, only one female, two males, and 4 to 6 egg masses. In 1991, these researchers noted only two egg masses and a single calling male. Other researchers have corroborated this decline (Drost and Fellers 1994). Additional population declines of Yosemite toads were observed at Saddlebag Lake, Frog Lake, Hoover Lake, and Mildred Lake (Sherman and Morton 1993).

The trend of populations declines also holds true for sites outside of Yosemite National Park. Bradford and Gordon (1992) conducted a survey of 235 randomly selected sites in potential Yosemite toad habitat above 2,625 meters (8,000 feet) and found only 17 sites occupied. In addition, the petitioners cite a survey conducted by David Martin (1990) that found of 75 historic localities surveyed throughout the high Sierra, only 40 were occupied. During his survey, Martin (1990) found no toads at historic locations at elevations below 2,461 meters (7,500 feet). Furthermore, Martin (1990) reported that of the 40 sites with toads present, he found an average of 5.75 individuals. The petition cites a personal communication with David Martin (San Jose State University, pers. comm. 2000), indicating that historically, Yosemite toad numbers were estimated to be over 100 individuals per site at each of these 75 locations. Additional toad declines have been reported by Martin (1992) at Emigrant Meadow and Lunch Meadow in the Emigrant Wilderness, Stanislaus National Forest, and around Sonora Pass, where toad populations that had once been abundant are now small or undetectable. This trend appears to hold for toad populations on the El Dorado and Sequoia National Forests (Stebbins 1966).

We have reviewed the petition and other information available in our files. Based upon this review, we believe that substantial evidence exists that listing of this species as endangered may be warranted. When we make a positive finding, we also are required to promptly commence a review of the status of the species. Based upon available and any newly obtained information, we will issue a 12-month finding as required by section 4(b)(3)(B) of the Act. Petitioners also requested that critical habitat be designated for the Yosemite toad; the 12-month finding will address this issue.

Public Information Requested

The Service hereby announces its formal review of the species' status pursuant to this 90-day petition finding. We request any additional data, comments, and suggestions from the public, other concerned government agencies, the scientific community, industry, or any other interested parties concerning the status of the Yosemite toad. Of particular interest is information regarding: (1) The existence and status of additional populations, (2) the implementation of any actions that are benefitting the species, and (3) the impact of livestock grazing, contaminant introductions, non-native fish introductions, disease, ultraviolet radiation, climate change, drought, and other factors that may be responsible for the range-wide decline of the species.

If you wish to comment, you may submit your comments and materials concerning this finding to the Field Supervisor, Sacramento Fish and Wildlife Office (see ADDRESSES section). Our practice is to make comments, including names and home addresses of respondents, available for public review during regular business hours. Respondents may request that we withhold their home address, which we will honor to the extent allowable by law. There also may be circumstances in which we would withhold a respondent's identity, as allowable by law. If you wish us to withhold your name and/or address, you must state this request prominently at the beginning of your comment. However, we will not consider anonymous comments. To the extent consistent with applicable law, we will make all submissions from organizations or businesses, and from individuals identifying themselves as representatives or officials of organizations or businesses, available for public inspection in their entirety. Comments and materials received will be available for public inspection, by appointment, during normal business hours at the above address.

References Cited

You may request a complete list of all references we cited, as well as others, from the Sacramento Fish and Wildlife Office (see ADDRESSES section).

Author: The primary author of this document is Jason Davis, Sacramento Fish and Wildlife Office (see ADDRESSES section).


The authority for this action is the Endangered Species Act of 1973, as amended (16 U.S.C. 1531 et seq.).

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Dated: October 5, 2000.

Jamie Rappaport Clark,

Director, Fish and Wildlife Service.

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[FR Doc. 00-26180 Filed 10-11-00; 8:45 am]