Endangered and Threatened Wildlife and Plants; Withdrawal of the Proposed Rule To List the Flat-Tailed Horned Lizard as Threatened

DEPARTMENT OF THE INTERIOR

Fish and Wildlife Service

50 CFR Part 17

RIN 1018-AC10

Endangered and Threatened Wildlife and Plants; Withdrawal of the

Proposed Rule To List the Flat-Tailed Horned Lizard as Threatened

AGENCY: Fish and Wildlife Service, Interior.

ACTION: Proposed rule; withdrawal.

-----------------------------------------------------------------------

SUMMARY: The U.S. Fish and Wildlife Service (Service) withdraws the

proposed rule to list the flat-tailed horned lizard (Phrynosoma

mcallii) as threatened, pursuant to the Endangered Species Act of 1973,

as amended (Act). The Service is taking this action because some of the

threats are less serious than at the time the proposed rule was

published, a conservation agreement will ensure further reductions in

threats, and data indicating a population decline are inconclusive. The

Service will continue to monitor the status of this species and work

with involved interests for conservation of the species.

ADDRESSES: The complete file for this rule is available for inspection,

by appointment, during normal business hours at the Carlsbad Ecological

Services Field Office, U.S. Fish and Wildlife Service, 2730 Loker

Avenue West, Carlsbad, California, 92008.

FOR FURTHER INFORMATION CONTACT: Sandy Vissman, at the above address or

by telephone at (760) 431-9440.

SUPPLEMENTARY INFORMATION:

Background

The flat-tailed horned lizard (Phrynosoma mcallii) is a small,

cryptically colored, phrynosomatid lizard that reaches a maximum adult

body length (excluding the tail) of approximately 81 millimeters (3.2

inches). The lizard has a flattened body, short tail, and dagger-like

head spines like other horned lizards. It is distinguished from other

horned lizards in its range by a dark vertebral stripe, two slender

elongated occipital spines, and the absence of external ear openings.

The dorsal surface of the flat-tailed horned lizard is pale gray to

light rusty brown. The ventral surface is white and unmarked, with the

exception of a prominent umbilical scar.

The lizard was first collected by Colonel G.A. M'Call, between Camp

Yuma and Vallecito in the 1850s. Through the mid-1900s, most locality

information came from California, where it became apparent that the

flat-tailed horned lizard occupied the lower elevations of the Salton

Trough in Riverside, Imperial, and San Diego Counties. Because of

distinctive morphological characteristics, Hallowell (1852) first

described the species as Anota M'callii, placing the flat-tailed horned

lizard in a monotypic genus. The flat-tailed horned lizard remained a

subject of taxonomic controversy for many years, occupying subsequently

the genus Doliosaurus (Girard 1858), Phrynosoma (Cope 1866), and Anota

(Cope 1900). Taxonomic questions were finally resolved by Norris and

Lowe (1951), who determined that the similarities of this species to

other horned lizards were more significant than its differences and

placed the

[[Page 37853]]

species again in Phrynosoma. No subsequent change in the taxonomic

status has been proposed for P. mcallii, other than clarification by

Funk (1981) of the spelling of the specific epithet. The flat-tailed

horned lizard is one of the more distinctive of the 13 species

currently recognized in the genus.

The flat-tailed horned lizard is endemic to the Sonoran Desert in

the Coachella Valley in Riverside County, California; the Imperial and

Borrego valleys in and near Anza Borrego and Ocotillo Wells in Imperial

and eastern San Diego counties, California; south of the Gila River and

west of the Gila and Tinajas Altas mountains in Yuma County, Arizona;

east of the Sierra de Juarez in the Laguna Salada and Yreka Basins in

northeastern Baja California Norte, Mexico; and north and west of Bahia

de San Jorge to the delta of the Rio Colorado in northwestern Sonora,

Mexico (Turner and Medica, 1982). The species occurs at elevations up

to 800 meters (2600 feet) above sea level, but most populations are

below 300 meters (980 feet) elevation. Within this range, the flat-

tailed horned lizard typically occupies sparsely vegetated, sandy

desert flatlands with low species diversity, but it is also found in

areas covered with small pebbles or desert pavement, mud hills, dunes,

alkali flats, and low, rocky mountains. According to Hodges (1997),

approximately 51.2 percent of the historic range of the flat-tailed

horned lizard habitat within the United States is extant. An estimated

maximum of 503,500 hectares (ha) (1,244,000 acres (ac)) of habitat

remains in the United States, with approximately 56,800 ha (140,300 ac)

found in Arizona and 446,670 ha (1,103,800 ac) found in California.

Johnson and Spicer (1985) estimated that approximately 29 percent

of the species' range occurs in Mexico; however, the distribution of

the species in Mexico is poorly understood because of the lack of

distribution inventories for the species. The acreage of suitable

habitat found within the estimated range in Mexico is unknown. The

species' distribution in Baja California Norte is limited by extensive

agriculture that extends from Mexicali to the Colorado River and by the

wetland and riparian communities of the Colorado River Delta, the Rio

Hardy, and Laguna Salada. In Sonora, records indicate flat-tailed

horned lizards exist primarily from an extensive sandy plain east of

the Colorado River to the dunes of the Gran Desierto and also near

Puerto Penasco. Between these areas is a relatively undisturbed region

dominated by the large dune system of the Gran Desierto and volcanic or

montane terrain in the Sierra Pinacate region, an area where few

locality records exist and potential flat-tailed horned lizard habitat

appears scattered (Gonzales-Romero and Alvarez-Cardenas 1989).

Vegetation throughout the range of the flat-tailed horned lizard is

predominantly Sonoran Desertscrub (Turner and Brown 1982). Flat-tailed

horned lizards are found in habitat types including desert pavement,

pebbled areas, mudhills, and dune edges. Characteristics of ``high

quality'' flat-tailed horned lizard habitat include sparse vegetation,

little slope, and surface soils of fine, packed sand or desert pavement

overlaid intermittently with loose, fine sand (Turner et al. 1980). In

Ocotillo Wells, however, recent work has found higher abundances of

lizards in mudhills than in sandy areas (Wone 1997). The relationship

between vegetation density and lizard abundance is unclear because of

differences between study results. Wone (1996) found a negative

correlation between lizard abundance and vegetation density, while

Turner and Medica (1982) found a positive correlation between lizard

abundance and perennial density. Altman et al. (1980) stated that when

aggregate perennial densities are less than 250 per ha, ``the habitat

is not likely to be favorable for P. mcallii. Almost all areas examined

with high abundance of mcallii had aggregate perennial densities of

greater than 1000/ha.''

Because of difficulties in locating flat-tailed horned lizards,

Turner et al. (1980) used scat counts to estimate the relative

abundance of the species throughout its range. Broadly defined areas

with high relative abundance of flat-tailed horned lizards have been

found in California and Arizona using these methods and historical

locality records. Turner and Medica (1982) identified four such areas

in California, including southern East Mesa, southeastern Yuha Desert,

the Superstition Mountain area in Imperial County, and the Benson Dry

Lake area near Ocotillo Wells in San Diego County. Rorabaugh et al.

(1987) identified one area of high relative abundance southeast of Yuma

in Yuma County, Arizona. Although Muth and Fisher (1992) caution

``habitat quality should not be inferred from scat counts,'' historical

locality records support the assessment of habitat quality in the

aforementioned areas.

Rough estimates of flat-tailed horned lizard density have been made

in different parts of the species' range. Estimated densities include

0.3-1.5 lizards/ha (Rorabaugh 1994), 0.6 lizards/ha (Hodges 1995), 4.8-

8.4 lizards/ha (Turner and Medica 1982), and 1.3-1.39 lizard/ha (Muth

and Fisher 1992). Rorabaugh (1994) recalculated the data presented by

Turner and Medica (1982) using different analytical techniques, and

arrived at a maximum density of 3.8/ha. Differences between studies in

estimated density may represent differences in the lizard abundance in

areas studied, differences in lizard abundance attributable to general

declines in the species' abundance over the years between studies, or

differences due to different methods of data collection and analysis.

Approximately 503,500 ha (1,244,000 ac) of flat-tailed horned lizard

habitat remain in the United States (derived from Hodges 1997), with

approximately 176,800 ha (437,000 ac) of that habitat located within

areas designated by Federal agencies as Flat-tailed Horned Lizard

Management Areas (MAs) (Foreman 1997). Based on the density range (0.3-

3.8 lizards/ha) and habitat acreage estimates presented above, the

population of lizards protected within MAs could range from 53,056 to

672,045. These are rough estimates because habitat quality varies

throughout MAs, some surface disturbance currently exists within the

management areas, flat-tailed horned lizards are not evenly distributed

across their range, and the large difference between the two density

estimates is not accounted for in the literature. Even a population of

a size at the low end of this range is large enough that it is not

likely to be threatened by demographic and genetic factors.

A Flat-tailed Horned Lizard Population Viability Analysis (PVA) was

conducted by a Conservation Team convened to share research involving

this species and to evaluate a proposed management strategy. The final

PVA provided no estimate of the minimum viable population size and did

not determine whether populations contained within the proposed

management areas were viable. The Conservation Team concluded that

further information was necessary to extrapolate from a PVA, but

identified variables that apparently have a large effect on population

viability. When introduced into modeled populations, variations in

mortality, fecundity, number of egg clutches produced by a female in a

year, and environmental conditions strongly affect population

viability.

In June, 1997, Federal and State agencies signed a Flat-tailed

Horned Lizard Conservation Agreement (CA) and agreed to implement a

Flat-tailed Horned Lizard Rangewide Management Strategy (Management

Strategy). The

[[Page 37854]]

Management Strategy was developed by an interagency working group over

a two-year period. As part of the CA, agencies delineated specified

acreages under their jurisdiction as MAs. Approximately 176,800 ha

(437,000 ac) of the remaining flat-tailed horned lizard habitat is

found within MAs. This acreage represents approximately 35 percent of

habitat remaining in the United States. Signatories of the CA, which

include the Service, Bureau of Land Management (BLM), Bureau of

Reclamation (BoR), U.S. Marine Corps, U.S. Navy, Arizona Game and Fish

Department, and California Department of Parks and Recreation,

committed to implementation of conservation measures for the species.

These measures include: continuation of monitoring of lizard

populations and new surface disturbance within MAs; limitation of

surface-disturbing projects within MAs to one percent of the area of

MAs over the course of the next five years; collection of compensation

fees from project proponents conducting activities within MAs;

reduction in off-highway vehicle (OHV) routes within MAs; prohibition

of off-highway competitive events within MAs; support of continued

flat-tailed horned lizard monitoring and research; mitigation for

surface disturbing activities in lizard habitat; and attempting to

acquire all private inholdings within MAs. Participation in the CA/

Management Strategy is voluntary, and agencies may withdraw from

participation with 60 days notice.

Prior to signing the agreement, agencies had already begun to

implement planning actions identified as part of this agreement,

including designation of MAs on BLM lands in California, application of

mitigation measures on surface-disturbing projects on BLM lands in

California, requiring compensation from project proponents conducting

surface-disturbing activities in flat-tailed horned lizard habitat,

designation of OHV routes on BLM lands in California (Foreman 1997),

and acquisition of inholdings within the Yuma MA. Many of the measures

identified in the CA are part of the agencies' ongoing management

strategies and have been in place for years. Furthermore, the U.S.

Marine Corps, at the Barry Goldwater Range in Arizona, has agreed to

implement the terms and conditions of a conference opinion on ongoing

activities, regardless of the species' status under the Act. Terms and

conditions of the conference opinion include: limiting surface

disturbance, enforcement of ``no trespass'' rules on the range, and

initiation of a speed limit of 25 miles per hour on roads found within

the range (U.S. Fish and Wildlife Service 1996). A Management Oversight

Group, composed of managers from CA signatory agencies, was established

to oversee implementation of the Management Strategy. This group first

met on June 26, 1997.

Previous Federal Action

The Service included the flat-tailed horned lizard as a category 2

candidate for listing in its original Review of Vertebrate Wildlife,

published in the Federal Register on December 30, 1982 (47 FR 58454).

Category 2 candidates were those species for which data in the

Service's possession indicated listing may be appropriate, but for

which additional biological information was needed to support a

proposed rule. This species was again included as a category 2

candidate in the Service's revised Vertebrate Notice of Review of

September 18, 1985 (50 CFR 37958). Subsequently, the status of the

flat-tailed horned lizard was elevated to category 1 on January 6, 1989

(54 FR 554), as new data on this species became available (Carlson and

Mayhew 1988; Olech, undated; Rorabaugh et al. 1987). Category 1

candidates were those species for which the Service had on file

sufficient information to support issuance of proposed listing rules.

On November 29, 1993, the Service published a proposal (58 FR 62624) to

list the flat-tailed horned lizard as a threatened species.

The Service held a public hearing on March 22, 1994, in Imperial,

California, in response to formal requests from the public (59 FR

8450). The public comment period on the proposed rule was reopened from

February 22, 1994, until April 22, 1994. At that time, the Service was

unable to make a final listing determination on this species because of

higher listing priorities.

On April 10, 1995, Congress enacted a moratorium on listing actions

(Public Law 104-6) and eliminated funding for the Service to conduct

final listing actions. The moratorium was lifted on April 26, 1996, by

means of a Presidential waiver, at which time limited funding for

listing actions was made available through the Omnibus Budget

Reconciliation Act of 1996 (Pub. L. No. 104-134, 100 Stat. 1321, 1996).

The Service published listing priority guidance for restarting the

listing program on May 16, 1996 (61 FR 24722). When funding was

restored, the Service commenced work on final actions, including the

flat-tailed horned lizard proposed listing, in accordance with the

listing priority guidance. The Service also coordinated with involved

agencies on additional alternatives for conservation of the species.

The BLM opened a public comment period on the draft Management

Strategy from January 21, 1997, to March 19, 1997 (62 FR 3052). The

Management Strategy was the product of numerous meetings between

agencies and individuals with an interest in the flat-tailed horned

lizard. Public meetings regarding the draft Management Strategy were

held in El Centro, California, on February 19, 1997, and in Yuma,

Arizona, on February 20, 1997. Comments were addressed by the BLM, and,

on June 9, 1997, Federal and State agencies signed a CA to implement

the Management Strategy.

On March 5, 1997, the proposed rule comment period was reopened due

to the time that had elapsed since the close of the initial comment

period, changing procedural and biological circumstances, and the need

to review the best scientific information available (62 FR 10016). The

comment period was again extended for 30 days on May 6, 1997 (62 FR

24632).

On May 8, 1997, in response to a lawsuit filed by the Defenders of

Wildlife, a U.S. District Court for the District of Arizona ruled that

the Service must make a final determination on whether to list the

flat-tailed horned lizard within 60 days of the filing date of the

court order (May 16, 1997).

The processing of this proposed rule conforms with the Service's

final listing priority guidance published in the Federal Register on

December 5, 1996 (61 FR 64475). The guidance clarifies the order in

which the Service will process rulemakings during fiscal year 1997. The

guidance calls for giving highest priority (Tier 1) to handling

emergency situations, second priority (Tier 2) to resolving the listing

status of the outstanding proposed listings, and third priority (Tier

3) to new proposals to add species to the lists of threatened and

endangered plants and animals. Processing of this proposed rule

constitutes a Tier 2 action.

Public Comments on the Proposed Rule

In the November 29, 1993, proposed rule (58 FR 62624) and

associated notifications, all interested parties were asked to submit

factual reports or information that might contribute to development of

a final rule. Appropriate State agencies and representatives,

scientific organizations, and other interested parties were contacted

and requested to comment. A public hearing was held on March 22, 1994,

at Imperial Valley College at which 11 individuals

[[Page 37855]]

testified. To allow for adequate public comment, the Service had four

comment periods: November 29, 1993, to January 28, 1994 (58 FR 62624);

February 22 to April 22, 1994 (59 FR 8450); March 5 to May 9, 1997 (62

FR 10016); and May 9 to June 9, 1997 (62 FR 24632).

During the comment periods, the Service received a total of 59

comments (oral and written testimony) including 39 comments in support

of Federal listing, 17 in opposition to Federal listing, and 2 neutral

comments. Opposition to the listing proposal was expressed by two State

agencies, two Federal agencies, five municipalities or municipal

agencies, and eight other interested parties. Support for the listing

was expressed by 1 Federal agency and 38 other interested parties.

The proposed rule to list this species pre-dated the Service's

policy to seek independent peer review (59 FR 34270). However, during

the open comment periods, the Service solicited the expert opinions of

appropriate independent specialists regarding pertinent scientific or

commercial data and assumptions relating to the taxonomy and biological

and ecological information for the flat-tailed horned lizard. The

comments received were considered in making the Service's determination

on the proposed rule.

Written comments and oral statements obtained during the public

hearing are incorporated into this withdrawal notice where appropriate.

The Service carefully considered all comments submitted relevant to the

decision to finalize or withdraw the proposed listing. Comments

submitted are available for review at the Service's Carlsbad Ecological

Services Office (see ADDRESSES section). Because it now withdraws the

proposal to list the flat-tailed horned lizard, the Service will

respond to issues raised in comments that supported listing. Seven

relevant issues were raised in these comments, and the Service's

response to each is as follows:

Issue 1: Data on flat-tailed horned lizard population trends are

unclear.

Service Response: Quantification of flat-tailed horned lizard

abundance is difficult due to the sedentary nature, cryptic coloration,

and patchy distribution of this species. Turner et al. (1980) developed

a survey technique to estimate the relative abundance of flat-tailed

horned lizards based on counts of the number of scats observed per

observer per hour. The technique, modified by Olech (undated), assumes

the number of flat-tailed horned lizards is directly proportional to

the number of scats and uses both the number of scats and number of

lizards observed to estimate the relative lizard abundance. Surveys

were conducted in 1979, 1981, 1984-1991, and 1993-1996 using this

technique. The survey results have been used to estimate large-scale

population trends (Wright 1993). Recently, the validity of this

methodology has been reexamined (Wone 1997; Muth, in litt. 1997; Wright

1993). The methodology does not account for variations in lizard

activity, scat production due to fluctuating food resources, weather

conditions that affect scat production or longevity in the field,

observer capability, or small sample sizes (Rorabaugh 1994). Changes in

scat abundance over time could be caused by changes in lizard activity

or scat production rather than changes in population size. The

Department of Defense (DoD) has recently funded work to assess the

validity of using scat counts to determine relative abundance and to

develop an improved survey technique. In the interim, a modified scat

count method, still considered the best available technique, continues

to be used to estimate population trends on BLM lands in California,

and, in conjunction with habitat parameters and locality records, to

determine presence or absence of the species.

The relationship between scat counts and lizard abundance is

unclear. Scat counts may provide a rough index for assessing relative

abundance (Rorabaugh 1994), but Wone (1997) found that scat counts were

not correlated to relative abundance at Ocotillo Wells in California.

However, Wright (1993) found that scat counts were correlated with

numbers of lizards encountered during scat surveys. Muth and Fisher

(1992) concluded that scat counts should be used only to determine

relative abundance, but not to estimate population size or habitat

quality. Some researchers feel that scat counts consistently

overestimate the number of flat-tailed horned lizards because other

lizard species can produce scat similar in size (Muth, in litt. 1997).

The information on population trends presented in the proposed rule

was derived from scat count data collected between 1979 and 1991.

Although the best information currently available on relative abundance

and population trends of flat-tailed horned lizards is derived from

scat counts, the confounding effects of scat persistence, heterogeneous

scat distribution, variable rates of scat production, variations in

survey methodology over time, and drought, including localized effects

of low rainfall in different parts of the desert, make the population

trend information derived from scat counts inconclusive. The population

trends presented in the proposed rule showed that, between 1979 and

1991, two areas, West Mesa and East Mesa, did not experience a

significant downward population trend and one area, the Yuha Desert,

experienced an overall downward population trend. However, later

analyses performed subsequent to publication of the proposed rule show

that the Yuha Desert experienced an upward trend between 1991 and 1993

(Wright 1993) and no trend between 1993 and 1995 (Nicolai, unpublished

data). The apparent downward population trend in the Yuha Desert noted

in the proposed rule occurred in, and subsequent to, years

characterized by drought. The observed downward trend may have been due

to a temporary population decline or reduced scat production due to

drought and reduction of food resources, rather than long-term habitat

deterioration. In the short term, if flat-tailed horned lizards have

less food resources available during drought years, a stable population

may produce less scat as lizards become less active; this could cause

erroneous population trend results (Rorabaugh 1994). Longer term

declines in scat production during drought periods may be indicative of

population reductions due to decreased reproduction or increased

mortality.

Other information on population trends is largely anecdotal. Turner

et al. (1980) reported few flat-tailed horned lizards and low scat

counts on and near Highway 78 in East Mesa, California, an area where

the species was one of the most abundant lizard species in the 1960s

(Carlson and Mayhew 1988). Norris (1949) believed the species was

fairly common in the Coachella Valley where flat-tailed horned lizards

are now difficult to find (Turner et al. 1980). Neither these

observations nor trend data derived from scat counts are sufficient to

conclude that the species' population is significantly declining in

areas of extant habitat.

Issue 2: Numerous comments supporting the proposal to list the

flat-tailed horned lizard reiterate threats identified in the proposed

rule, or identify new threats facing this species in portions of its

range. Threats identified in comments include: current and projected

habitat loss due to authorized and unauthorized off-highway vehicle

activity; geothermal development; sand and gravel extraction; road

construction; oil and gas leasing; powerline construction; canal or

pipeline construction; Border Patrol off-road activity; lack of

regulatory mechanisms (including unsuccessful BLM efforts to protect

[[Page 37856]]

species); residential, recreational, and industrial development;

agriculture and resulting chemical pollution; land conversion on BLM

inholdings authorized through the Imperial County General Plan;

activities on lands adjacent to habitat; expansion of exotic plants

into lizard habitat; increased fire frequency due to exotic plant

expansion; and predation.

Service Response: The threats to the flat-tailed horned lizard are

addressed in detail in the ``Summary of Factors Affecting the Species''

section of this notice. Based on analyses conducted prior to the

proposal to list the flat-tailed horned lizard, as well as from more

recent analyses, an estimated 30-51 percent of historical flat-tailed

horned lizard habitat in the United States was modified or destroyed in

the past century. However, the extent of current rangewide threats

facing remaining flat-tailed horned lizard populations is less clear.

Although individual populations are threatened by residential,

recreational, industrial, and agricultural development, large tracts of

suitable habitat remain relatively undisturbed in Mexico and on public

lands in the United States. Habitat found on public lands is protected

to varying degrees by existing land-use designation. Significant

potential threats to this species on public lands have been reduced or

eliminated since publication of the proposed rule to list the species

as threatened.

Issue 3: Several commenters stated that the BLM in California has

failed to implement planned actions in previous conservation plans and

questioned the ability of the BLM in California to manage habitat for

this species or to accomplish the goals established in the CA and

Management Strategy.

Service Response: The BLM has renewed and strengthened its

commitment to the conservation of the flat-tailed horned lizard through

participation in the development of the Management Strategy and

subsequent signing of the CA. The Service anticipates that the BLM will

implement the Management Strategy; however, the decision to withdraw

the proposal to list the flat-tailed horned lizard is not based solely

on BLM participation in the CA and Management Strategy. The flat-tailed

horned lizard occurs not only on the BLM lands in California, but also

on lands owned by the DoD, BoR, U.S. Marine Corps, U.S. Navy, BLM in

Arizona, and California Department of Parks and Recreation. All of

these agencies are signatories to the CA. The Service will continue to

monitor the implementation of proposed actions through participation in

the Interagency Coordinating Committee (ICC), and the Management

Oversight Group designated in the CA. The BLM has demonstrated its

commitment to implementation of the CA by already taking actions

identified in the Management Strategy. Planning actions that are being

implemented by BLM in California include: designation of MAs;

application of mitigation measures to surface disturbing activities;

collection of compensation fees for unavoidable habitat alteration due

to surface disturbing activities; seeking acquisition of private

inholdings within MAs; limitation of habitat disturbance within MAs to

one percent; coordinating with the Border Patrol; initiation of OHV

route designation and signing; and prohibiting insecticide treatments

within MAs as outlined in the BLM Record of Decision for the Curlytop

Virus Control Program.

Issue 4: Proposed and anticipated development on public and private

lands facilitated by the North American Free Trade Agreement (NAFTA)

threatens flat-tailed horned lizard populations and potential habitat

in the United States and Mexico.

Service Response: Development due to NAFTA is likely to impact some

flat-tailed horned lizard populations and some habitat in the United

States and Mexico. However, the area likely to experience such

disturbance is not adequately documented and the significance of this

threat to the species as a whole can not be determined based on the

limited available information.

Issue 5: Off-highway vehicle activities pose continued threats to

habitat throughout much of flat-tailed horned lizard range.

Service Response: While OHV activity poses a potential local threat

to the flat-tailed horned lizard, there is no documentation that OHV

use poses a significant threat throughout the range of the species.

Off-highway vehicles are known to cause lizard mortality and habitat

disturbance (Muth and Fisher 1992, Rado 1981). The level of OHV

activity, however, varies from a high level within OHV open areas to a

low level in areas where existing routes are located miles apart. The

zone impacted by established routes and the resulting impact on local

lizard populations have not been determined.

Although some studies found reduced scat abundance where vehicular

tracks were abundant (Olech undated), studies that have attempted to

assess impacts of OHV activity on flat-tailed horned lizards have been

inconclusive. For example, Klinger et al. (1990) were not able to

assess the effects of varying levels of OHV activity because the

different levels of OHV activity which they examined occurred in

different habitat types. In a small number of study plots (n=6) at the

Imperial Sand Dunes (ISD) in southeastern California, Bury and

Luckenbach (1983) found that areas impacted by OHV activity exhibited

lower abundances of rodents, lizards, and plants than areas where there

was no OHV activity. However, in plots of different levels of OHV

activity, Wone et al. (1990) and Wright (1993) found no difference in

the abundance of flat-tailed horned lizard scat. Some OHV activity

causing habitat disturbance is unauthorized, but information concerning

the amount and impact of unauthorized OHV activity is unavailable.

Although OHV activity results in lizard mortality and habitat

disturbance, there is no evidence, based on current data, that this

activity is a significant threat to the species or is resulting in

rangewide declines of flat-tailed horned lizard populations.

Issue 6: Several commenters noted that there are research gaps

involving the flat-tailed horned lizard that need to be better

understood to develop conservation measures. Needs include researching

lizard movements, ecology, recolonization potential, and nesting sites

and studying the effects of OHVs on the species.

Service Response: The Service agrees that a better understanding of

a variety of aspects of flat-tailed horned lizard ecology, such as

movement, habitat use, recolonization potential, age-specific

survivorship, reproductive ecology, demographics, population viability,

and effects of OHVs on the species, is necessary to develop proper

conservation measures, and to better assess the status of the species.

Issue 7: Several commenters who support listing the flat-tailed

horned lizard as threatened question the ability of the CA and

Management Strategy to sufficiently protect the flat-tailed horned

lizard. Issues raised surrounding the CA include: enforceability of the

CA, funding of the CA, the ability of the CA to remove threats,

unprotected status of private inholdings found within the MAs and the

Management Strategy's allowance of continued fragmentation.

Service Response: The Service anticipates that continued

implementation of the CA and Management Strategy will provide continued

protection for this species on substantial acreages contained within

MAs. The signatory agencies have begun implementation of actions

identified within the Management Strategy and

[[Page 37857]]

have agreed to monitor surface disturbance and population trends, given

the best available methodology, and report each on an annual basis to

the Management Oversight Group. Furthermore, agencies have agreed to

seek acquisition of all private inholdings within the boundaries of

MAs. To date, private inholdings within the boundaries of MAs total

approximately 19,280 ha (48,200 ac) (Foreman 1996). The BLM has

informed the Service that it has issued a Notice of Proposed Exchange

and is developing a Draft Environmental Assessment for a land exchange

process whereby BLM acreage located outside of priority areas will be

exchanged for private inholdings within BLM MAs. Priorities for

inholding acquisition via this exchange include private inholdings

found within Wilderness Areas, critical habitat designated for

federally listed species, and Areas of Critical Environmental Concern

(ACECs). The Marine Corps is in the process of acquiring all state

lands found within the boundaries of the MA which lie within the Barry

M. Goldwater Range. Funding is currently being sought by the Management

Oversight Group for further implementation of the strategy. The

Management Strategy focuses on five MAs that are disjunct, and it is

the objective of the Management Strategy to provide enough protected

area within each MA to sustain a viable population within each MA.

It should be noted that, while the CA and Management Strategy are

important tools in the conservation of the flat-tailed horned lizard,

withdrawal of the proposal to list this species as threatened is not

based solely on the CA and Management Strategy. Threats identified in

the proposed rule have been reduced or eliminated since the publication

of the proposed rule, and the information regarding population trends

is inconclusive. The Management Strategy will, however, provide for

conservation of the flat-tailed horned lizard on the extensive public

lands on which it occurs and facilitate continued evaluation of the

status of this species. The Service believes that the Management

Strategy has and will continue to benefit flat-tailed horned lizard

populations by significantly reducing the threats on public lands.

Summary of Factors Affecting the Species

The Service must consider five factors described in section 4(a)(1)

of the Act when determining whether to list a species. These factors,

and their application to the Service's decision to withdraw the

proposal to list the flat-tailed horned lizard, are as follows:

A. The Present or Threatened Destruction, Modification, or Curtailment

of Its Habitat or Range

Habitat loss has occurred throughout the range of the flat-tailed

horned lizard. The proposed rule stated that approximately 34 percent

of the historical habitat had been lost (23-27 percent in Arizona, and

40 percent in California). According to Hodges (1997), using different

methodologies from those used in the proposed rule, approximately 48.6

percent of the historical range in the United States (31.1 percent in

Arizona, and 50.2 percent in California) has been lost due to four

primary activities; agriculture, filling the Salton Sea, urbanization,

and military activities. Hodges (1997) analyzed the boundaries for the

historical range, as well as the approximate total acreage of habitat

remaining for this species. She estimates a maximum of 56,800 ha

(140,300 ac) of habitat remain in Arizona, and, based on estimates of

historical habitat and habitat loss, approximately 446,900 ha

(1,103,800 ac) of habitat remain in California.

The proposal to list the flat-tailed horned lizard as threatened,

and comments received during the public comment period, identified

human activities that have modified or were anticipated to modify the

habitat. Activities that have disturbed habitat within the range of the

flat-tailed horned lizard include: geothermal development; residential,

recreational, and industrial development; agricultural conversion and

resulting chemical pollution; sand and gravel extraction, oil and gas

leasing; canal, pipeline, and transmission line construction; and

authorized and unauthorized OHV activity.

Loss of flat-tailed horned lizard habitat due to geothermal

development historically has occurred on both private lands and BLM

lands east of El Centro, California. Geothermal resources are known to

occur in this area as part of the Known Geothermal Resource Area

(KGRA). Historically, approximately 28,240 ha (69,760 ac) of potential

flat-tailed horned lizard habitat were subject to geothermal

development due to construction, maintenance and operation of

geothermal powerplants within the KGRA. Because energy extraction

technology within East Mesa has proven technologically unfeasible, and

government subsidies have begun to expire, no new geothermal

powerplants are proposed at this time (Larry Caffee, pers. comm. 1997).

Consequently, future geothermal power plant construction and resulting

habitat loss are not anticipated at this time.

In the early 1980s, acreage throughout California was leased to oil

and gas companies. Approximately 7,800 ha (19,200 ac) were estimated to

be subject to oil and gas exploration and development based on pending

oil and gas leases in 1980 (Rado 1981). This information was utilized

in the proposed rule to list the flat-tailed horned lizard. Since the

publication of the proposed rule, all oil and gas leases within the

range of the flat-tailed horned lizard have expired (BLM 1996), and are

not anticipated for renewal because of low likelihood of resource

abundance (Foreman, pers. comm. 1996). Thus, habitat loss due to oil

and gas exploration and development no longer threatens the species.

Off-highway vehicle activities, including Border Patrol OHV

activities and authorized and unauthorized recreational OHV activities,

occur in many portions of the range of the flat-tailed horned lizard.

The level of OHV activity, however, ranges from a high level in areas

within OHV open areas to a low level in areas where existing routes are

located miles apart. The zone impacted by established routes, and the

resulting impact on local lizard populations is not known. The habitat

disturbance caused by route proliferation in the desert is visually

evident, but has not been adequately quantified at this time.

Off-highway vehicle activity can crush burrows necessary to flat-

tailed horned lizards for temperature regulation (Wone 1997), can cause

direct mortality (Muth and Fisher 1992), and modifies habitat through

shrub loss, exotic plant introduction, and soil movement (Rado 1981).

The overall impact of OHV activity on habitat and individual lizards

likely depends on the frequency and intensity of use. In OHV Open Areas

and the Ocotillo Wells State Vehicular Recreation Area (SVRA), which

include an estimated 65,200 ha (161,000 ac) of potential flat-tailed

horned lizard habitat, intensity of use is often high, and vehicular

activity is not restricted to routes. However, the population trend

data are inadequate to conclude that the flat-tailed horned lizard

population in the Ocotillo Wells SVRA is declining. Flat-tailed horned

lizard mortality on established trails has not been quantified, but is

likely to occur because of the adaptations of this species for prey

avoidance. This species relies on cryptic coloration for defense, and

rarely flees when approached. Animals that do move, usually move short

distances.

[[Page 37858]]

This behavior, combined with shallow depths of hibernation during

the winter months make mortality due to vehicular activity likely. The

BLM is conducting a route designation process that administratively

closes some existing routes, and will be continuing to work with off-

highway vehicular recreationists and wildlife biologists to identify

routes unnecessary to the recreation community.

No studies to date have documented the distance from a road over

which any population declines or impacts may occur. Although some

studies have found reduced scat abundance in areas with vehicular

tracks (Olech undated), overall, studies that have attempted to assess

the impacts of OHV use on flat-tailed horned lizards have been

inconclusive. In a small number of plots (n=6) at the Imperial Sand

Dunes in southeastern California, Bury and Luckenbach (1983) found that

areas impacted by OHV use appeared to have lower abundance of rodents,

lizards, and plants than in an equal number of control plots where

there was no OHV use. However, in plots of different OHV use

classification, Wone et al. (1990) and Wright (1993) found no

difference in the abundance of flat-tailed horned lizard scat. Klinger

et al. (1990) were not able to assess the effects of varying levels of

OHV activity because the different levels of OHV activity which they

examined occurred in different habitat types. Some disturbance due to

OHV use is unauthorized, but information concerning the amount and

impact of unauthorized use is unavailable. While OHV activity poses a

potential local threat to individual flat-tailed horned lizard

populations, there is no documentation that OHV use poses a significant

threat throughout the range of the species.

Residential, recreational and industrial development on private

lands threaten some populations of flat-tailed horned lizards within

the range of the species. However, because at least 50 percent of the

habitat available to the species is located on public lands, because

conservation measures are in place on these lands, and because the

likelihood of large scale recreational and industrial development on

these lands is low, urban, recreational, and industrial development

does not significantly threaten the species.

Agricultural conversion is one of the primary causes of habitat

loss for the flat-tailed horned lizard. Conversion continues on many

private parcels throughout the range of the species, most notably in

Coachella Valley in Riverside County, and near San Luis and Yuma,

Arizona. Like urban and industrial development, this impact is

anticipated to occur largely on private lands. Agricultural conversion

on public lands managed by signatories of the CA is not anticipated,

but if it occurred, it would be subject to mitigation and compensation

measures outlined in the Management Strategy. In addition, the

signatories have committed to not authorize agricultural development in

MAs. Because of the large acreage of habitat that exists on public

lands where agricultural conversion is less likely to occur, the

mitigation and compensation measures associated with surface

disturbance on public lands managed by CA signatories, and the acreage

further protected by the surface disturbance cap placed on MAs,

agricultural conversion threatens local populations of the flat-tailed

horned lizard, but does not threaten the species as a whole at this

time.

Sand and gravel extraction, and canal, pipeline, and transmission

line construction are impacts on flat-tailed horned lizard habitat that

have occurred on private and public lands, and may continue to do so in

the future. Canals, such as the All-American and Coachella Canals,

likely constitute complete or near complete barriers to movement of

flat-tailed horned lizards, resulting in habitat fragmentation. The

current extent of sand and gravel extraction pits on public lands is

not documented, but Rado (1981) estimated 2,070 ha (5,120 ac) of active

and intermittent sand and gravel quarries. This acreage represents a

small percentage of the habitat present on public lands. Signatories to

the CA have committed to locating such projects to areas outside of MAs

to the maximum extent possible, and will apply appropriate mitigation

and compensation measures, as identified in the Management Strategy, to

all such projects. The BLM has required appropriate mitigation and

compensation measures on BLM land since 1990.

The Area Service Highway, a proposed highway that would connect

Interstate 8 at Araby Road to the United States-Mexico Border, would

fragment an area of high quality habitat. According to Hodges (1997),

it would also result in approximately 830-1,040 ha (2,040-2,560 ac) of

lost habitat and mortality of lizards. The highway is proposed for

alignment along a portion of the western boundary of the Yuma MA. The

habitat loss and potential future mortality and indirect impacts

associated with construction of this road represent a local threat to

the lizard population. This impact will be mitigated by on-site

minimization measures and compensation fees which will be used for

habitat acquisition within MAs.

Because of the large amount of flat-tailed horned lizard habitat

located on public lands within the United States and the reduction of

threats on these lands due to changing land-use patterns and

conservation efforts of public agencies, threats due to habitat

modification and loss do not warrant listing of the species at this

time.

B. Overutilization for Commercial, Recreational, Scientific, or

Educational Purposes

Although horned lizards have been popular in the pet industry,

flat-tailed horned lizards are difficult to locate due to their cryptic

coloration. No threat from overutilization of this species is known at

this time.

C. Disease or Predation

The Service is aware of parasitism by nematodes and red mites in

some flat-tailed horned lizards (Norris 1949), but this is not

considered to be a threat to the species (Bolster and Nocol 1989).

Flat-tailed horned lizards are preyed upon by loggerhead shrikes,

round-tailed ground squirrels, snakes, and canids (Muth and Fisher

1992) as well as American kestrels, common ravens, and burrowing owls

(Duncan et al. 1994). Because lizards remain on the surface and sleep

at night, they may also be subject to predation by scorpions

(Rorabaugh, pers. comm. 1997). Recent studies on telemetered animals in

Arizona have revealed a high level of predation, with 30 percent of the

marked lizards suffering mortality due to predation. Round-tailed

ground squirrels and loggerhead shrikes were the primary predators

identified. Further research is necessary on the effects of predation,

and abundance and distribution of predators before the importance of

this factor can be fully understood. There is no evidence of population

declines in extant habitat where these predator species occur. Thus,

based on the available data, disease and predation do not significantly

threaten the species.

D. The Inadequacy of Existing Regulatory Mechanisms

The conservation of this species is linked to the protection of the

desert habitat. As outlined in the proposed rule, numerous regulatory

mechanisms are currently in place to protect the flat-tailed horned

lizard. In addition to the regulatory mechanisms in existence at the

time of publication of the proposed rule, the CA and Management

Strategy outlined in the ``Background'' section of this notice have

been signed by the

[[Page 37859]]

Service, the BLM in California, the BLM in Arizona, the California

Department of Parks and Recreation, the Arizona Department of Game and

Fish, the BoR, the Commanding Officer of the Barry M. Goldwater Range,

and the Commanding Officer of Naval Air Field El Centro. This agreement

and associated strategy provide a framework for continued management of

the flat-tailed horned lizard within the MAs designated by each of the

landholding signatories.

The States of California and Arizona prohibit the collection of

flat-tailed horned lizards except by permit. The Arizona Game and Fish

Department has further included the species on the List of Wildlife of

Special Concern in Arizona. This list includes species that may be

imperilled in Arizona. No state regulations protect the habitat of this

species. Both the Arizona Game and Fish Department and the California

Department of Parks and Recreation, however, have signed the CA and

Management Strategy, which will provide for their continued

participation in conservation efforts for this species. The Arizona

Game and Fish Department does not own or manage flat-tailed horned

lizard habitat but will continue to provide input on management

decisions, as well as input regarding status and biology of the flat-

tailed horned lizard. The state of California has designated part of

the Anza Borrego Desert State Park as an MA, which will limit surface

disturbance that could be experienced in the park. Management in Anza

Borrego is compatible with lizard conservation, due to the emphasis

placed on resource protection, regulations limiting vehicles to

designated trails, and enforcement of these policies. These policies

have been in effect for a number of years. The Ocotillo Wells State

Vehicular Recreation Area (SVRA) has supported research on the flat-

tailed horned lizard for several years, and will continue to do so as a

signatory to the CA. The SVRA has been designated a ``Research Area''

in acknowledgment of continued support of research planned.

In 1990 the California Department of Fish and Game and the BLM

developed a joint Flat-tailed Horned Lizard Management Plan to address

the species' conservation on BLM lands in California. The overall

management goal of this plan is to maintain stable populations in all

crucial habitat areas and to promote species recovery on BLM lands in

California. The BLM has been in the process of implementing this plan

since 1990.

Within California, the lizard occurs in special management areas

including three BLM Areas of Critical Environmental Concern (ACECs).

These include the East Mesa, West Mesa and Yuha Desert ACECs. The ACECs

overlap, in part, with the East Mesa, West Mesa, and Yuha Desert MAs.

The East Mesa and Yuha Desert ACECs also fall within the boundaries of

wildlife habitat areas that require preparation of habitat management

plans to address the protection of special status species such as the

flat-tailed horned lizard. This species also occurs within the

boundaries of the San Sebastian Marsh ACEC and one Wilderness Study

Area, the North Algodones Dunes Wilderness.

The ACEC and wildlife habitat area designations have had limited

success in protecting flat-tailed horned lizard habitat. Management

prescriptions within ACECs include measures such as restricting OHV

activity, but ACEC management goals include a provision to ``provide

for other uses in the designated areas compatible with the protection

of significant natural and cultural resources'' (BLM 1980).

Participation of the BLM in the development of the Management Strategy,

and subsequent signing of the CA increase the protection of flat-tailed

horned lizards that will occur within ACECs where they overlap with

MAs. The increase in protection will occur as a result of the process

identified to facilitate OHV route minimization within MAs, the

prohibition of OHV competitive events within MAs, and the limitation of

surface disturbance activities to one percent of the total area of MAs

over the course of the next five years.

The North Algodones Dunes Wilderness is managed by the BLM for

wilderness values. Motorized vehicular use is prohibited and the area

shows little evidence of human intrusion. Limited habitat for the flat-

tailed horned lizard exists in the wilderness area, but these

populations are protected by this designation.

The flat-tailed horned lizard occurs in the Coachella Valley

Preserve in Riverside County. It is reportedly not abundant within the

Preserve, but these populations are not threatened.

In Arizona, the species occurs within the boundaries of the Gran

Desierto Dunes ACEC and the extreme western portion of the Tinajas

Altas Mountains ACEC. In addition, an MA on BLM, DoD, and BoR lands has

been designated. This MA occurs in the area of high relative abundance

identified by Rorabaugh et al. (1987). Protection on the MA will

include a cap on future surface disturbance of no more than one percent

over the course of the next five years, as well as other conservation

measures identified as part of the Management Strategy. The U.S. Marine

Corps has agreed to comply with the terms and conditions of a

conference opinion issued by the Service whether or not the species is

listed. Terms and conditions, which are currently being implemented,

include among others, limitations on surface disturbance, establishment

of a speed limit, and enforcement of ``no trespass'' requirements. In

addition, the Marine Corps is acquiring State of Arizona inholdings

within the MA on the Barry M. Goldwater Range.

E. Other Natural or Manmade Factors Affecting Its Continued Existence

Natural and manmade factors identified in the proposed rule as

threats to the species included insecticide spraying associated with

the Curlytop Virus Control Program and drought. Since publication of

the proposed rule, the BLM has issued a Record of Decision prohibiting

insecticide spraying in MAs. This spraying program was thought to have

contributed to population declines in East Mesa (Bolster and Nicol

1989). Since impacts due to pesticide application have been reduced,

this activity no longer threatens flat-tailed horned lizard populations

within MAs.

Precipitation has been correlated with insect abundance and lizard

densities (Turner et al. 1982). Within the range of the flat-tailed

horned lizard, rainfall is highly unpredictable, both temporally and

spatially (Turner and Brown 1982). Localized areas may experience long-

term drought, which may result in local decreases in lizard

populations. Because of the fragmented distribution of the flat-tailed

horned lizard, this unpredictability in precipitation increases the

chance of localized extirpations. Data are inadequate to properly

assess the degree to which drought or other naturally occurring events

may increase the probability of extirpation.

Finding and Withdrawal

The Service has carefully assessed the best scientific and

commercial information available regarding the past, present, and

future threats to this species. Flat-tailed horned lizard population

trend data are inadequate to conclude that significant population

declines have occurred in extant flat-tailed horned lizard habitat

since publication of the proposed rule. Population trend information

remains ambiguous due to uncertainties raised since publication of the

proposed rule regarding survey methodology and analysis. Past and

projected flat-tailed

[[Page 37860]]

horned lizard habitat loss due to agricultural, urban, industrial, and

recreational development has and continues to occur on private lands.

Large blocks of habitat with few anticipated impacts exist on public

lands throughout the range of this species in East Mesa, West Mesa,

Yuha Desert, Yuma, and Anza Borrego Desert. Since the publication of

the proposed rule to list the flat-tailed horned lizard as threatened,

several of the threats identified on public lands have been reduced or

eliminated. Threats that have been reduced include those due to

geothermal development, oil and gas development, and pesticide

spraying. In addition, the conservation commitment of the agencies has

increased with the signing of a CA and Management Strategy designed to

protect the flat-tailed horned lizard on public lands. MAs have been

designated in the Yuha Desert, West Mesa, East Mesa, Yuma Desert, and

Anza Borrego State Park. Development of the CA has further reduced

threats, as agencies begin to implement actions identified in the

Management Strategy.

Because of re-evaluation of information presented in the proposed

rule, significant reduction of threats on public land, and

uncertainties regarding population trend data, the Service determines

that the flat-tailed horned lizard does not meet the required criteria

to afford this species threatened status under the Act.

The Service will work actively to gather additional information on

its status as part of the Flat-tailed Horned Lizard Interagency

Coordinating Committee. Further, the Service will continue to

participate with parties of the CA to conserve this species as part of

the Flat-tailed Horned Lizard Management Oversight Group.

References Cited

A complete list of all references cited is available at the

Carlsbad Field Office (see ADDRESSES above).

Author

The primary author of this document is Sandy Vissman, Carlsbad

Ecological Services Field Office (see ADDRESSES section).

Authority

The authority for this action is section 4(b)(6)(B)(ii) of the

Endangered Species Act of 1973, as amended (16 U.S.C. 1531 et seq.).

Dated: July 10, 1997.

John G. Rogers,

Acting Director, Fish and Wildlife Service.

[FR Doc. 97-18688 Filed 7-14-97; 8:45 am]

BILLING CODE 4310-55-P