Endangered and Threatened Wildlife and Plants; 12-Month Finding on a Petition to List the Tucson Shovel-Nosed Snake (Chionactis occipitalis klauberi, 16050-16065 [2010-7133]

Agencies

• Fish and Wildlife Service
• DEPARTMENT OF THE INTERIOR

[Federal Register Volume 75, Number 61 (Wednesday, March 31, 2010)]
[Proposed Rules]
[Pages 16050-16065]
From the Federal Register Online via the Government Printing Office [www.gpo.gov]
[FR Doc No: 2010-7133]



[[Page 16050]]

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DEPARTMENT OF THE INTERIOR

Fish and Wildlife Service

50 CFR Part 17

[Docket No. FWS-R2-ES-2009-0070]
[MO 92210-0-0008-B2]


Endangered and Threatened Wildlife and Plants; 12-Month Finding 
on a Petition to List the Tucson Shovel-Nosed Snake (Chionactis 
occipitalis klauberi) as Threatened or Endangered with Critical Habitat

AGENCY: Fish and Wildlife Service, Interior.

ACTION: Notice of 12-month petition finding.

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SUMMARY: We, the U.S. Fish and Wildlife Service (Service), announce a 
12-month finding on a petition to list the Tucson shovel-nosed snake 
(Chionactis occipitalis klauberi) as threatened or endangered with 
critical habitat under the Endangered Species Act of 1973, as amended 
(Act). After review of the best scientific and commercial information 
available, we find that listing the Tucson shovel-nosed snake as 
threatened or endangered throughout its range is warranted. Currently, 
however, listing the Tucson shovel-nosed snake is precluded by higher 
priority actions to amend the Lists of Endangered and Threatened 
Wildlife and Plants. Upon publication of this 12-month petition 
finding, we will add the Tucson shovel-nosed snake to our candidate 
species list. We will develop a proposed rule to list the Tucson 
shovel-nosed snake as our priorities allow. We will make any 
determination on critical habitat during development of the proposed 
rule.

DATES: The finding announced in this document was made on March 31, 
2010.

ADDRESSES: This finding is available on the Internet at https://www.regulations.gov at Docket Number FWS-R2-ES-2009-0070. Supporting 
documentation we used in preparing this finding is available for public 
inspection, by appointment, during normal business hours by contacting 
the U.S. Fish and Wildlife Service, Arizona Ecological Services Office, 
2321 West Royal Palm Road, Suite 103, Phoenix, AZ 85021-4951. Please 
submit any new information, comments, or questions concerning this 
finding to the above address.

FOR FURTHER INFORMATION CONTACT: Steve Spangle, Field Supervisor, 
Arizona Ecological Services Office (see ADDRESSES) (telephone 602-242-
0210; facsimile 602-242-2513). If you use a telecommunications device 
for the deaf (TDD), please call the Federal Information Relay Service 
(FIRS) at 800-877-8339.

SUPPLEMENTARY INFORMATION:

Background

    Section 4(b)(3)(B) of the Endangered Species Act of 1973, as 
amended (Act) (16 U.S.C. 1531 et seq.), requires that, for any petition 
containing substantial scientific or commercial information indicating 
that listing the species may be warranted, we make a finding within 12 
months of the date of receipt of the petition. In this finding we 
determine that the petitioned action is: (a) Not warranted, (b) 
warranted, or (c) warranted, but immediate proposal of a regulation 
implementing the petitioned action is precluded by other pending 
proposals to determine whether species are threatened or endangered, 
and expeditious progress is being made to add or remove qualified 
species from the Lists of Endangered and Threatened Wildlife and 
Plants. Section 4(b)(3)(C) of the Act requires that we treat a petition 
for which the requested action is found to be warranted but precluded 
as though resubmitted on the date of such finding, that is, requiring a 
subsequent finding to be made within 12 months. We must publish these 
12-month findings in the Federal Register.

Previous Federal Actions

    We received a petition, dated December 15, 2004, from the Center 
for Biological Diversity requesting that we list the Tucson shovel-
nosed snake as threatened or endangered throughout its range and 
designate critical habitat within its range in the United States. The 
petition, which was clearly identified as such, contained detailed 
information on the natural history, biology, current status, and 
distribution of the Tucson shovel-nosed snake. It also contained 
information on what the petitioner reported as potential threats to the 
subspecies from urban development, agricultural practices, collecting, 
inadequacy of existing regulations, drought, and climate change. In 
response to the petitioner's requests, we sent a letter to the 
petitioner, dated September 7, 2005, explaining that, due to funding 
constraints in fiscal year 2005, we would not be able to address the 
petition in a timely manner. On February 28, 2006, the petitioner filed 
a 60-day notice of intent to sue (NOI) the Department of the Interior 
for failure to issue 90-day and 12-month findings, and a proposed 
listing rule, as appropriate, in response to the petition as required 
by 16 U.S.C. 1533(b)(3)(A) and (B). In response to the NOI, we agreed 
to submit a 90-day finding to the Federal Register as expeditiously as 
possible.
    On July 29, 2008, we made our 90-day finding that the petition 
presented substantial scientific information indicating that listing 
the Tucson shovel-nosed snake (Chionactis occipitalis klauberi) may be 
warranted. The finding and our initiation of a status review was 
published in the Federal Register on July 29, 2008 (73 FR 43905).
    This notice constitutes the 12-month finding on the December 15, 
2004, petition to list the Tucson shovel-nosed snake as threatened or 
endangered.

Species Information

Species Description

    The Tucson shovel-nosed snake is a small snake (250-425 millimeters 
(mm) (9.84-16.73 inches (in) total length) in the family Colubridae, 
with a shovel-shaped snout, an inset lower jaw, and coloring that 
mimics coral snakes (Mahrdt et al. 2001, p. 731.1). The most notable 
features of the Tucson shovel-nosed snake distinguishing it from the 
other subspecies are (a) the red crossbands suffused with dark pigment, 
making them appear brown or partly black, and (b) both black and red 
crossbands not encircling the body (Center for Biological Diversity 
2004, p. 2).

Taxonomy

    In considering taxonomic data, the Service relies ``on standard 
taxonomic distinctions and the biological expertise of the Department 
and the scientific community concerning the relevant taxonomic group'' 
(50 CFR Sec. 424.11(a)) and ``on the basis of the best scientific and 
commercial information'' (50 CFR Sec. 424.11(b)). The Service, not any 
professional organization or expert, bears the responsibility for 
deciding what taxonomic entities are to be protected under the Act. We 
address any conflicting information or expert opinion by carefully 
evaluating the underlying scientific information and weighing its 
reliability and adequacy according to the considerations of the Act and 
our associated policies and procedures and using the best scientific 
information available.
    Taxonomic nomenclature for the Tucson shovel-nosed snake has 
changed over time. The snake was first described as a subspecies, 
Sonora occipitalis klauberi, by Stickel in 1941 (p. 138). The genus was 
changed to Chionactis two years later (Stickel 1943, pp. 122-123). 
Since being described, the Tucson shovel-nosed snake has been widely

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accepted as a subspecies (Klauber 1951, p. 187; Stebbins 2003, p. 394; 
Crother 2008a, p. 48; Collins and Taggart 2009, p. 28), and is one of 
four currently recognized subspecies of the Western shovel-nosed snake, 
Chionactis occipitalis (Crother 2008a, p. 48; Collins and Taggart 2009, 
p. 28).
    In our 90-day finding for this petition (73 FR 43905), we 
determined that a recent study of genetic variation of mitochondrial 
DNA (Wood et al. 2006, hereafter Wood et al. 2008) found significant 
geographical structuring suggesting two distinct subspecies of Western 
shovel-nosed snake rather than four, combining western populations of 
Chionactis occipitalis occipitalis, the Mojave shovel-nosed snake, with 
Chionactis occipitalis talpina, the Nevada shovel-nosed snake; and 
southeastern populations of C. o. occipitalis with Chionactis 
occipitalis annulata, the Colorado Desert shovel-nosed snake, and C. o. 
klauberi. However, this study's inference was based on a single genetic 
marker of mitochondrial DNA and did not include examination of nuclear 
markers, which would more fully elucidate our understanding of the 
taxonomic standing of this subspecies. Therefore, in our 90-day 
finding, we continued to accept the currently recognized arrangement of 
subspecies, which includes C. o. klauberi (Mardt et al. 2001).
    Additionally, the petition requested that the Service consider an 
``intergrade zone'' between the Tucson shovel-nosed snake and the 
Colorado Desert shovel-nosed snake as part of the Tucson shovel-nosed 
snake's range. An intergrade zone is an area of overlap between the 
ranges of two subspecies where individuals may possess intermediate 
characters (attributes or features that distinguish a subspecies, such 
as coloration) or traits of both subspecies. It is generally recognized 
and accepted by practitioners of subspecies taxonomy that intergrade 
zones may exist between the ranges of two subspecies where the 
diagnostic characters of both subspecies may be found (Mayr 1942, p. 
107; Huxley 1943, p. 210-211; Mayr 1963, p. 368; Mayr 1969, pp. 193-
196; Mayr 1970, pp. 219-226; Wake 1997, pp. 7761-7762; Rodriguez-Robles 
and De Jesus-Escobar 2000, p. 42; Isaac et al. 2004, p. 465; Krysko and 
Judd 2006, p. 18; Wake 2006, p. 12). Current practice in the scientific 
literature is to objectively describe the ranges of different 
subspecies and any intergrade zones between them with narrative 
descriptions, maps, or both (e.g., Wake 1997, pp. 7761-7767; Rodriguez-
Robles and De Jesus-Escobar 2000, Fig. 1; Mahrdt et al. 2001, p. 731.2; 
Leache and Reeder 2002, p. 202; Krysko and Judd 2006, p. 18; Wake 2006, 
p. 11). Following this practice, intergrade zones are identified, but 
not assigned to either of the subspecies. As such, we find that 
including all shovel-nosed snakes within the intergrade zone into the 
subspecies taxon of the Tucson shovel-nosed snake would not be 
consistent with current scientific practice in describing the ranges of 
subspecies and the intergrade zone between them, and, therefore, we do 
not consider shovel-nosed snakes within the intergrade zone to be 
members of the Tucson shovel-nosed snake subspecies.
    In order to be compliant with 50 CFR 424.11(a) and to understand 
the taxonomic entity to consider for listing, the Service requested 
review and input on the issue of taxonomic classification and 
distribution of the Tucson shovel-nosed snake from nine individuals 
with biological and taxonomic expertise and background in this issue. 
Of the nine, six provided comments and input on specific questions we 
asked regarding the issue of determining species and subspecies, 
taxonomic classification, and geographical ranges (including the 
location of the boundary between the Tucson shovel-nosed snake and the 
intergrade zone) based on recent and historical studies and 
publications related to Tucson shovel-nosed snake taxonomic 
classification.
    We considered publications by Collins and Taggart (2009), Crother 
(2008a), Wood et al. (2008), Rosen (2003), Mahrdt et al. (2001), 
Klauber (1951), and the input from our solicited review by current 
experts in the field (four herpetological taxonomists and two C. 
occipitalis experts). The four herpetological taxonomists believed 
that, based on the most recent genetic work by Wood et al. (2008) using 
mitochondrial DNA, the subspecies C. o. klauberi does not warrant 
taxonomic recognition (Boundy 2008, p. 2; Burbrink 2008, p. 2; Crother 
2008b, p. 2; Frost 2008, p. 2). They suggested, based on Wood et al. 
(2008), that two lineages of C. occipitalis exist in the northwestern 
and southeastern portions of the species' range, which are not 
consistent with the current subspecies designations and their current 
ranges. Three of the taxonomists, plus one of the species experts, 
suggested additional studies using nuclear DNA markers or 
microsatellites (numerous short segments of DNA that are distributed 
throughout the genetic material of an organism) were needed to 
determine if C. o. klauberi is distinct, and if so, where the 
boundaries of its range are actually located (Boundy 2008, p. 3; 
Burbrink 2008, p. 2; Crother 2008b, p. 3; Holm 2008, p. 2).
    The two species experts believed that there is some agreement 
between morphological and mitochondrial DNA data, and supported 
acknowledging C. o. klauberi as a unique taxonomic entity (Holm 2008, 
p. 1; Rosen 2008a, pp. 6-12). One of the experts suggested a range 
similar to the one that is currently recognized for klauberi (Holm 
2008, p. 5) and the other, although recommending retaining the current 
subspecies boundaries, acknowledged that the genetic data, as 
represented by nesting clades in Wood et al. (2008), argue for a much 
larger range that includes eastern populations of C. o. annulata (Rosen 
2008a, p. 11).
    According to most phylogenetic species concepts, the taxonomists 
(Boundy 2008, Burbrink 2008, Crother 2008b, Frost 2008) are using a 
criterion for species, not subspecies, and all four of these reviewers 
acknowledge that, following this reasoning, they do not believe 
subspecies are real biological units and that the concept of subspecies 
is antiquated. However, the Act recognizes conservation concern below 
the level of species by defining ``species'' to include subspecies and 
vertebrate Distinct Population Segments. Published lists of reptile and 
amphibian taxa, including those authored by our taxonomic peer 
reviewers (for example, Crother 2008a, Collins and Taggart 2009 (F. 
Burbrink is an author on the snake section)), still include subspecies, 
and the International Code of Zoological Nomenclature (ICZN), a 
universally accepted system of nomenclature (Frost et al. 2009, pp. 
136-137), includes articles pertaining to the naming of subspecies 
(ICZN 1999). Therefore, we continue to recognize subspecies as unique 
taxonomic entities, including the Tucson shovel-nosed snake.
    Additionally, mitochondrial DNA, as analyzed by Wood et al. (2008), 
represents a single genetic locus that accumulates mutations relatively 
slowly, and therefore differences between groups based on mitochondrial 
DNA typically reflect historical separation of groups rather than more 
recent population-level differences (Fallon 2007a, p. 1191). As a 
result, differentiation at mitochondrial genes reflects deep historical 
separation rather than more recent divergence, and does not reflect 
evolutionary difference shaped by the organism's ecology and 
environment (Fallon 2007a, p. 1191). Genetic differences among groups 
that have experienced more recent separation (such as those below the 
species level) may require combinations

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of markers and/or additional genetic data to reveal variation, if it 
exists (Fallon 2007a, p. 1192). Microsatellites provide a highly 
variable marker widely accepted as appropriate for detecting changes at 
this level (Fallon 2007a, p. 1191), and would be applicable in 
determining the subspecies status of the Tucson shovel-nosed snake.
    For the available information we considered, we find that 
uncertainty exists in both the taxonomic entity and subspecies range of 
C. o. klauberi. Information submitted by four of the six experts who 
provided input on these issues indicated that, while there are certain 
aspects of existing information that support rejecting the petitioned 
entity, there is uncertainty, and additional work is needed to clarify 
the validity and distribution of the subspecies (Boundy 2008, p. 3; 
Burbrink 2008, p. 2; Crother 2008b, p. 3; Holm 2008, p. 2). 
Specifically, they suggest that nuclear DNA markers or microsatellites 
be used to determine if C. o. klauberi is distinct, and if so, where 
the boundary between it and the intergrade zone is actually located. 
Public comment received related to this 12-month finding both supported 
the need for nuclear DNA markers or microsatellites (Arizona Game and 
Fish Department 2008, p. 3; Fallon 2007b, pp. 1-2; Jones 2008, p. 2), 
as well as questioned the validity of the subspecies based on Wood et 
al. (2008) (Carothers et al. 2008, pp. 9-14; James 2008, pp. 4-5; 
Taczanowsky 2008, pp. 1-2; Warren 2008, pp. 1 and 6). Therefore, 
because we received inconclusive expert opinion regarding the 
subspecies status of the Tucson shovel-nosed snake, as well as 
recommendations that further genetic study (nuclear DNA or 
microsatellites) is needed before this determination can be made, we 
regard the currently recognized taxonomic status and distribution of C. 
o. klauberi (Mardt et al. 2001) as the best available science, with the 
understanding that, as we acquire more information, the definition of 
this taxonomic entity (including its range) may change, and our finding 
may need to be revisited.

Biology

    The diet of shovel-nosed snakes consists of a variety of 
invertebrates, including scorpions, beetle larvae, spiders, crickets, 
centipedes, native roaches, and ants, (Mattison 1989, p. 25; Rosen et 
al. 1996, pp. 22-23; Brennan and Holycross 2006, p. 98). Glass (1972, 
p. 447) and Rosen et al. (1996, p. 22) suggest that shovel-nosed snakes 
eat relatively frequently. The authors (pp. 22-23) further support this 
observation by noting that individual shovel-nosed snakes in captivity 
each consumed five to eight crickets per week and showed significant 
weight loss after a 2- to 3-week lapse in feeding.
    Like the other three subspecies of the western shovel-nosed snake, 
the Tucson shovel-nosed snake uses ``sand swimming'' as its primary 
locomotion. The snake moves using a sideways swaying motion while it is 
either on or under the sand or loose soil (Stebbins 2003, p. 393). 
Klauber (1951, p. 192) suggests that shovel-nosed snakes rarely move 
more than 30.5 m (100 ft) in one night, as they do not normally move 
great distances below the sand surface; however, Rorabaugh (2002, p. 
42) documented one shovel-nosed snake (C. o. annulata) that moved 37 m 
(121 ft) in about 2 hours. Shovel-nosed snakes were thought to be 
primarily nocturnal in activity, but specimens have been documented as 
active during crepuscular (dawn and dusk) and daylight hours (C. 
occipitalis: Rosen et al. 1996, pp. 21-22; C. o. annulata: Rorabaugh 
2002, pp. 42-43; Brennan and Holycross 2006, p. 98). Shovel-nosed 
snakes are predominantly active at air temperatures between 70 and 90 
degrees Fahrenheit (21 and 32 degrees Celsius) and when surface 
temperatures in the sun are between 75 and 115 degrees Fahrenheit (24 
and 46 degrees Celsius) (Klauber 1951, p. 187; Rorabaugh 2002, pp. 42-
43). Rosen et al. (1996, p. 21) and Rorabaugh (2002, p. 42) have also 
observed that shovel-nosed snakes have been documented to be active in 
the morning and just before sunset. Rosen et al. (1996, p. 21) further 
note that activity seems to be highest when summer and spring 
temperatures are moderate and when the relative humidity is high.
    Reproductive studies have not been conducted specific to C. o. 
klauberi; however, some information is available for shovel-nosed 
snakes in general, which appear similar to that of other fossorial 
(burrowing) North American desert snakes in which sperm formation 
coincides with the period of maximum aboveground activity (Goldberg and 
Rosen 1999, pp. 155 and 157). Reproductive activity for shovel-nosed 
snakes occurs in April through July, and the clutch size ranges from 
two to four eggs (Klauber 1951, p. 194; Goldberg and Rosen 1999, p. 
156), although Brennan and Holycross (2006, p. 98) state that clutch 
size is from two to nine eggs.
    Limited information suggests the existence of four age classes in 
the Western shovel-nosed snake, based on snout-to-vent length (SVL): 
0.5, 1.5, 2.5, and 3.5 years and older (Rosen et al. 1996, p. 12). Sex 
ratios for shovel-nosed snakes appear to be skewed towards males, but 
this is likely due to sampling bias, as most shovel-nosed snake 
sightings are on roads, and males likely cross roads more frequently in 
search of females (Rosen et al. 1996, p. 21). Rosen et al. (1996, p. 
21) observed 1 female to 1.21 male shovel-nosed snakes while on foot in 
the Mohawk Dunes, suggesting that the extreme skewing seen in road 
collection represents observational bias.
    Klauber (1951, p. 185) indicates that scattered sand hummocks, 
crowned with mesquite or other desert shrubs, are favorite refuges for 
shovel-nosed snakes. Rosen (2003, p. 8) suggests that the Tucson 
shovel-nosed snake is found in more productive creosote-mesquite 
floodplain environments, differing from the habitats preferred by other 
subspecies of the Western shovel-nosed snake. Rosen (2003, p. 8) 
describes the associated soils of the Tucson shovel-nosed snake as 
soft, sandy loams, with sparse gravel.

Distribution

    The subspecies was historically known from Pima County in the Avra 
and Santa Cruz valleys (Rosen 2003, p. 4) and from western Pinal and a 
portion of eastern Maricopa counties (Klauber 1951, p. 196).
    As of 2001, over one-third of the range of the Tucson shovel-nosed 
snake (Mardt et al. 2001, p. 731.2) had been converted to either urban 
development or agriculture (U.S. Geological Survey National Gap 
Analysis Program 2004). The area between the Tucson and Phoenix 
metropolitan areas is believed to encompass the majority of the current 
range of this subspecies, particularly west of Tucson northward along 
Avra Valley in Pima County to western Pinal County, and then north into 
eastern Maricopa County, although no systematic surveys have been 
conducted to assess the status of Tucson shovel-nosed snakes throughout 
their range (Arizona Game and Fish Department 2008, p. 2). The last 
verifiable record of the Tucson shovel-nosed snake in Pima County was 
in 1979, near the intersection of Avra Valley Road and Sanders Road in 
the Avra Valley (Rosen 2003, p. 10). Although habitat still exists in 
Pima County, the current distribution and abundance in Pima County is 
unknown. Most of the currently occupied range of the Tucson shovel-
nosed snake is believed to lie in southwestern Pinal County and eastern 
Maricopa County, where the most recent records occur (Rosen 2008b, p. 
8; Mixan and Lowery, p. 1).
    Survey efforts on the Florence Military Reservation (Mixan and 
Lowery

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2008) and in the northern Avra Valley (Rosen 2003, 2004, and 2008b) 
provide the only recent intensive survey data available. Dr. Rosen 
conducted road surveys in 2003, 2004, and 2007, as well as trap arrays 
in 2007. From the road surveys he detected four Tucson shovel-nosed 
snakes, plus one photo-vouchered specimen from 2006, all near Eloy and 
Picacho in Pinal County, Arizona (Rosen 2004, p. 18; 2008b, p. 2). The 
trap arrays, which were set in previously occupied habitat in Pima 
County, did not result in any Tucson shovel-nosed snake captures. In 
the spring and summer of 2008, the Arizona Game and Fish Department 
conducted Tucson shovel-nosed snake surveys on the Florence Military 
Reservation in Pinal County, Arizona. A total of 29 Tucson shovel-nosed 
snakes were found during these surveys: 6 within trap arrays west of 
State Route 79 and 23 as road kill mortalities on State Route 79 (Mixan 
and Lowery 2008, p. 5).
    In 2006, the Arizona Game and Fish Department coordinated attempts 
to collect shovel-nosed snake tissues for genetic analyses. Based on 
these efforts, populations are persisting in areas dominated by 
creosote flats along State Route 79, north of Florence and south of 
Florence Junction; along Maricopa Road (including State Route 238) 
between Maricopa and Gila Bend (likely including much of the Rainbow 
Valley and lower Vekol Wash); east of the San Tan Mountains; along 
State Route 349 between Maricopa and Casa Grande; south of Interstate 8 
near the northern boundary of the Tohono O'odham Reservation; and in 
the vicinity of the Santa Cruz Flats near Eloy and Picacho (Arizona 
Game and Fish Department 2008, p. 2).

Factors Affecting the Tucson Shovel-Nosed Snake

    Section 4 of the Act (16 U.S.C. 1533), and implementing regulations 
at 50 CFR 424, set forth procedures for adding species to the Federal 
Lists of Endangered and Threatened Wildlife and Plants. A species, 
subspecies, or distinct population segment of vertebrate taxa may be 
determined to be endangered or threatened due to one or more of the 
five factors described in section 4(a)(1) of the Act: (A) The present 
or threatened destruction, modification, or curtailment of its habitat 
or range; (B) overutilization for commercial, recreational, scientific, 
or educational purposes; (C) disease or predation; (D) the inadequacy 
of existing regulatory mechanisms; or (E) other natural or manmade 
factors affecting its continued existence. Below we provide a summary 
of our analysis of the threats to the Tucson shovel-nosed snake.

A. The present or threatened destruction, modification, or curtailment 
of its habitat or range.

Urban and Rural Development
    As of 2001, more than 20 percent of the area within the range of 
the Tucson shovel-nosed snake had been converted to urban development 
(U.S. Geological Survey National Gap Analysis Program 2004). The 
effects of urban and rural development are expected to increase as 
human populations increase. The human population in Arizona increased 
by 394 percent from 1960 to 2000 (Social Science Data Analysis Network 
2000, p. 1) and another 26.7 percent from 2000 to 2008 (U.S. Census 
Bureau 2008, p. 1). Since 2000, population growth rates in Arizona 
counties where the Tucson shovel-nosed snake historically occurred or 
may still occur have varied by county but are no less remarkable: 
Maricopa (28.7 percent); Pima (19.9 percent); and Pinal (82.1 percent) 
(U.S. Census Bureau 2008, p. 1). Increasing human populations threaten 
the Tucson shovel-nosed snake as further modification and loss of 
habitat is required to accommodate this growth.
    Human population growth trends in Arizona are expected to continue 
into the future. By 2030, projections estimate the population in 
Arizona will have more than doubled when compared to the 2000 
population estimate (U.S. Census Bureau 2005, p. 1). In particular, a 
wide swath (called the Sun Corridor ``Megapolitan'') from the 
international border in Nogales, through Tucson, Phoenix, and north 
past the Prescott area is predicted to house eight million people by 
2030 (Gammage et al. 2008, pp. 15 and 22-23). This Megapolitan 
encompasses the entire historical range of the Tucson shovel-nosed 
snake and would contain approximately 82.5 percent more residents in 
2030 than in 2000 (Gammage et al. 2008, pp. 22-23).
    In response to our 90-day finding on the Tucson shovel-nosed snake, 
we received information stating that the prospect of continuing 
development is no longer a threat to the snake because of current 
economic conditions, and that these conditions have not only halted 
most real estate projects in central Arizona, but have also eliminated 
the demand for State Trust land in central Arizona to be sold for 
development (James 2008, p. 10). We acknowledge that development 
pressure across Arizona has slowed due to the recent economic downturn 
and housing market collapse. However, this does not negate the fact 
that development likely still will continue in the future, although 
perhaps at a slower pace than in the earlier part of this century. For 
instance, the most recent draft Pinal County Comprehensive Plan 
(February 2009) acknowledges that the county is in the middle of the 
Sun Corridor Megapolitan (Tucson, Phoenix, and the corridor between 
them), and proposes four shorter-term Growth Areas to define areas 
where development will occur or be encouraged to develop over the next 
decade, although it does not mean to discourage growth outside of these 
areas (Pinal County Comprehensive Plan 2009, p. 109). These four Growth 
Areas (Gateway/Superstition Vistas, West Pinal, Red Rock, and Tri-
Communities) fall either completely or partially within the range of 
the Tucson shovel-nosed snake. The Gateway/Superstition Vistas Growth 
Area alone encompasses 71,225 hectares (176,000 acres, or 275 square 
miles) of State Trust land, at least two-thirds of which falls within 
the range of the snake, and it is anticipated that more than 800,000 to 
more than 1,000,000, people will one day live in this development 
(Pinal County Comprehensive Plan 2009, p. 115). The Comprehensive Plan 
(2009, p. 117) identifies many kilometers (miles) of new freeways and 
principal arterials in this Growth Area at buildout, which the plan 
acknowledges may take over a half century to realize (p. 115). Roads 
can have a negative effect on reptiles in general, and snakes 
specifically, and pose a threat to the Tucson shovel-nosed snake, as 
well. This is discussed in more detail in the Road Construction, Use, 
and Maintenance section below.
    Additionally, the Maricopa County Comprehensive Plan calls for 
Growth Areas to the south and east of the Chandler and Mesa areas, 
which are within the range of the Tucson shovel-nosed snake (Maricopa 
County Comprehensive Plan 2002 (revised), p. 92). City comprehensive 
plans within the range of the snake also call for future Growth Areas; 
for example, the City of Eloy has designated six Growth Areas 
encompassing 15,520 acres mostly along the Interstate 10 corridor (City 
of Eloy General Plan 2004, pp. 7-6 through 7-10), of which more than 
half fall within the range of the snake. These Growth Areas include the 
locations of some of the most recent sightings of the snake (Rosen 
2008b, p. 8). While much of this area has already been impacted by 
development or irrigated agriculture, any remaining habitat for the 
Tucson shovel-nosed snake will likely be negatively affected as 
development and

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its associated infrastructure progress into these areas.
    James (2008, p. 9) also stated that, as a consequence of 
restrictions imposed on both agricultural and municipal uses of 
groundwater by Arizona law, development within the range of the Tucson 
shovel-nosed snake, particularly in Pinal County, has primarily 
involved the conversion of agricultural land to municipal uses. 
Although James (2008, p. 9) considers the actual impact of development 
on suitable habitat for the Tucson shovel-nosed snake to be 
exaggerated, we did not find evidence to support this claim. As of 
2001, more than one third of the area within the range of the snake was 
in agricultural use or under development (U.S. Geological Survey 
National Gap Analysis Program 2004). We acknowledge that the conversion 
of agricultural land to municipal uses has occurred and continues to 
occur within the range of the Tucson shovel-nosed snake (as noted 
above). Much of the land in the western half of Pinal County is 
primarily used for irrigated agriculture because of low desert valleys 
(Arizona Department of Agriculture 2009, p. 1), which includes a large 
portion of the range of the Tucson shovel-nosed snake. However, the 
above-mentioned Gateway/Superstition Vistas Growth Area occurs on 
71,225 hectares (176,000 acres, or 275 square miles) of Arizona State 
Trust land that, while portions of it are moderately grazed, are not 
currently in irrigated agriculture. Additionally, conversion from 
agriculture to residential development involves building additional 
roadways and transportation corridors, which may negatively affect the 
snake, even in pockets of remaining habitat (see Road Construction, 
Use, and Maintenance section below). Therefore, while development may 
be occurring on lands that were already compromised by a previous use, 
it still poses a threat, as areas of remaining habitat (especially 
within the Sun Corridor Megapolitan) are expected to be developed for 
residential and commercial use over the next decade and beyond.
Road Construction, Use, and Maintenance
    As noted in the previous section, roadways and transportation 
corridors are expected to increase over the next decade and beyond as 
counties within the range of the Tucson shovel-nosed snake, and 
particularly in Pinal County, continue to develop residential and 
commercial infrastructure. Roads pose unique threats to herpetofauna 
and specifically to the Tucson shovel-nosed snake, its prey base, and 
the habitat where it occurs through: (1) fragmentation, modification, 
and destruction of habitat; (2) increased genetic isolation; (3) 
alteration of movement patterns and behaviors; (4) facilitation of the 
spread of non-native species via human vectors; (5) increased 
recreational access and the likelihood of subsequent, decentralized 
urbanization; (6) interference with or inhibition of reproduction; and 
(7) population sinks through direct mortality (resulting in unnaturally 
high death rates that exceed birth rates within a population) (Rosen 
and Lowe 1994, pp. 146-148; Carr and Fahrig 2001, pp. 1074-1076; Hels 
and Buchwald 2001, p. 331; Smith and Dodd 2003, pp. 134-138; Angermeier 
et al. 2004, pp. 19-24; Shine et al. 2004, pp. 9-11; Andrews and 
Gibbons 2005, pp. 777-781; Roe et al. 2006, p. 161).
    Roe et al. (2006, p. 161) conclude that mortality rates due to 
roads are higher in mobile species, such as shovel-nosed snakes (active 
hunters), than those of more sedentary species, which more commonly 
employ sit-and-wait foraging strategies. Mixan and Lowery (2008, p. 5) 
found 23 Tucson shovel-nosed snakes dead on the road near the Florence 
Military Reservation over 45 days of survey efforts, indicating this 
subspecies is vulnerable to road mortality. The effect of road 
mortality of snakes becomes most significant in the case of small, 
highly fragmented populations where removal of mature females from the 
population may appreciably degrade the viability of a population. 
Additionally, if snakes traverse only 37 m (121 ft) each night 
(Rorabaugh 2002, p. 42), roads that are wider than this may serve as 
barriers, further fragmenting the population.
    Off-highway vehicle (OHV) use has grown considerably in Arizona. As 
of 2007, 385,000 OHVs were registered in Arizona (a 350 percent 
increase since 1998) and 1.7 million people (29 percent of the 
Arizona's public) engaged in off-road activity from 2005 to 2007 (Sacco 
2007, pers. comm.). Over half of OHV users reported that merely driving 
off-road was their primary activity, versus using the OHV for the 
purpose of hunting, fishing, or hiking (Sacco 2007, pers. comm.). Given 
the pervasive use of OHVs on the landscape, OHV-related mortalities are 
likely a threat to Tucson shovel-nosed snakes. Ouren et al. (2007, pp. 
16-22) provided additional data on the effects of OHV use on wildlife. 
Specifically, OHV use may cause mortality or injury to species that 
attempt to cross trails created through occupied habitat, and may even 
lead to depressed populations of snakes depending on the rate of use 
and number of trails within a given area (Ouren et al. 2007, pp. 20-
21). This threat may be even more extensive from OHVs than from 
conventional vehicles because OHV trails often travel through 
undeveloped habitat. In particular, the Gateway/Superstition Vistas 
Growth Area has been and continues to be impacted by OHV use, although 
the Arizona State Land Department is in the process of fencing off a 
part of this area for dust-abatement reasons (Windes 2009, pers. 
comm.).
Solar Power Facilities and Transmission Corridors
    Solar radiation levels in the Southwest, including Arizona, are 
some of the highest in the world, and interest in tapping into this 
source of potential energy is growing. Of the solar technologies 
available to harness this energy, Concentrating Solar Power (CSP) 
technologies are the most likely to be used, although photovoltaic 
cells could be used in some cases. CSP technologies use mirrors to 
reflect and concentrate sunlight onto receivers that collect solar 
energy and convert it to heat. This thermal energy can then be used to 
produce electricity via a steam turbine or heat engine driving a 
generator.
    Within Arizona, the Bureau of Land Management (BLM) has received 35 
solar right-of-way applications, including one that is pending on 850 
hectares (2,100 acres) approximately 19 kilometers (12 miles) south of 
Eloy, which is within the range of the Tucson shovel-nosed snake (BLM 
2009b, p. 1 and map). Additionally, within Arizona, the Arizona State 
Land Department is considering solar projects on some of the lands 
under its jurisdiction. These potential sites are mostly west of 
Phoenix and Gila Bend, but one project could be located along 
Interstate 10 in the vicinity of Red Rock, which is within the range of 
the Tucson shovel-nosed snake. Little information is available about 
these projects, so we do not know the exact location or extent of each 
project (Scott 2009, p. 29).
    Solar energy development and transmission corridors pose similar 
threats to the Tucson shovel-nosed snake as development and roadway 
projects (see Rural and Urban Development and Road Construction, Use, 
and Maintenance sections above). An average utility-scale solar 
facility to generate 250 megawatts of electricity would occupy about 
506 hectares (1,250 acres) of land (BLM 2009a, p. 1), and would involve 
removal of all vegetation within this area. Additionally, CSP 
facilities employ liquids such as oils or molten salts to create steam 
to power conventional turbines and generators, as

[[Page 16055]]

well as various industrial fluids, such as hydraulic fluids, coolants, 
and lubricants, all of which may present a contaminants-related risk 
should these fluids leak onto the ground (Scott 2009, p. 12). New 
transmission lines would need to be built to these facilities, as well 
as additional roads to maintain the facilities, likely increasing 
traffic in these areas. These activities pose a threat to the Tucson 
shovel-nosed snake through removal and contamination of remaining 
habitat and increased potential for road kill mortality.
Agricultural Uses
    While the number of farms in Arizona has almost doubled since 1997, 
the total amount of farmed area has decreased (U.S. Department of 
Agriculture 2009, p. 7). Within Maricopa, Pima, and Pinal counties, the 
amount of irrigated farmland decreased from 2002 to 2007 by 13.5 
percent (58,724 hectares (145,109 acres)), 4.1 percent (3,327 hectares 
(8,222 acres), and 0.7 percent (2,366 hectares (5,846 acres)), 
respectively (U.S. Department of Agriculture 2009, p. 273). This 
decrease in irrigated farmland is likely due to the conversion of 
agricultural areas to urban development. As of 2001, more than 10 
percent of the area within the range of the Tucson shovel-nosed snake 
had been converted to agriculture (U.S. Geological Survey National Gap 
Analysis Program 2004).
    Pinal County is the county with the most agricultural production 
within the range of the Tucson shovel-nosed snake. In 2007, the amount 
of farmland still in production in Pinal County was 125,420 hectares 
(309,920 acres), or approximately nine percent of the entire county 
(U.S. Department of Agriculture 2009, p. 273). Much of this land, 
however, is in the western half of the county (Arizona Department of 
Agriculture 2009, p. 1), which is within the range of the Tucson 
shovel-nosed snake. Conversion of low desert valleys to farmland 
renders habitats unsuitable for the Tucson shovel-nosed snake. 
Agricultural practices can impact this subspecies in a number of ways. 
Farmers typically use pesticides and herbicides to maintain high 
agricultural yields, but because arthropods are the primary food for 
the snake (Mattison 1989, p. 25; Rosen et al. 1996, pp. 22-23), the 
loss or contamination of this prey base may cause mortality, impaired 
health, or abandonment of an area. Additionally, traffic associated 
with agricultural roads can result in mortality of individuals (see 
Road Construction, Use, and Maintenance section above).
Wildfires
    Fire has become an increasingly significant threat in the Sonoran 
Desert. Esque and Schwalbe (2002, pp. 180-190) discuss the effect of 
wildfires in the Arizona Upland and Lower Colorado River subdivisions 
of Sonoran desertscrub, both of which are found in the range of the 
Tucson shovel-nosed snake. The widespread invasion of non-native annual 
grasses appears to be largely responsible for altered fire regimes that 
have been observed in these communities, which are not adapted to fire 
(Esque and Schwalbe 2002, p. 165). In areas comprised entirely of 
native species, ground vegetation density is mediated by barren spaces 
that do not allow fire to carry across the landscape. However, in areas 
where non-native grasses have become established, the fine fuel load is 
continuous, and fire is capable of spreading quickly and efficiently 
(Esque and Schwalbe 2002, p. 175). Non-native annual grasses prevalent 
within the range of the Tucson shovel-nosed snake include brome grasses 
(Bromus rubens and B. tectorum) and Mediterranean grasses (Schismus 
spp.) (Esque and Schwalbe 2002, p. 165). The perennial African 
buffelgrass (Pennisetum ciliare), which also poses a fire risk to 
Sonoran desertscrub, is prevalent within the range of the snake in the 
Avra and Santa Cruz valleys (Van Devender and Dimmit 2006, p. 5), as 
well as along Interstate 10 to the City of Phoenix (Kidnocker 2009, p. 
1).
    After disturbances such as fire, non-native grasses may exhibit 
dramatic population explosions, which hasten their effect on native 
vegetation communities. Additionally, with increased fire frequency, 
these population explosions may lead to a type-conversion of the 
vegetation community from desert scrub to grassland (Esque and Schwalbe 
2002, pp. 175-176; Overpeck and Weiss 2005, p. 2075). Fires carried by 
the fine fuel loads created by non-native grasses often burn at 
unnaturally high temperatures, which may result in soils becoming 
hydrophobic (water repelling), exacerbating sheet erosion, and 
contributing large amounts of sediment to receiving drainages and water 
bodies (Esque and Schwalbe 2002, pp. 177-178). Buffelgrass, in 
particular, is acknowledged as one of the most serious invasive weeds 
in the Sonoran Desert due to its ability to spread exponentially 
(Buffelgrass Working Group 2007, p. 2). It has the potential to invade 
much of southern and central Arizona, which can lead to recurring 
grassland fires and the destruction of native desert vegetation 
(Buffelgrass Working Group 2007, p. 2). These changes can negatively 
affect the habitat and prey base of the Tucson shovel-nosed snake, 
although precisely how snake populations would respond is unknown.
Summary of Factor A
    Much of the habitat within the range of the Tucson shovel-nosed 
snake already has been converted to development or agriculture, and 
remaining habitat continues to be threatened by both these land uses, 
as well as the construction of large-scale solar power facilities and 
transmission lines. By the year 2030, the human population in Arizona 
is expected to be more than double the 2000 population, particularly in 
the Sun Corridor Megapolitan, which is an area completely encompassing 
the range of the Tucson shovel-nosed snake. Road construction, 
maintenance, and use have been documented to affect this subspecies 
directly through mortality and indirectly through habitat loss and 
fragmentation, the impacts of which will likely increase with new 
development and an increasing human population. The need for 
alternative energy sources is continuing to rise, which will lead to 
construction of solar energy facilities and transmission corridors in 
the State of Arizona, some of which will likely be sited within the 
range of the Tucson shovel-nosed snake. Agricultural use within the 
range of the snake has been decreasing, a trend that will probably 
continue as land use converts from agriculture to residential and 
commercial development. Agriculture that persists will continue to 
impact the snake by reducing the available prey base and fragmenting 
habitat. The threat of wildfire due to non-native plants is expected to 
rise, given the prevalence of Mediterranean grasses, brome grasses, and 
especially buffelgrass within the range of the Tucson shovel-nosed 
snake and the invasive nature of these grasses. How snakes would 
respond to vegetation community change brought about by increasing fire 
frequency is unknown. The best available information indicates shovel-
nosed snakes travel only short distances (37 m (121 ft)), which likely 
makes the subspecies particularly susceptible to habitat fragmentation 
as barriers formed by the above-mentioned threats isolate small 
populations from one another. Therefore, we find that the present or 
threatened destruction, modification, or curtailment of its habitat or 
range is a threat to the Tucson shovel-nosed snake within the 
foreseeable future.

[[Page 16056]]

B. Overutilization for commercial, recreational, scientific, or 
educational purposes.

    Based on the information available, overutilization of the Tucson 
shovel-nosed snake does not appear to pose a threat to this subspecies. 
Shovel-nosed snakes in general, and Tucson shovel-nosed snakes in 
particular, are not regularly seen in the pet trade (Arizona Game and 
Fish Department 2008). There have been few scientific or educational 
studies of Tucson shovel-nosed snakes over the years, and most recently 
they have been limited largely to surveys (Arizona Game and Fish 
Department 2008). Few animals have been collected for these studies 
other than animals found on highways, where their survival was already 
likely compromised. Additionally, Arizona State University and the 
University of Arizona recently began to accept photographic vouchers, 
versus physical specimens, in their respective museum collections, 
which may reduce the amount of collection. We believe these measures 
reduce the necessity for field biologists to collect physical specimens 
(unless discovered postmortem) for locality voucher purposes and, 
therefore, further reduce impacts to vulnerable populations of the 
Tucson shovel-nosed snake. Based on this information, we find that 
overutilization for commercial, recreational, scientific, or 
educational purposes is not a threat to the Tucson shovel-nosed snake.

C. Disease or Predation

    Disease in Tucson shovel-nosed snakes has not yet been documented 
as a specific threat. However, little is known about disease in wild 
snakes. Predation on Chionactis occipitalis by a variety of carnivores 
has been documented, including by various snakes, foxes, coyotes, 
shrikes, and owls (Brennan and Holycross 2006, p. 98). However, we are 
not aware of data suggesting that predation poses a threat beyond that 
expected in a normally functioning ecosystem. Therefore, we do not 
consider disease or predation a threat to Tucson shovel-nosed snakes.

D. Inadequacy of existing regulatory mechanisms.

    The Tucson shovel-nosed snake is considered a ``Tier 1b Species of 
Greatest Conservation Need'' in the Arizona Game and Fish Department 
draft document, Arizona's Comprehensive Wildlife Conservation Strategy 
(CWCS) (Arizona Game and Fish Department 2006, pp. 32 and 723). The 
purpose of the CWCS is to provide a foundation for the future of 
wildlife conservation and a stimulus to conservation partners to 
strategically think about their roles in prioritizing conservation 
efforts (Arizona Game and Fish Department 2006, p. 2). A Tier 1b 
species is one that requires immediate conservation actions aimed at 
improving conditions through intervention at the population or habitat 
level (Arizona Game and Fish Department 2006, p. 32). The CWCS, 
however, does not provide regulatory protection for the snake. It 
serves only to prioritize funds and guide implementation of 
conservation activities for Arizona's vulnerable wildlife (Arizona Game 
and Fish Department 2006, p. 9). The Arizona Game and Fish Department 
does not have specified or mandated recovery goals for the Tucson 
shovel-nosed snake, but it continues as a strong partner in research 
and survey efforts that further our understanding of current 
populations within Arizona.
    With a valid hunting license, the Arizona Game and Fish Department 
allows for take of up to four Tucson shovel-nosed snakes per person per 
year as specified in Commission Order Number 43. The Arizona Game and 
Fish Department defines ``take'' as ``pursuing, shooting, hunting, 
fishing, trapping, killing, capturing, snaring, or netting wildlife or 
the placing or using any net or other device or trap in a manner that 
may result in the capturing or killing of wildlife.'' If more than four 
are to be collected (e.g., for research purposes), a scientific 
collecting permit must be obtained. It is illegal to commercially sell, 
barter, or trade any native Arizona wildlife.
    While we are aware that the Arizona Game and Fish Department 
enforces these laws to the extent that it can, encounters between 
humans and Tucson shovel-nosed snakes can result in the capture, 
injury, or death of the snake due to the lay person's fear or dislike 
of snakes, and the snake's resemblance to venomous coral snakes (Rosen 
and Schwalbe 1988, p. 43; Ernst and Zug 1996, p. 75; Green 1997, pp. 
285-286; Nowak and Santana-Bendix 2002, p. 39). We believe that 
unregulated take may occur, but it is likely infrequent because Tucson 
shovel-nosed snakes generally are difficult to locate in the wild.
    The majority of currently known populations of Tucson shovel-nosed 
snakes occur on lands managed by the Arizona State Land Department, 
which at present has no regulations or programs to protect the 
subspecies. State Trust Land is distinguished from public land (such as 
Federal land administered by the BLM or U.S. Forest Service) in that 
all uses of the land must benefit the 13 Trust beneficiaries, the 
largest of which are the Common Schools (Arizona State Land Department 
2009a, p. 1). Arizona State Trust Lands are managed to enhance value 
and optimize economic return for the Trust beneficiaries (Arizona State 
Land Department 2009b, p. 1), which can include the sale or long-term 
lease of lands for commercial or residential development. Although 
State lands currently provide open space within the range of the Tucson 
shovel-nosed snake, there are no known plans to require protection of 
habitat on State lands, and no other protections are afforded the snake 
on State lands.
    BLM manages some lands within the range of the Tucson shovel-nosed 
snake. BLM currently has no regulations to protect the Tucson shovel-
nosed snake, and does not survey for the snake or its habitat. BLM 
lands usually are secure from agricultural and urban development; 
however, BLM may dispose of lands identified under its land use 
planning through the Federal Land Policy and Management Act of 1976 (43 
U.S.C. 1701 et seq.), and may also issue permits for uses such as solar 
facilities and rights-of-way. Additionally, the open space provided by 
BLM lands can be and often is heavily impacted by OHV use, which may 
pose a threat to the Tucson shovel-nosed snake (see Road Construction, 
Use, and Maintenance under Factor A above).
    Some lands within the range of the Tucson shovel-nosed snake are 
owned by county, city, or private entities. These lands may provide 
habitat for the Tucson shovel-nosed snake if they are maintained as 
natural open space; however, there are no regulatory mechanisms in 
place to protect the snake should the land use change.
    We are aware of three habitat conservation plans currently being 
developed that include the Tucson shovel-nosed snake as a covered 
species: the Pima County Multi-species Conservation Plan, the Town of 
Marana Habitat Conservation Plan, and the City of Tucson's Avra Valley 
Habitat Conservation Plan. As none of these plans have been finalized, 
we will not explore the adequacies of these plans as possible 
regulatory mechanisms for the snake.
    The Gila River Indian Community owns lands within the range of the 
Tucson shovel-nosed snake. We are not aware of any mechanisms in place 
to protect the snake on their lands.

[[Page 16057]]

Summary of Factor D
    Currently, there are no regulatory mechanisms in place that 
specifically target the conservation of the Tucson shovel-nosed snake 
or its habitat. Regulations protecting the quantity and quality of open 
space are inadequate to protect the habitat of the Tucson shovel-nosed 
snake, particularly in the face of the significant population growth 
expected within the historical range of the snake discussed under 
Factor A. Therefore, we consider the inadequacy of existing regulatory 
mechanisms a threat to the Tucson shovel-nosed snake.

E. Other natural or manmade factors affecting its continued existence.

    Seager et al. (2007, pp. 1181-1184) analyzed 19 different computer 
models of differing variables to estimate the future climatology of the 
southwestern United States and northern Mexico in response to 
predictions of changing climatic patterns. All but one of the 19 models 
predicted a drying trend within the Southwest; one predicted a trend 
toward a wetter climate (Seager et al. 2007, p. 1181). A total of 49 
projections were created using the 19 models; all but 3 of the 
projections predicted a shift to increasing dryness in the Southwest as 
early as 2021-2040 (Seager et al. 2007, p. 1181). The current prognosis 
for climate change impacts on the Sonoran Desert of the American 
Southwest includes fewer frost days; warmer temperatures; greater water 
demand by plants, animals, and people; and an increased frequency of 
extreme weather events (heat waves, droughts, and floods) (Overpeck and 
Weiss 2005, p. 2074; Archer and Predick 2008, p. 24). How climate 
change will affect summer precipitation is less certain, because 
precipitation predictions are based on continental-scale general 
circulation models that do not yet account for land use and land cover 
change effects on climate or regional phenomena, such as those that 
control monsoonal rainfall in the Southwest (Overpeck and Weiss 2005, 
p. 2075; Archer and Predick 2008, pp. 23-24). Some models predict 
dramatic changes in Southwestern vegetation communities as a result of 
climate change (Overpeck and Weiss 2005, p. 2074; Archer and Predick 
2008, p. 24), especially as wildfires carried by non-native plants 
(e.g., buffelgrass) potentially become more frequent, promoting the 
presence of exotic species over native ones (Overpeck and Weiss 2005, 
p. 2075). The shovel-nosed snake currently persists, often in 
abundance, within portions of its range (e.g., southwestern Arizona and 
southeastern California) that experience less precipitation and higher 
temperatures and are characterized by simpler vegetation communities 
(Turner and Brown 1982, pp. 190-202) than that found within the range 
of the Tucson shovel-nosed snake. Hence, if climates dry and become 
warmer, with concomitant changes in vegetation communities, the Tucson 
shovel-nosed snake may be able to persist under those conditions. 
However, the precise habitat components and ecological relationships 
necessary for persistence are unknown, so predicting the response of 
the snake to environmental change induced by climate change is 
speculative. If changes include increased fire frequency due to 
increasing non-native plants, this tends to increase uncertainty in 
predicting population response, because how the snake responds to these 
fire-altered communities is unknown. At this time, it is not possible 
to determine how these changes will affect the Tucson shovel-nosed 
snake, as potential trajectories of vegetation change within the range 
of the subspecies are difficult to predict due to uncertain changes in 
warm season precipitation variability and fire (Overpeck and Weiss 
2005, p. 2075), and the response of the snake to changing vegetation 
communities is speculative.
Summary of Factor E
    Temperatures in the desert Southwest are expected to rise in the 
next two decades and likely throughout the 21\st\ century 
(Intergovernmental Panel on Climate Change 2007, pp. 45-46), with an 
increased frequency of extreme weather events, such as heat waves, 
droughts, and floods. We do not know the extent to which changing 
climate patterns will affect the Tucson shovel-nosed snake; however, 
this environmental change injects additional uncertainty into the 
future status of the subspecies.

Finding

    In our review of the status of the Tucson shovel-nosed snake, we 
carefully examined the best scientific and commercial information 
available. We identified a number of potential threats to this species, 
including: urban and rural development; road construction, use, and 
maintenance; concentrating solar power facilities and transmission 
corridors; agriculture; wildfires; and lack of adequate management and 
regulation.
    Limited surveys have been conducted only in small parts of its 
range, so information on rangewide population size and trends for the 
Tucson shovel-nosed snake is not available. As of 2001, over one-third 
of the area within the range of the snake had been converted to either 
urban development or agriculture. There are indications that in the 
Avra Valley, where the snake was once present, it has now disappeared 
or persists in such low numbers that it is difficult to locate. In 
other areas (e.g., Florence Military Reservation), the snake appears to 
be persisting. Therefore, based on the best available information, we 
find that the only information we have indicates that populations in 
the Avra Valley have declined, which is near development and 
agriculture; while in areas with little or no development or 
agriculture, the population is persisting.
    We evaluated existing and potential threats to the Tucson shovel-
nosed snake to determine what effects on the subspecies are currently 
occurring, whether these threats are likely to increase or decrease in 
the future, and which of the impacts may be expected to rise to the 
level of a threat to the subspecies, either rangewide or at the 
population level. We examined threats posed by urban and rural 
development; road construction, use, and maintenance; solar power 
facilities and transmission corridors; agricultural uses; wildfires; 
overutilization; disease and predation; the inadequacy of existing 
regulatory mechanisms; and climate change. We did not find that 
overutilization, disease, or predation are currently threatening the 
Tucson shovel-nosed snake. We also found it likely that the threat of 
agricultural uses will decrease in the future, as farmland is and will 
continue to be converted to residential and commercial uses.
    Next we considered whether any of the potential threats are likely 
to increase within the foreseeable future. Data suggest that urban and 
rural development in most of the snake's range is likely to increase in 
the future. Comprehensive Plans encompassing the entire range of the 
snake encourage large Growth Areas in the next 20 years and beyond, 
portions of which occur in Tucson shovel-nosed snake habitat not 
already impacted by development or agriculture. These Plans also call 
for an increase in roads and transportation corridors, which have been 
documented to impact the snake through direct mortality. Additionally, 
development of solar energy facilities and transmission corridors 
throughout the State is being pursued, and demand for these facilities 
will likely increase. Some of these facilities are being considered 
within the range of the Tucson shovel-nosed snake and have the 
potential to degrade

[[Page 16058]]

or destroy approximately 506 hectares (1,250 acres), on average, of 
habitat per facility. We also believe that wildfires due to 
infestations of non-native grasses (especially buffelgrass) in the 
snake's habitat, which has native plants not adapted to survive 
wildfires, are likely to increase in frequency and magnitude in the 
future as these invasive grasses continue to spread rapidly. It appears 
that the snake only travels short distances, which makes the subspecies 
particularly susceptible to habitat fragmentation, as barriers created 
by development, roads, solar facilities, and wildfires isolate 
populations from one another. We found that regulations are not in 
place to minimize or mitigate these threats to the Tucson shovel-nosed 
snake and its habitat, and, therefore, they are likely to put the snake 
at risk of local extirpation or extinction.
    Climate change is likely to continue for the next century, but 
there is uncertainty as to how climate change, described under Factor 
E, will affect the Tucson shovel-nosed snake and its habitat. 
Predictions are that temperatures in the Southwestern United States 
will continue to increase, with extreme weather events (such as heat 
waves, drought, and flooding) occurring with more frequency. How summer 
precipitation may be affected is less certain. Current models suggest 
that a 10- to 20-year (or longer) drought is anticipated, and some 
models predict dramatic changes in Southwestern vegetation communities 
as a result of climate change, although trajectories of vegetation 
change are difficult to predict because of variability in warm season 
precipitation and fire frequency. These changes could affect the 
habitat of the Tucson shovel-nosed snake, but because of the lack of 
specific modeling data within the range of the snake, we cannot predict 
how climate change will impact the Tucson shovel-nosed snake now or in 
the foreseeable future.
    We next considered whether the existing level of threats causes us 
to conclude that the species is in danger of extinction now or in the 
foreseeable future. The threats discussed above, particularly those 
that lead to a loss of habitat, are likely to reduce the population of 
Tucson shovel-nosed snakes across its entire range. Given the limited 
geographic distribution of this snake and the fact that its entire 
range lies within the path of future development, we believe the 
subspecies is likely to become in danger of extinction within the 
foreseeable future. Therefore, we find that listing the Tucson shovel-
nosed snake throughout its range is warranted.
    We have reviewed the available information to determine if the 
existing and foreseeable threats pose an emergency. We have determined 
that an emergency listing is not warranted for this subspecies at this 
time because, within the current distribution of the subspecies 
throughout its range, there are at least some populations of the Tucson 
shovel-nosed snake that exist in relatively natural conditions that are 
unlikely to change in the short-term. However, if at any time we 
determine that emergency listing of the Tucson shovel-nosed snake is 
warranted, we will initiate an emergency listing.
    The Service adopted guidelines on September 21, 1983 (48 FR 43098) 
to establish a rational system for allocating available appropriations 
to the highest priority species when adding species to the Lists of 
Endangered or Threatened Wildlife and Plants or reclassifying 
threatened species to endangered status. The system places greatest 
importance on the immediacy and magnitude of threats, but also factors 
in the level of taxonomic distinctiveness by assigning priority in 
descending order to monotypic genera, full species, and subspecies (or 
equivalently, distinct population segments of vertebrates). We assigned 
the Tucson shovel-nosed snake an LPN of 3, based on our finding that 
the subspecies faces imminent and high-magnitude threats from the 
present or threatened destruction, modification, or curtailment of its 
habitat and the inadequacy of existing regulatory mechanisms. One or 
more of the threats discussed above is occurring or is expected to 
occur throughout the entire range of this subspecies. These threats are 
on-going and, in some cases (e.g., loss of habitat through urban 
development), considered irreversible. While we conclude that listing 
the Tucson shovel-nosed snake is warranted, an immediate proposal to 
list this subspecies is precluded by other higher priority listing, 
which we address below.

Significant Portion of the Range

    The Act defines an endangered species as one ``in danger of 
extinction throughout all or a significant portion of its range,'' and 
a threatened species as one ``likely to become an endangered species 
within the foreseeable future throughout all or a significant portion 
of its range.'' The term ``significant portion of its range'' is not 
defined by