Endangered and Threatened Wildlife and Plants; 90-Day Finding on a Petition To List the Northern Mexican Gartersnake as Threatened or Endangered With Critical Habitat, 315-324 [06-1]

Agencies

• Fish and Wildlife Service
• DEPARTMENT OF THE INTERIOR

[Federal Register Volume 71, Number 2 (Wednesday, January 4, 2006)]
[Proposed Rules]
[Pages 315-324]
From the Federal Register Online via the Government Printing Office [www.gpo.gov]
[FR Doc No: 06-1]


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DEPARTMENT OF THE INTERIOR

Fish and Wildlife Service

50 CFR Part 17


Endangered and Threatened Wildlife and Plants; 90-Day Finding on 
a Petition To List the Northern Mexican Gartersnake as Threatened or 
Endangered With Critical Habitat

AGENCY: Fish and Wildlife Service, Interior.

ACTION: Notice of 90-day petition finding and initiation of status 
review.

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SUMMARY: We, the U.S. Fish and Wildlife Service (Service), announce a 
90-day finding on a petition to list the northern Mexican gartersnake, 
Thamnophis eques megalops, as threatened or endangered with critical 
habitat under the Endangered Species Act of 1973, as amended (Act). The 
petitioners provided three listing scenarios for consideration by the 
Service: (1) Listing the United States population as a Distinct 
Population Segment (DPS); (2) listing the species throughout its range 
in the United States and Mexico based on its range-wide status; or (3) 
listing the species throughout its range in the U.S. and Mexico based 
on its status in the United States. We find the petition has presented 
substantial information that the northern Mexican gartersnake is a 
listable entity, and we find that the petition presents substantial 
scientific and commercial data indicating that listing may be 
warranted. Therefore, we are initiating a status review to determine if 
listing this species is warranted. To ensure that the status review is 
comprehensive, we are soliciting scientific and commercial information 
regarding this species. Any determinations on critical habitat will be 
made if and when a listing action is initiated for this species.

DATES: The finding announced in this document was made on December 13, 
2005. To be considered in the 12-month finding for this petition, 
comments and information should be submitted to us by March 6, 2006.

ADDRESSES: Data, information, comments, or questions concerning this 
petition and our finding should be submitted to the Field Supervisor, 
Arizona Ecological Services Field Office, 2321 West Royal Palm Drive, 
Suite 103, Phoenix, Arizona. The petition, supporting data, and 
comments will be available for public inspection, by appointment, 
during normal business hours at the above address.
    If you wish to comment or provide information, you may submit your 
comments and materials by any one of the following methods:
    1. You may submit written comments and information by mail to: 
Field Supervisor, Arizona Ecological Services Field Office, 2321 West 
Royal Palm Drive, Suite 103, Phoenix, Arizona.
    2. You may hand-deliver written comments and information to our 
Field Supervisor, Arizona Ecological Services Field Office, 2321 West 
Royal Palm Drive, Suite 103, Phoenix, Arizona.
    3. You may fax your comments to 602-242-2513.
    4. You may send your comments by electronic mail (e-mail) directly 
to the Service at MexGsnake@fws.gov, or to the Federal Rulemaking 
Portal at https://www.regulations.gov. Please include ``Attn: northern 
Mexican gartersnake'' in the beginning of your message, and do not use 
special characters or any form of encryption. Electronic attachments in 
standard formats (such as .pdf or .doc) are acceptable, but please name 
the software necessary to open any attachments in formats other than 
those given above. Also, please include your name and return address in 
your e-mail message. If you do not receive a confirmation from the 
system that we have received your e-mail message, please submit your 
comments in writing using one of the alternate methods described above. 
In the event that our internet connection is not functional, please 
submit your comments by the alternate methods mentioned above.

FOR FURTHER INFORMATION CONTACT: Steve Spangle, Field Supervisor, 
Arizona Ecological Services Field Office (telephone 602-242-0210 and 
facsimile 602-242-2513).

SUPPLEMENTARY INFORMATION:

Public Information Solicited

    When we make a finding that substantial information is presented to 
indicate that listing a species may be warranted, we are required to 
promptly commence a review of the status of the species. To ensure that 
the status review is complete and based on the best available 
scientific and commercial information, we are soliciting information on 
the northern Mexican gartersnake. We request any additional 
information, comments, and suggestions from the public, other concerned 
governmental agencies, Native American Tribes, the scientific 
community, industry, or any other interested parties concerning the 
status of the northern Mexican gartersnake. We are seeking information 
regarding the species' historical and current status and distribution, 
its biology and ecology, ongoing conservation measures for the species 
and its habitat, and threats to the species and its habitat. If you 
wish to comment or provide information, you may submit your comments 
and materials concerning this finding to the Field Supervisor (see 
ADDRESSES section).
    Our practice is to make any comments and materials provided, 
including names and home addresses of respondents, available for public 
review during regular business hours. Respondents may request that we 
withhold a respondent's identity, to the extent allowable by law. If 
you wish us to withhold your name or address, you must state this 
request prominently at the beginning of your submission. 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.

Background

    Section 4(b)(3)(A) of the Endangered Species Act of 1973, as 
amended (16 U.S.C. 1531 et seq.) (Act), requires that we make a finding 
on whether a petition to list, delist, or reclassify a species presents 
substantial scientific or commercial information indicating that the 
petitioned action may be warranted. We are to base this finding on all 
information available to us at the time we make the finding. To the 
maximum extent practicable, we are to make this finding within 90 days 
of our receipt of the petition, and publish our notice of this finding 
promptly in the Federal Register.
    Our standard for substantial information within the Code of Federal 
Regulations (CFR) with regard to a 90-day petition finding is ``that 
amount of

[[Page 316]]

information that would lead a reasonable person to believe that the 
measure proposed in the petition may be warranted'' (50 CFR 424.14(b)). 
If we find that substantial information was presented, we are required 
to promptly commence a review of the status of the species.
    In making this finding, we relied on information provided by the 
petitioners and evaluated that information in accordance with 50 CFR 
424.14(b). Our process of coming to a 90-day finding under section 
4(b)(3)(A) of the Act and Sec.  424.14(b) of our regulations is limited 
to a determination of whether the information in the petition meets the 
``substantial information'' threshold.
    We do not conduct additional research at this point, nor do we 
subject the petition to rigorous critical review. Rather, as the Act 
and regulations contemplate, in coming to a 90-day finding, we accept 
the petitioner's sources and characterizations of the information 
unless we have specific information to the contrary.
    Our finding considers whether the petition states a reasonable case 
for listing the species under the Act on its face. Thus, our finding 
expresses no view as to the ultimate issue of whether the species 
should be listed. We reach a conclusion on that issue only after a more 
thorough review of the status of the species. In that review, which 
will be completed on or by September 15, 2006, we will perform a 
rigorous, critical analysis of the best available scientific and 
commercial information, not just the information in the petition. We 
will ensure that the data used to make our determination as to the 
status of the species is consistent with the Act and Information 
Quality Act (44 U.S.C. 3516).

Petition

    On December 19, 2003, we received a petition dated December 15, 
2003, requesting that we list the northern Mexican gartersnake, 
Thamnophis eques megalops, as threatened or endangered, and that 
critical habitat be designated concurrently with the listing. The 
petition, submitted by the Center for Biological Diversity (hereinafter 
referred to as the petitioners), was clearly identified as a petition 
for a listing rule, and contained the names, signatures, and addresses 
of the requesting parties. Included in the petition was supporting 
information regarding the species' taxonomy and ecology, historical and 
current distribution, present status, and potential causes of decline. 
We acknowledged the receipt of the petition in a letter to Mr. Noah 
Greenwald, dated March 1, 2004. In that letter, we also advised the 
petitioners that, due to funding constraints in fiscal year 2004, we 
would not be able to begin processing the petition in a timely manner.
    On May 17, 2005, the petitioners filed a complaint for declaratory 
and injunctive relief, challenging our failure to issue a 90-day 
finding in response to the petition as required by U.S.C. 1533(b)(3)(A) 
and (B). In a stipulated settlement agreement, we agreed to submit a 
90-day finding to the Federal Register by December 16, 2005, and if 
positive, complete a 12-month finding on or by September 15, 2006 
[Center for Biological Diversity v. Norton, CV-05-341-TUC-CKJ (D. 
Ariz)]. The settlement agreement was signed and adopted by the District 
Court for the District of Arizona on August 22, 2005. This notice 
constitutes our 90-day finding for the petition to list the northern 
Mexican gartersnake as threatened or endangered, pursuant to the 
Court's order.

Biology and Distribution

    The northern Mexican gartersnake may occur with other native 
gartersnake species and can be difficult to identify in the field. The 
northern Mexican gartersnake is a medium-sized member of the family 
Colubridae with a maximum known length of 112 centimeters (cm) [44 
inches (in)]. It ranges in background color from olive to olive-brown 
to olive-gray. Three stripes run the length of the body, with a yellow 
stripe down the back that darkens toward the tail. The pale yellow to 
light-tan lateral stripes distinguish the northern Mexican gartersnake 
from other gartersnake species because a portion of the lateral stripe 
is found on the fourth scale row. Paired black spots extend along the 
dorsolateral fields. A light-colored crescent extends behind the 
corners of the mouth.
    The northern Mexican gartersnake is one of ten subspecies currently 
recognized under Thamnophis eques, has the largest historical 
distribution of these subspecies, and is the only subspecies known to 
occur in the United States. Robert Kennicott first described this 
northern subspecies of Mexican gartersnake in 1860 as Eutenia megalops 
from the type locality of Tucson, Arizona (Rosen and Schwalbe 1988). In 
1951, Dr. Hobart Smith renamed the subspecies with its current 
scientific name of Thamnophis eques megalops (Rosen and Schwalbe 1988). 
A summary of taxonomic history can be found in Rosen and Schwalbe 
(1988).
    The historical distribution of northern Mexican gartersnake in the 
United States was constrained largely to Arizona and, to a lesser 
degree, New Mexico. There have been a number of inventory, monitoring, 
and/or survey efforts in the United States, most of which occurred in 
Arizona (which encompasses the vast majority of the historical 
distribution of northern Mexican gartersnakes in the United States). 
Fewer survey data were found in the literature for Mexico and New 
Mexico. In Arizona, the historical distribution once included the Santa 
Cruz, San Pedro, Colorado, Salt, Agua Fria, Rio Yaqui, and Verde River 
watersheds and presumably the Gila River watershed based on 
historically suitable habitat and geographic proximity to formerly 
extant populations.
    In New Mexico, the northern Mexican gartersnake was once extant in 
the upper Gila River watershed in Grant and Hidalgo Counties. In April 
of 1977, Roger Conant, James S. Jacob, and a group of students counted 
approximately 100 northern Mexican gartersnakes in and around three 
small ponds on private land southwest of Mule Creek Village (Degenhardt 
et al. 1996). This population was considered a stronghold for the 
species in New Mexico (Degenhardt et al. 1996). Charlie Painter, State 
Herpetologist for the New Mexico Department of Game and Fish (NMDGF), 
returned to this location in May 1994 during favorable conditions and 
found only one specimen (C. Painter, pers. comm., New Mexico Department 
of Game and Fish, 2005). This represents a major decline in a 
stronghold population. Mr. Painter stated that he strongly suspects 
that northern Mexican gartersnakes are currently extirpated from New 
Mexico based on several factors including limited historical 
distribution in that State, modification and loss of suitable habitat, 
nonnative species introductions, and the lack of protections offered to 
non-listed, but declining native species on private land (all known 
records of northern Mexican gartersnakes in New Mexico are on private 
land) (C. Painter, pers. comm., New Mexico Department of Game and Fish, 
2005).
    The current distribution of northern Mexican gartersnakes within 
the United States is now generally believed to be limited to four 
geographic areas in Arizona: (1) Middle/upper Verde River--lower Tonto 
Creek; (2) Black River watershed; (3) upper Santa Cruz/San Pedro 
watersheds; and, (4) the San Bernardino National Wildlife Refuge in the 
upper Rio Yaqui watershed (Fitzgerald 1986; Rosen and Schwalbe 1988; 
Arizona Game and Fish

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Department 1996; Rosen et al. 2001; Holycross and Burger 2005).
    The subspecies is also historically known from the Sierra Madre 
Occidental and the Mexican Plateau in the Mexican states of Sonora, 
Chihuahua, Durango, Coahila, Zacatecas, Guanajuato, Nayarit, Hidalgo, 
Jalisco, San Luis Potos[iacute], Aguascalientes, Tlaxacala, Puebla, 
M[eacute]xico, Veracruz, and Quer[eacute]taro (Rossman et al. 1996).
    The northern Mexican gartersnake is considered a native riparian 
obligate (restricted to riparian areas when not engaged in dispersal 
behavior for the purposes of genetic emigration); occurring chiefly in 
the following general habitat types: (1) Source-area wetlands (e.g., 
cienegas (mid-elevation wetlands with highly organic, reducing soils), 
stock tanks (earthen water impoundments), etc.); (2) large river 
riparian woodlands and forests; and (3) streamside gallery forests (as 
defined by well-developed broadleaf deciduous riparian forests with 
limited, if any, herbaceous ground cover or dense grass) (Hendrickson 
and Minckley 1984; Rosen and Schwalbe 1988; Arizona Game and Fish 
Department 2001). Habitat characteristics preferred by the northern 
Mexican gartersnake varies based on the type of habitat. For example, 
in source-area wetlands, dense vegetation consisting of knot grass 
(Paspalum distichum), spikerush (Eleocharis), bulrush (Scirpus), 
cattail (Typha), deergrass (Muhlenbergia), sacaton (Sporobolus), 
Fremont cottonwood (Populus fremontii), Goodding's willow (Salix 
gooddingii), and velvet mesquite (Prosopis velutina) may be preferred 
(Rosen and Schwalbe 1988).
    In small streamside riparian habitat, this snake is often 
associated with Arizona sycamore (Platanus wrightii), sugar leaf maple 
(Acer grandidentatum), velvet ash (Fraxinus velutina), Arizona cypress 
(Cupressus arizonica), Arizona walnut (Juglans major), Arizona alder 
(Alnus oblongifolia), alligator juniper (Juniperus deppeana), Rocky 
Mountain juniper (J. scopulorum), and a number of oak species (Quercus 
spp.) (McCranie and Wilson 1986; Cirett-Galan 1996).
    In riparian woodlands consisting of cottonwood and willow or 
gallery forests of broadleaf and deciduous species along larger rivers, 
the northern Mexican gartersnake may be observed in less dense mixed 
grasses along the bank or in the shallows (Rossman et al. 1996; Rosen 
and Schwalbe 1988). Within and adjacent to the Sierra Madre Occidental 
in Mexico, it occurs in general habitat associations described as 
montane woodland, Chihuahuan desertscrub, mesquite-grassland, and 
Cordillera Volc[aacute]nica montane woodland (McCranie and Wilson 
1987).
    The northern Mexican gartersnake is surface active at ambient 
temperatures ranging from 22[deg] Celsius (C) to 33[deg] C (71[deg] 
Fahrenheit (F) to 91[deg] and forages along the banks of waterbodies 
feeding primarily upon native fish [e.g., Gila topminnow (Poeciliopsis 
occidentalis occidentalis), desert pupfish (Cyrpinodon macularius), 
Gila chub (Gila intermedia), and roundtail chub (Gila robusta)] and 
adult and larval native ranid frogs [e.g., lowland leopard frog (Rana 
yavapaiensis) and Chiricahua leopard frog (Rana chiricahuensis)], but 
may also supplement its diet with earthworms and vertebrates such as 
lizards, small rodents, salamanders, and hylid frogs (treefrogs) (Rosen 
and Schwalbe 1988). An important component of suitable northern Mexican 
gartersnake habitat is an intact native prey base that is not 
significantly affected by nonnative, invasive species (Rosen and 
Schwalbe 1988, 1997; Clarkson and Rorabaugh 1989; Jennings et al. 1992; 
Holm and Lowe 1995; Fernandez and Rosen 1996; Rosen et al. 2001; 
Matthews et al. 2002; Holycross and Burger 2005). However, in some 
populations where the species is present with bullfrogs, adult northern 
Mexican gartersnakes will prey upon juvenile bullfrogs and/or bullfrog 
tadpoles (Holycross and Burger 2005). Juvenile northern Mexican 
gartersnakes may also prey upon nonnative mosquito fish (Gambusia 
affinis) (Holycross and Burger 2005).
    Sexual maturity in male northern Mexican gartersnakes occurs at two 
years of age and at two to three years of age in females. Northern 
Mexican gartersnakes are ovoviviparous (eggs develop and hatch within 
the oviduct of the female). Mating occurs in April and May in their 
northern distribution followed by the live birth of between 7 and 26 
neonates (newly born individuals) (average is 13.6) in July and August 
(Rosen and Schwalbe 1988). Approximately half of the sexually mature 
females within a population reproduce in any one season (Rosen and 
Schwalbe 1988).

Previous Federal Actions

    We placed the northern Mexican gartersnake on the list of candidate 
species as a Category 2 species in 1988 (50 FR 37958). Category 2 
species were those for which existing information indicated that 
listing was possibly appropriate, but for which substantial supporting 
biological data to prepare a proposed rule were lacking. In the 1996 
Candidate Notice of Review (February 28, 1996; 61 FR 7596), the use of 
Category 2 candidates was discontinued, and the northern Mexican 
gartersnake was no longer recognized as a candidate.

Discussion

    We discuss below each of the major assertions made in the petition, 
organized by the listing factors found in section 4(a)(1) of the Act. 
Section 4 of the Act and its implementing regulations found at 50 CFR 
424 set forth the procedures for adding species to the Federal list of 
endangered and threatened species. A species may be determined to be an 
endangered or threatened species if it is threatened by one or more of 
the five factors described in section 4(a)(1) of the Act and meets 
either the definition of endangered or threatened pursuant to section 3 
of the Act. An endangered species is any species which is in danger of 
extinction throughout all or a significant portion of its range. A 
threatened species is any species which is likely to become an 
endangered species within the foreseeable future throughout all or a 
significant portion of its range. The five listing factors are: (1) The 
present or threatened destruction, modification, or curtailment of its 
habitat or range; (2) overutilization for commercial, recreational, 
scientific, or educational purposes; (3) disease or predation; (4) the 
inadequacy of existing regulatory mechanisms; and (5) other natural or 
manmade factors affecting its continued existence. The petitioners 
contend that all five factors are applicable to some degree for the 
northern Mexican gartersnake, as discussed below.
    This 90-day finding is not a status assessment of the northern 
Mexican gartersnake and does not constitute a status review under the 
Act. The discussion presents information provided in the petition 
related to the factors used for evaluation of listing pursuant to 
section 4(a)(1) of the Act for the northern Mexican gartersnake.

A. Present or Threatened Destruction, Modification, or Curtailment of 
the Species' Habitat or Range

Geographic Range and Status
Information Provided in the Petition
    The petitioners claim that northern Mexican gartersnake populations 
in Arizona are in decline and are clearly threatened and reference 
several reports that provide data on survey efforts for the species. 
However, the petitioners' state that information on the northern 
Mexican gartersnakes' population status in New Mexico, and in 
particular, Mexico is less certain but believed to indicate potential 
extirpations or

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declines (Lowe 1985; Stebbins 1985; Rosen et al. 2001; Degenhardt et 
al. 1996; Howland 2000).
    In 2000, Rosen et al. (2001) resurveyed northern Mexican 
gartersnake populations known to be extant during the early to mid 
1980s in southeastern Arizona and included additional information 
collected from 1993 to 2001. Rosen et al. (2001) reported their results 
in terms of increasing, stabilized, or decreasing populations of 
northern Mexican gartersnake. The primary means used to sample the 
herpetofauna included various trapping techniques and field searches. 
Three sites (San Bernardino National Wildlife Refuge, Finley Tank at 
the Audubon Research Ranch near Elgin, and Scotia Canyon in the 
Huachuca Mountains) were intensively surveyed with varied results at 
each site that were discussed by the petitioners and in further detail 
below.
    According to the petitioners, the northern Mexican gartersnake was 
the primary gartersnake species at the San Bernardino National Wildlife 
Refuge from the 1950s through the 1970s. The species is currently 
extirpated or near extirpation in this area based on substantial survey 
effort on the refuge from 1985 to 1989 and again from 1992 to 1999, 
which noted severe declines (Rosen and Schwalbe 1997; Rosen et al. 
2001). Investigators described the decline at the refuge as severe 
because in 1995, 31 northern Mexican gartersnakes were observed on the 
refuge at a standardized capture rate of 0.248 captures/day while in 
1999, one northern Mexican gartersnake was observed with a standardized 
capture rate of 0.002 captures/day; a several-fold decline. The decline 
of the northern Mexican gartersnake on the refuge is largely attributed 
to catastrophic declines and the ultimate extirpation of a primary prey 
species, the Chiricahua leopard frog, a federally threatened species 
(Rosen and Schwalbe 1997; Rosen et al. 2001).
    The petitioners reference Rosen and Schwalbe (1997) which also 
provides a detailed assessment of the status of the northern Mexican 
gartersnake, as well as other aquatic herpetofauna (reptiles and 
amphibians) (including bullfrogs and both Chiricahua and lowland 
leopard frogs) within the San Bernardino National Wildlife Refuge. 
Their work summarizes many projects which commenced in 1985 and focused 
on (1) the impacts of bullfrog invasion on the northern Mexican 
gartersnake; (2) the effectiveness of bullfrog control measures; and 
(3) the effectiveness of leopard frog recovery efforts in the San 
Bernardino Valley. The primary means used to sample the herpetofauna 
included various trapping techniques and field searches.
    Rosen and Schwalbe (1997) noted the northern Mexican gartersnake as 
the primary historical gartersnake species in the San Bernardino 
National Wildlife Refuge, but sampling results in the mid-1980s 
indicated the species as ``unusually uncommon.'' Observations of 
northern Mexican gartersnake populations in 1985 and 1986 in the San 
Bernardino National Wildlife Refuge indicated that recruitment was 
severely hampered due to the significantly limited number of specimens 
observed in the juvenile size classes. The investigators attributed 
this observation to bullfrog predation as most adult specimens captured 
displayed several scars from repeated apparent predation attempts by 
bullfrogs (Rosen and Schwalbe 1997). Bullfrog predation can be 
discerned by such tail-scaring. Native predators generally consume the 
entire animal whereas bullfrogs will often attempt to capture prey 
items larger than they can subdue and physically ingest, which results 
in the scaring observed in northern Mexican gartersnakes on the refuge 
and other areas where they occur with bullfrogs. Similar observations 
were made by Holm and Lowe (1995) in Scotia Canyon, Huachuca Mountains.
    The petitioners reference Rosen and Schwalbe (1997) in stating that 
declines of northern Mexican gartersnakes have been noted in the San 
Bernardino Valley since before formal investigations commenced at the 
San Bernardino National Wildlife Refuge. Cumulative data of gartersnake 
captures (including both the northern Mexican gartersnake and the 
Marcy's checkered gartersnake (Thamnophis marcianus marcianus)) in the 
San Bernardino National Wildlife Refuge indicated a 39 percent decline 
in northern Mexican gartersnake capture rate per unit effort between 
the 1980s and the 1990s. These data were derived from aquatic trapping 
of northern Mexican gartersnake which provided Rosen and Schwalbe 
(1997) with substantial annual samples from 1993 to 1997. Rosen and 
Schwalbe (1997) reasoned this decline could be attributed to natural 
response to persistent drought conditions but that it may have ``masked 
a critical, rapid decline'' in northern Mexican gartersnake populations 
of southeastern Arizona. The qualitative and quantitative data 
generated from the exhaustive research conducted on this species in 
this area clearly confirms the species is nearing extirpation from the 
San Bernardino National Wildlife Refuge, a former stronghold (Rosen and 
Schwalbe 1997; Rosen et al. 2001).
    Surveys at Finley Tank located on the Audubon Research Ranch near 
Elgin, Arizona, that occurred during the period from 1985 to 1988 and 
again in 2000 were cited by petitioners. Chiricahua leopard frogs were 
noted as abundant in the 1985 and 1986 field seasons but have not been 
observed there since 1988. The petitioners cited an observation by Dr. 
Phil Rosen found in Rosen et al. (2001) where he explained, ``At sites 
where leopard frogs are absent, often apparently due to introduced 
centrarchid fish [especially largemouth bass (Micropterus salmoides) 
and green sunfish (Lepomis cyanellus)] as at Babocamari (Cienega), 
northern Mexican garter snakes have become rare prior to the arrival of 
the bullfrog. With only fish to eat, growth is probably markedly 
reduced, and further, at centrarchid sites there are generally few 
small-to medium-sized fish, of edible size for most gartersnakes. In 
that scenario, gartersnake reproduction is likely to be reduced, and 
juvenile growth slowed, as is consistent with the low densities and 
generally smaller snakes seen at the Babocamari.'' The decline of 
native leopard frogs from Finley Tank, possibly exacerbated by the 
effect of recent drought years on the habitat within and around Finley 
Tank, was, according to petitioners, the principle factor which led to 
the precipitous decline in northern Mexican gartersnakes since 1988 at 
this location.
    The last intensively resurveyed area referenced by the petitioners 
and discussed in Rosen et al. (2001) was Scotia Canyon in the Huachuca 
Mountains of southeastern Arizona. A comparison of survey data from 
Holm and Lowe (1995) suggests a possible decline of northern Mexican 
gartersnake populations in this area based on survey data from 1980 to 
1982, with low capture rates in 1993, and even lower capture rates in 
2000. Rosen et al. (2001) noted that bullfrogs were first detected in 
Scotia Canyon in 1989, and by 1992 bullfrogs had overtaken the canyon. 
As referenced in the petition, this bullfrog invasion affected the 
northern Mexican gartersnake age-class distribution in Scotia Canyon to 
one favoring older adults (too large to be eaten by bullfrogs) with 
little, if any, recruitment in the juvenile age-class due to bullfrog 
predation on neonatal and juvenile gartersnakes (Holm and Lowe 1995; 
Rosen et al. 2001). Rosen et al. (2001) commented that the data were 
too sparse to confirm that extirpation of northern Mexican gartersnakes 
from Scotia Canyon was inevitable, but that northern Mexican 
gartersnakes may still

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persist there as a population vulnerable to extirpation.
    The petitioners also reference Holm and Lowe (1995) who also 
conducted a herpetofaunal assessment in Scotia Canyon in 1993, using 
techniques such as active searching during optimal conditions and 
trapping using drift fences (barriers at ground level that direct the 
movements of small vertebrate species into buried containers adjacent 
to the barrier) with minnow traps. The purpose of this assessment was 
to compare the 1993 herpetofaunal community to the 1980 through 1982 
results in the same area. As discussed in Rosen et al. (2001), Holm and 
Lowe (1995) noted bullfrogs to have increased markedly over the time 
between surveys. Native ranid frogs were uncommon during the surveys 
during the early 1980s and were declared locally extirpated from the 
study area in 1993. Of 39 northern Mexican gartersnakes captured in 
1993, 7 were adults, 2 were yearlings, and 30 were young of the year; 
as compared to 6 yearlings and 2 small adults captured in 1980 to 1982. 
Holm and Lowe (1995) suggested such a population structure of northern 
Mexican gartersnakes indicated that while adults are capable of living 
longer and achieving significant size, recruitment is low due to high 
mortality of juvenile snakes from bullfrog predation. Their finding was 
supported by 93 percent of northern Mexican gartersnakes that were 
observed with broken tails likely caused by bullfrog predation attempts 
based upon the predator community in this area (Holm and Lowe 1995).
    Four southeastern Arizona cienega habitats were identified by the 
petitioners as being resurveyed and subsequently discussed in Rosen et 
al. (2001): the Arivaca Cienega, the Babocomari Cienega, Cienega Creek 
at Empire-Cienega Ranch, and Lower Cienega Creek at Cienega Creek 
County Preserve. The Arivaca Cienega was a historical locality for both 
the northern Mexican gartersnake and the Chiricahua leopard frog 
although neither species has been found at this location since 1980 
(Rosen and Schwalbe 1988; Rosen et al. 2001). Arivaca Cienega was 
surveyed on June 13, 1985, and the authors recorded that bullfrogs were 
``extremely abundant'' and grazing pressure was heavy with over 500 
cattle grazing in the habitat (Rosen and Schwalbe 1988). This locality 
was again sampled in 1994 and 2000 with extensive trapping and survey 
effort which yielded a single northern Mexican gartersnake (Rosen et 
al. 2001). Rosen et al. (2001) commented that the northern Mexican 
gartersnake population of the Arivaca Cienega likely succumbed to the 
effects of grazing and a massive bullfrog population, but that the 
single northern Mexican gartersnake found in 2000 indicated the 
``tenacity of a species that long ago apparently became rare in the 
area.''
    A herpetologist surveyed the Babocamari Cienega in June of 1958 and 
noted that northern Mexican gartersnakes, lowland leopard frogs, and 
``southern-form'' (Chiricahua) leopard frogs were extremely abundant 
(Rosen and Schwalbe 1988; Rosen et al. 2001). Some 27 years later in 
1985, research herpetologists again visited this location only to find 
four northern Mexican gartersnakes and no leopard frogs (Rosen et al. 
2001). Surveys that occurred in 2000 did not find either species (Rosen 
et al. 2001). Babocamari Cienega was overtaken by black bullheads 
(Ameiurus melas) and largemouth bass (Micropterus salmoides) between 
the late 1950s and the mid-1980s (Rosen and Schwalbe 1988). Rosen et 
al. (2001) theorize that competition for prey and direct predation from 
nonnative fish were involved in the decline of northern Mexican 
gartersnakes and leopard frogs at Babocamari Cienega.
    The remaining two cienegas identified by the petitioners and 
addressed by Rosen et al. (2001) are both associated with Cienega Creek 
in Santa Cruz and Pima counties of Arizona. The first, a former 
stronghold for northern Mexican gartersnakes, was Cienega Creek at 
Empire-Cienega Ranch which was considered the ``most natural cienega 
remaining in southern Arizona that supports a large and dense 
population of Gila topminnow'' (Rosen et al. 2001). Aquatic habitat 
parameters at this location prevented investigators from setting traps 
per standard protocols, which indirectly placed greater emphasis, and 
less certainty, on hand-collection of northern Mexican gartersnakes. 
Regardless, three adult northern Mexican gartersnakes were captured by 
hand at this location: two in 1986 and one in 2000. While still extant, 
both northern Mexican gartersnakes and leopard frogs have declined 
precipitously from this area and bullfrogs have successfully invaded.
    The last of the cienega habitats that was specifically investigated 
by Rosen et al. (2001) and identified by the petitioners was Lower 
Cienega Creek at Cienega Creek County Preserve. Rosen et al. (2001) 
states that this cienega was historically lush with aquatic and 
emergent vegetation. Overgrazing during the early and mid-1980s denuded 
much of the area's vegetation and resulted in significant erosion 
evidenced by the downcutting of stream banks, in some cases in excess 
of 4.6 meters (15 feet) deep. Lowland leopard frogs have nonetheless 
remained extant through 2001 (Rosen et al. 2001). According to the 
petitioners, the cienega was purchased by Pima County in the 1990s and 
grazing has been prohibited on-site since that time. Subsequent trips 
to this area since the change in ownership have revealed a significant 
improvement in habitat characteristics. By 1998, the first northern 
Mexican gartersnake was observed on the new Cienega Creek preserve and 
has been occasionally observed there since (Rosen et al. 2001). Rosen 
et al. (2001), in acknowledgement of management objectives for this 
area, the potential for habitat regeneration and persistence, and its 
influence on Cienega Creek as a whole, stated that Cienega Creek 
``appears to have the highest potential of any site in the U.S. for 
preservation of the (northern) Mexican gartersnake.''
    According to the surveyors, the many sites in southeastern Arizona 
resurveyed by Rosen et al. (2001) since the 1980s yielded mixed 
results. Populations possibly increased at 1 site (lower Cienega 
Creek), were possibly stable at 2 (lower San Raphael Valley, Arivaca), 
were negative at 14 [Empire-Cienega Creek, Babocomari, Bog Hole, 
O'Donnell Creek, Turkey Creek (Canelo), Post Canyon, Scotia Canyon, 
Lewis Springs (San Pedro River), San Pedro River near Highway 90, 
Barchas Ranch Pond (Huachuca Mountain bajada), Heron Spring, Sharp 
Spring, Elgin-Sonoita windmill well site, and Upper 13 Reservoir (San 
Raphael Valley)], and showed major, demonstrable declines at 2 sites 
(San Bernardino National Wildlife Refuge and Finley Tank). No confirmed 
locality extirpations of northern Mexican gartersnake in southeastern 
Arizona were documented in Rosen et al. (2001).
Habitat
Information Provided in the Petition
    The petitioners state that northern Mexican gartersnake habitat is 
threatened by a variety of factors such as livestock grazing, water 
withdrawal, streambed modification, dams and dam operation, groundwater 
pumping, recreation, mining, encroaching urban development, pollution, 
woodcutting, cultural impacts, and climate change (Hendrickson and 
Minckley 1984; Szaro et al. 1985; Lowe 1985; Rosen and Schwalbe 1988; 
and Rosen et al. 2001). The petitioners did not provide substantial 
information that addresses such threats to northern Mexican gartersnake 
habitat such as woodcutting,

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pollution, cultural impacts, mining, and recreation but cited Lowe 
(1985), which discusses how such activities have led to the 
extirpations of riparian reptile and amphibian populations, and in some 
cases, communities in specific geographic areas.
    The petitioners specifically identify the loss of and continuing 
threats to wetland and cienega habitats and reiterate their importance 
to this particular gartersnake subspecies (Hendrickson and Minckley 
1984; Lowe 1985). Hendrickson and Minckley (1984) state that cienegas 
habitats are an aquatic climax community based on their data review. 
Many of these unique habitats of the southwestern United States, and 
Arizona in particular, have been lost in the past century to streambed 
modification, livestock grazing, cultural impacts, stream flow 
stabilization by upstream dams, channelization, and stream flow 
reduction from groundwater pumping and diversions (Hendrickson and 
Minckley 1984).
    Many sub-basins where cienegas have been severely modified or lost 
entirely overlap, wholly or partially, the historical distribution of 
the northern Mexican gartersnake including the San Simon, Sulphur 
Springs, San Pedro, and Santa Cruz valleys of southeastern and south-
central Arizona. The San Simon Valley possessed several natural cienega 
habitats with ``luxuriant vegetation'' prior to 1885 and was used as a 
watering stop for pioneers, military, and surveying expeditions 
(Hendrickson and Minckley 1984). In the subsequent decades, the 
disappearance of grasses and commencement of severe erosion were the 
result of heavy grazing pressure by large herds of cattle as well as 
the effects from wagon trails that paralleled arroyos, occasionally 
crossed them, and often required stream bank modification (Hendrickson 
and Minckley 1984). Today, only the artificially-maintained San Simon 
Cienega exists in this valley. Similar accounts of past conditions, 
adverse effects from historical anthropogenic activities, and 
subsequent reduction in the extent and quality of cienega habitats in 
the remaining valleys are also provided in Hendrickson and Minckley 
(1984).
    The regional, ecological ramifications of future climate change 
were noted by the petitioners as a significant threat to the northern 
Mexican gartersnake habitat. Specifically, the petitioners restated 
findings discussed in the Final Report of the Southwest Regional 
Climate Change Symposium and Workshop that occurred in September 1997. 
Those findings indicated that the future climate in the American 
southwest may include decreases in summer and winter precipitation and 
an increase of up to 4 [deg]C (7 [deg]F) in average temperature. The 
petitioners claim that such changes in weather patterns and climactic 
conditions will result in more variability in flows that could 
compromise perennial and intermittent streams.
    The petitioners also contend that northern Mexican gartersnake 
populations are vulnerable to local extirpation from the effects of 
livestock grazing within and adjacent to stock tanks, cienegas, and 
riparian areas (Rosen and Schwalbe 1988). Specifically, the loss of 
bank-side vegetation removes an essential habitat component for such 
behaviors as foraging and escaping predation. Once a northern Mexican 
gartersnake population has been extirpated, Rosen and Schwalbe (1988) 
state that unassisted recolonization of extirpated habitat is often 
precluded because it is either isolated between lengthy dewatered 
reaches of intermittent streams or not available to suitable overland 
routes of movement for an aquatic habitat specialist.
    The petitioners cite Rosen and Schwalbe (1988) which provides an 
example of where a known (as of 1983) northern Mexican gartersnake 
population was extirpated in 1984 in Little Ash Creek of the upper Agua 
Fria watershed, potentially due to effects of overgrazing the stream 
banks and emergent vegetation. A survey of the area in April 1984 
produced not a single specimen, and the authors noted severe 
overgrazing that had removed virtually all the cover used by northern 
Mexican gartersnakes in years prior. In August of the following year, 
the area was resurveyed. Rosen and Schwalbe (1988) noted that livestock 
had been removed from the area and that the vegetation had regrown to 
become suitable for northern Mexican gartersnake, yet an intensive 
survey again yielded no specimens.
    The petitioners note that stock tanks used in livestock management 
also experience intentional or unintentional introductions of nonnative 
species of fish, amphibians, and crayfish by anglers and private 
landowners (Rosen et al. 2001). The alteration of habitat, such as 
bank-side vegetation removal and degradation, around stock tanks, may 
also favor nonnative predators as a secondary effect from livestock 
grazing and a threat to northern Mexican gartersnake (Rosen and 
Schwalbe 1988). Alternatively, well-managed stock tanks can provide 
habitat suitable for occupation of the northern Mexican gartersnake, 
both structurally and in terms of its prey base, especially when the 
tank remains devoid of nonnative species while supporting native prey 
species (Rosen and Schwalbe 1988).
    The petitioners discuss how Szaro et al. (1985) assessed the 
effects of grazing on a similar species of gartersnake, the wandering 
(terrestrial) gartersnake (Thamnophis elegans vagrans). The assessment 
compared wandering (terrestrial) gartersnake populations in both grazed 
and ungrazed portions of the same stream. Results indicated that snake 
abundance and biomass were significantly higher in ungrazed habitat 
with a five-fold difference in number of snakes captured, despite the 
difficulties of observing snakes in dense, complex habitat (Szaro et 
al. 1985). Szaro et al. (1985) also noted the importance of riparian 
vegetation in thermoregulation, foraging, and predation-avoidance 
behaviors. The petitioners claim that the northern Mexican gartersnake 
continues to be impacted by on-going livestock operations and provided 
specific reports of adverse effects to northern Mexican gartersnake 
habitat from livestock grazing on public and private lands in 
southeastern Arizona where the species is thought to be extant (Rosen 
et al. 2001).
    Lastly, the historical and potential future effects to northern 
Mexican gartersnake habitat from human population growth and subsequent 
water needs were discussed by the petitioners. Specifically, once-
perennial extensive reaches of historical habitat for the northern 
Mexican gartersnake along the San Pedro and Santa Cruz rivers have been 
lost to the effects of groundwater pumping in response to increasing 
human populations and ensuing urbanization and development within the 
region. The petitioners also express concern for extant populations of 
northern Mexican gartersnake in the Arivaca Cienega and upper Verde 
River because of projected population growth, urbanization, and 
development in those areas and evidence of adverse effects to the water 
supply of these waterbodies due to increasing numbers of regional 
groundwater wells required to support such growth.
Summary of Habitat Threats and Evaluation of Information in the 
Petition
    The petitioners have provided substantial scientific information 
that a variety of anthropogenic activities and other factors that 
affect the habitat of northern Mexican gartersnake.

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B. Overutilization for Commercial, Recreational, Scientific, or 
Educational Purposes

Information Provided in the Petition
    The petitioners state that lawful or unlawful field collecting of 
northern Mexican gartersnakes has not historically been a significant 
threat to the species. However, the petitioners cite that illegal field 
collecting may significantly impact small isolated populations, 
especially if reproductive females are removed from the population 
(Painter 2000). The northern Mexican gartersnake may not be collected 
without special authorization by the AGFD or the NMDGF. Specific 
discussion of the regulatory protections for the northern Mexican 
gartersnake is provided in Section D ``Inadequacy of Existing 
Regulatory Mechanisms'' below.
Evaluation of Information in the Petition
    Since collection of the species is not known to be a major threat, 
the petitioners did not argue that field collection of the species for 
commercial, recreational, scientific, or educational purposes has 
contributed significantly to the current status of the northern Mexican 
gartersnake. However, the petitioners did provide a rational argument 
that small, isolated populations may be particularly vulnerable to 
extirpation from the future illegal collection of reproductive females.

C. Disease and Predation

Information Provided in the Petition and Service Files
    The petitioners acknowledge that disease has not been a direct 
cause for population decline of the northern Mexican gartersnake. Based 
on our information, while disease has not been documented as a specific 
threat to northern Mexican gartersnake in the United States or Mexico, 
disease and nonnative parasites have been implicated in the decline of 
its native prey species. The chytrid fungus outbreak has been 
identified as a chief causative agent in the significant declines of 
many of the native ranid frog species and regional concerns exist for 
the native fish community due to nonnative parasites such as the Asian 
tapeworm (Bothriocephalus achelognathi) in southeastern Arizona (Rosen 
and Schwalbe 1997; Morell 1999; Sredl and Caldwell 2000; Hale 2001; 
Bradley et al. 2002).
    The petitioners discussed the threats from nonnative species 
invasions to northern Mexican gartersnakes' functional prey base. The 
petitioners indicated that riparian communities in Arizona have been 
significantly impacted by a shift in species composition, from being 
historically dominated by native fauna to being increasingly impacted 
by an expanding assemblage of nonnative species (Rosen and Schwalbe 
1988, 1995, 1996, 1997; Holm and Lowe 1995; Degenhardt et al. 1996; 
Fernandez and Rosen 1996; Rosen et al. 2001). The petitioners 
referenced research that suggested that a decline of native prey 
species resulting from the replacement with nonnative species has a 
significant adverse effect on northern Mexican gartersnakes (Rosen and 
Schwalbe 1988, 1995, 1996, 1997; Holm and Lowe 1995; Degenhardt et al. 
1996; Rosen et al. 2001). Subsequently, the status of primary native 
prey species for northern Mexican gartersnake is declining (Rosen and 
Schwalbe 1988, 1995, 1996, 1997; Holm and Lowe 1995; Degenhardt et al. 
1996; Fernandez and Rosen 1996; Rosen et al. 2001).
    The petitioners identified several species as primary prey species 
for the northern Mexican gartersnake that had special Federal or state 
status. For example, the lowland leopard frog has been extirpated from 
New Mexico and from its former distribution in the lower Gila and 
Colorado rivers, and is considered Wildlife of Special Concern by the 
Arizona Game and Fish Department (AGFD). The Chiricahua leopard frog 
was listed as threatened without critical habitat under the Act on June 
13, 2002 (67 FR 40790). The Gila chub was listed as endangered under 
the Act on November 2, 2005 (70 FR 66663). The Gila topminnow was 
listed as endangered under the Act on March 11, 1967 (32 FR 4001). The 
roundtail and headwater chubs were petitioned for listing as threatened 
or endangered under the Act, and we published a substantial 90-day 
finding on the petition for both species on July 12, 2005 (70 FR 39981) 
indicating that the petition provided substantial information for us to 
initiate a status review for the two species. Additionally, the 
roundtail chub is listed as threatened by the State of Arizona. The 
decline of many gartersnake prey species may be tied to predation by 
and competition with nonnative invaders; namely bullfrogs, crayfish, 
and nonnative fish (Rosen and Schwalbe 1988; Holm and Lowe 1995; Rosen 
et al. 2001).
    Petitioners state that the northern Mexican gartersnake is 
particularly vulnerable to a loss in native prey species (Rosen and 
Schwalbe 1988). Rosen et al. (2001) examined this issue in greater 
detail and proposed two plausible explanations: (1) The species is 
reluctant to increase foraging efforts at the risk of increased 
predation; and (2) the species needs substantial food regularly to 
maintain its weight and health. If forced to forage more often for 
smaller prey items, a reduction in growth and reproductive rates may 
likely result (Rosen et al. 2001).
    Direct observations of predation of northern Mexican gartersnake by 
native species are not well documented in the literature; however, 
several species of native fauna opportunistically take other native 
individuals when available (Rosen and Schwalbe 1988). Some examples of 
native predators on the northern Mexican gartersnake may include birds 
of prey, other snakes (kingsnakes (Lampropeltis sp.), whipsnakes 
(Masticophus sp.), etc.), wading birds, raccoons (Procyon lotor), 
skunks (Mephitis sp.), and coyotes (Canus latrans) (Rosen and Schwalbe 
1988). The scientific community does not currently believe these native 
predators are responsible for the historical decline of northern 
Mexican gartersnake as all these species collectively evolved as a 
native biological community.
    Alternatively, the petitioners note that nonnative predation 
threats have been and continue to be a serious factor in the decline of 
the northern Mexican gartersnake from both effects to the species 
itself and to its primary prey base. Many nonnative fishes have been 
introduced into northern Mexican gartersnake habitats, such as 
bullhead, green sunfish, and largemouth bass (Rosen and Schwalbe 1988). 
Rosen et al. (2001) noted the three most damaging nonnative predators 
to the northern Mexican gartersnake and its prey base in southern 
Arizona were bullfrogs, crayfish, and the green sunfish.
    The petitioners claim that, of the various nonnative predators that 
have been introduced to post-settlement Arizona, the bullfrog appears 
to be the most detrimental to the northern Mexican gartersnake (Rosen 
and Schwalbe 1988, 1995, 1996; Holm and Lowe 1995; Rosen et al. 2001). 
Bullfrogs act as competitors to the northern Mexican gartersnake by 
sharing prey items such as frogs, fish, lizards, birds, and even 
mammals (Rosen and Schwalbe 1995). Bullfrogs are particularly damaging 
to and persistent in native riparian communities because adult 
bullfrogs are cannibalistic and larval bullfrogs can be sustained by 
grazing on aquatic vegetation, which means that a population of adult 
bullfrogs can sustain itself even when the native vertebrate prey base 
has been

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extirpated by the species (Rosen and Schwalbe 1995).
    The petitioners referenced documentation that discussed scientists 
and landowners having directly and indirectly observed bullfrogs eating 
northern Mexican gartersnakes in the juvenile and occasionally sub-
adult size classes (Rosen and Schwalbe 1988, 1995, 1996; Holm and Lowe 
1995; Rosen et al. 2001). A well-circulated photograph of an adult 
bullfrog in the process of consuming an adult or subadult northern 
Mexican gartersnake at Parker Canyon Lake, Cochise County, Arizona, 
taken by John Carr in 1964, provides photographic documentation of 
bullfrog predation (Rosen and Schwalbe 1988, 1995). The petitioners 
referenced a common observation in northern Mexican gartersnake 
populations that co-occur with bullfrogs is a preponderance of large, 
mature adult snakes with conspicuously low numbers of individuals in 
the neonate and juvenile age size classes due to bullfrogs eating young 
small snakes, indicating low recruitment (reproduction and survival of 
young) (Rosen and Schwalbe 1988; Holm and Lowe 1995).
    The petitioners contend that bullfrogs that are unable to capture, 
subdue, and consume northern Mexican gartersnakes continue to maintain 
persistent predation pressure on individuals. Signs of attempted 
predation on northern Mexican gartersnakes can be readily observed in 
the field by examining the tail region of individual northern Mexican 
gartersnakes (Holm and Lowe 1995; Rosen and Schwalbe 1996). Rosen and 
Schwalbe (1988) discuss such observations from the San Bernardino 
National Wildlife Refuge where 78 percent of specimens observed had 
broken tails with a ``soft and club-like'' terminus, instead of a long, 
fine point, which suggests repeated injury (multiple predation 
attempts). Rosen and Schwalbe (1988) also noted bleeding from this 
region by gravid females when palpated for egg counts resulting from 
these ``squeeze-type'' of injuries inflicted by adult bullfrogs. Holm 
and Lowe (1995) observed that 89 percent of captured northern Mexican 
gartersnakes possessed similar tail injuries during survey work in 
Scotia Canyon in 1993, indicating heavy predation from abundant 
bullfrogs occurring there as well. These observations made by 
researchers and referenced by the petitioners indicate that, while a 
sub-adult or adult northern Mexican gartersnake may survive an 
individual predation attempt from a bullfrog while incurring tail 
damage, secondary effects from infection of the wound can result in 
mortality of individuals (Rosen et al. 1995). Smaller snakes are 
swallowed whole by bullfrogs.
    The petitioners discuss specific research and field experimentation 
that has been dedicated to understanding the effects of bullfrog 
predation on the northern Mexican gartersnake and its prey base in 
southeastern Arizona, and possible methods for bullfrog eradication 
(Rosen and Schwalbe 1988, 1997; Holm and Lowe 1995; Rosen et al. 2001). 
Specifically, northern Mexican gartersnake and Chiricahua leopard frog 
(prey for the gartersnake) populations were repeatedly surveyed from 
1986 through 1997 at locations on the San Bernardino National Wildlife 
Refuge that suffered from various degrees of bullfrog invasion. Survey 
sites ranged from an entirely native herpetofaunal community to one 
dominated by bullfrogs of various age classes.
    The petitioners reference experimentation with bullfrog removal 
protocols was conducted at various sites on the San Bernardino National 
Wildlife Refuge in addition to a control site with similar habitat on 
the Buenos Aires National Wildlife Refuge with no bullfrog removal 
(Rosen and Schwalbe 1997). Removal protocols employed during this study 
(the extensive removal of adult bullfrogs) resulted in ``remarkable 
blooms'' in younger age-class bullfrogs where removal efforts were 
intensive (Rosen and Schwalbe 1997). Evidence from dissection samples 
of young adult and sub-adult bullfrogs indicated that these age-classes 
readily prey upon younger bullfrogs [4.25 inches (109 mm) snout-vent 
length] as well as juvenile gartersnakes, which suggests that the 
selective removal of large adults (favoring the young adult and sub-
adult age classes) may indirectly lead to increased predation of 
leopard frogs and juvenile gartersnakes (Rosen and Schwalbe 1997). 
Consequently, this strategy was viewed as being potentially ``self-
defeating'' and ``counter-productive'' but worthy of further 
investigation (Rosen and Schwalbe 1997). Both leopard frog and northern 
Mexican gartersnake populations at various locales on the San 
Bernardino National Wildlife Refuge, where bullfrogs have invaded, were 
notably affected by nonnative predation (Rosen and Schwalbe 1997). 
Rosen and Schwalbe (1997) also indicated that northern Mexican 
gartersnakes are precariously close to extirpation from that area.
    The petitioners state that Rosen et al. (2001) concluded that the 
presence and expansion of nonnative predators (mainly bullfrogs, 
crayfish, and green sunfish) continue to be the primary causes of 
decline in northern Mexican gartersnake populations in southeastern 
Arizona due to their deleterious effects to the northern Mexican 
gartersnake and its prey populations. Specifically, Rosen et al. (2001) 
identified the expansion of the bullfrog into the Sonoita Grasslands 
and to the threshold of the Canelo Hills in the upper Santa Cruz River 
watershed, and the expansion of crayfish into Lewis Springs area of the 
upper San Pedro River watershed (these areas comprise one of the 
remaining four, disjunct, geographic areas in the United States where 
the species remains extant), as particularly threatening to the 
northern Mexican gartersnake because these nonnative species have 
proven difficult, if not impossible, to eradicate once established in 
complex, inter-connected habitats as discussed below.
    The petitioners reference Rosen and Schwalbe (1997) who state that 
effective bullfrog and nonnative fish removal is possible in simple 
systems that can be manipulated, such as stock tanks; however, it can 
be expensive and specially-designed fencing is likely needed to prevent 
reinvasion. No methods are available to effectively remove bullfrogs or 
crayfish from lotic (moving water), or complex inter-connected systems. 
The petitioners references indicate that the inability of land managers 
to effectively address the invasion of nonnative species in such 
habitats highlights the particularly serious nature of this specific 
threat. While potential threats from human land use activities can 
usually be lessened or removed completely with adjustments to land 
management practices, the concern for the apparent irreversibility of 
nonnative species invasions becomes paramount.
    While northern Mexican gartersnake populations can be significantly 
affected by bullfrog introductions, the petitioners contend they can 
also be adversely affected by disturbances in the fish community caused 
by nonnative fish introductions (Rosen et al. 2001). The observations 
of the northern Mexican gartersnake populations and individual growth 
trends made by Dr. Rosen at Finley Tank prior to the arrival of the 
exotic bullfrog provides insight on the effects of nonnative fish 
invasions and the potential nutritional ramifications of a fish-only 
diet in a species that normally has a varied diet which is largely 
supported by amphibian prey items (Rosen et al. 2001). The more energy 
that is expended in foraging, coupled by the reduced number of small to 
medium-sized fish available in low

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densities, leads to nutritional deficiencies for both growth and 
reproduction because energy is instead allocated to maintenance and the 
increased energy costs of intense foraging activity (Rosen et al. 
2001).
Evaluation of Information in the Petition
    The petitioners have provided substantial scientific information 
that effects of nonnative predation directly on northern Mexican 
gartersnake and indirectly on its prey base have had negative 
implications for its status and continue to threaten the species.

D. Inadequacy of Existing Regulatory Mechanisms

Information Provided in the Petition
    The petitioners contend that existing regulatory mechanisms, at 
both the State and Federal levels, have failed to cease or reverse the 
decline of the northern Mexican gartersnake. The petitioners identified 
the Service, AGFD, NMDGF, U.S. Forest Service, and the U.S. Bureau of 
Land Management as agencies who share a responsibility to protect the 
northern Mexican gartersnake either via jurisdictional directive or 
through land-management decisions.
    At this time, northern Mexican gartersnake is considered State 
Endangered in New Mexico and take is prohibited without a scientific 
collecting permit issued by the NMDGF as per New Mexico Statutory 
Authority (NMSA) 17-2-41.C and New Mexico Administrative Code (NMAC) 
19.33.6. However, while the NMDGF can issue monetary penalties for 
illegal take, only recommendations are afforded with respect to actions 
that result in destruction or modification of habitat (NMSA 17-2-41.C 
and NMAC 19.33.6).
    In the December 2003 petition, the petitioners state that the AGFD 
allows for the collection of up to four northern Mexican gartersnakes 
per person per year as specified in Commission Order Number 43 (Arizona 
Game and Fish Department 2001). However, according to our information, 
in 2005, the AGFD amended Commission Order Number 43, which closed the 
season on northern Mexican gartersnakes. Take of northern Mexican 
gartersnakes is no longer permitted in Arizona without issuance of a 
scientific collecting permit as per Arizona Administrative Code R12-4-
401 et seq. While the AGFD can seek criminal or civil penalties for 
illegal take of northern Mexican gartersnakes, only recommendations are 
afforded with respect to actions that result in destruction or 
modification of the northern Mexican gartersnakes' habitat. The 
northern Mexican gartersnake is considered a ``Candidate Species'' in 
the AGFD's draft Wildlife of Special Concern in Arizona (WSCA) (Arizona 
Game and Fish Department 1996). A ``Candidate Species'' is one ``whose 
threats are known or suspected but for which substantial population 
declines from historical levels have not been documented (though they 
appear to have occurred)'' (Arizona Game and Fish Department 1996). The 
purpose of the WSCA list is to provide guidance in habitat management 
implemented by land-management agencies. No specific conservation 
actions are mandated or otherwise afforded under this designation. The 
petitioners also claimed that neither agency has mandated recovery 
goals for the northern Mexican gartersnake, nor does either State have 
conservation agreements for this species.
    The petitioners provided an assessment of the northern Mexican 
gartersnakes' legal status in Mexico, all subspecies under Thamnophis 
eques are listed as ``Amenazadas,'' or Threatened, in the species'' 
southern distribution in Mexico by the Secretaria de Medio Ambiente y 
Recursos Naturales (Secretaria de Medio Ambiente y Recursos Naturales 
2003). This legal distinction means that the species is in danger of 
disappearance in the short- or medium-term future from the destruction 
and modification of its habitat and/or from the effects of shrinking 
population sizes (SEMARNAT 2001 [NOM-059-ECOL-2001]). This designation 
prohibits taking of the species, unless specifically permitted, as well 
as activities that intentionally destroy or adversely modify its 
habitat (SEMARNAT 2000 [LGVS] and 2001 [NOM-059-ECOL-2001]). 
Additionally, in 1988, the Mexican Government passed a regulation that 
is similar to the National Environmental Policy Act of the United 
States. This Mexican regulation requires an environmental assessment of 
private or government actions that may affect wildlife and/or their 
habitat (SEMARNAT 1988 [LGEEPA])).
    The U.S. Bureau of Land Management considers the northern Mexican 
gartersnake as a ``Special Status Species'' and agency biologists 
actively attempt to identify gartersnakes incidentally observed during 
fieldwork for their records (L. Young, U.S. Bureau of Land Management, 
pers. comm., 2005). Otherwise, no specific protection or land-
management consideration is afforded to the species on U.S. Bureau of 
Land Management lands.
    The U.S. Forest Service does not include northern Mexican 
gartersnake on their ``Management Indicator Species List'' but it is 
included on the ``Regional Forester's Sensitive Species List''. This 
means that northern Mexican gartersnakes are ``considered'' in land 
management decisions, and individual U.S. Forest Service biologists may 
opportunistically capture and identify the gartersnakes observed 
incidentally in the field for their records, but are not required to do 
so. The petitioners claim that management under the U.S. Forest Service 
does not adequately protect the northe