boundary of the El Mirage Open Area, along the Mojave-Randsburg Road, and on many cattle
allotments are examples. This memo concerns tortoise-proof fences, which have a hardware
cloth component and are intended to preclude tortoises from a given area (i.e., usually an impact
area at a construction or mine site).
In general, there are at least three types of tortoise-proof fences: (1) temporary fences to
preclude tortoises from a given area (i.e., usually active construction sites) for a short amount of
time (i.e., usually weeks or months, in some cases, days); (2) permanent fences to preclude
tortoises from a given area and minimize human impacts to tortoises in perpetuity; and (3)
special-condition fences, which are usually permanent, and tailored to meet specific needs.
Guidelines for using each fence type are described below. The Implementation Team may
modify these guidelines as new information becomes available or where the particular project
type calls for modification of these guidelines.
1. Temporary Tortoise-Proof Fences.
1.a. Intended Function.
This fence type is intended to preclude tortoises from an active
construction site, where said activities (a) are likely to adversely affect tortoises; (b) are of short
duration, usually a matter of weeks or months; and (c) fencing is less expensive and equally
effective compared to having an environmental monitor remain on-site for a prolonged period of
time. In this case, tortoises are known to occur in or adjacent to the impact area, which would be
determined at the time of the clearance survey. This type of fence is best used on a fixed
construction site [i.e., new or expanding mine area, residential development on a relatively small
parcel (i.e., less than about 100 acres), etc.]. Pipelines and other long, linear projects are not well
suited for temporary tortoise-proof fences, although fences have been effectively used during
construction of pump houses, booster stations, stationary excavations, etc. along the right-of-
way. In general, installing the temporary tortoise-proof fence is less expensive than employing
an environmental monitor for the duration of the ground-disturbing activity.
The West Mojave Plan requires that all areas within Tortoise DWMAs and
additional areas within a Tortoise Survey Area are to be surveyed for tortoises prior to ground
disturbance. If during this clearance survey, the Authorized Biologist or Environmental Monitor
(accompanied by the biologist) finds tortoise(s) on the site or in adjacent areas, a set of Best
Management Practices, which may include fence installation, would be implemented to avoid
take of tortoises. If a temporary tortoise-proof fence is to be erected, it should be placed around
the perimeter of the area to be impacted, allowing sufficient room for construction activities to
occur inside the fence without harm to construction personnel. The Authorized Biologist or
Environmental Monitor would remain on-site and assist construction personnel or the fencing
contractor in the placement of the fence to keep as many tortoise burrows as possible outside the
fence. Once the fence is erected, the fenced area would be surveyed for tortoises and burrows, as
described in the BMPs. All burrows would be excavated, and all tortoises and tortoise eggs
would be moved out of harm’s way, outside the fenced area, as described in Attachment I-1
(Guidelines for Relocating Tortoises During Authorized Construction Projects in All Occupied
Tortoise Habitats). Once the site is cleared of tortoises, the biologist or monitor need not remain
on-site, so long as all construction activities are restricted to and contained within the temporary
1.c. Materials and Installation.
In general, the temporary tortoise-proof fence would
consist of 24-inch wide, 2-inch mesh, galvanized hardware cloth attached to 36-inch tall rebar or
other post material. It may be advisable to clear a narrow (3- to 4-foot wide) path in which the
fence would be installed, although the fence may be installed without removing any vegetation.
The mesh is then folded in half, creating a 12-inch vertical portion and a 12-inch horizontal
portion, at more-or-less right angles to each other. When installing the fence, it is important that
the horizontal portion of the fence lie evenly on the ground surface and face outward from
the fenced area. In so doing, when a tortoise excluded from the fenced area encounters the
vertical portion of the fence, it would be standing on the horizontal portion of the fence, which
will restrict its ability to burrow beneath the fence and enter the impact area. Rebar or other post
material should be spaced at about 10-foot intervals, although the specific situation may require
closer intervals (i.e., as in extremely rocky areas) or allow for wider intervals. In any case, post
placement should ensure that no gaps exist in the fencing material between the posts. The
fencing material is then attached to the rebar with hog rings, fence clamps, or other fasteners.
Once attached, the horizontal portion of the fence (which is effectively outside the fenced area)
should be covered with soil or rocks, or otherwise secured to the ground surface, so that no gaps
allow for tortoise immigration into the impact area. Finally, it may be appropriate to tie
surveyor’s flagging or other highly visible material to the tops of the posts to increase the
visibility of the fence, so that construction personnel avoid tripping on the fence and vehicles
avoid damaging it.
There is no evidence that hurricane fencing, plastic mesh, or similar materials will
preclude tortoises from an area; tortoises, and lizards in particular, often get their heads or
appendages stuck in chicken wire and fencing materials with a mesh size larger than 2 inch; until
new information shows otherwise, these materials should not be used as alternate fencing
One or more gates will be necessary to allow entry and exit of construction
vehicles onto the site. There are no specific gate designs associated with the temporary fence,
although it must function to preclude tortoises from the area. The gate may be an extension of
the fence line, and opened inwards or outwards to allow for vehicle passage. As with the fence,
the horizontal portion of the gate should face out from the fenced area. Keeping the gate closed
when vehicles are not actively entering or leaving the site has been a major problem in the past,
and undermines the effectiveness of the fence. As a guideline, if construction is occurring
during the tortoise inactivity period, generally from November 15 to February 15, there is
probably no need to close the gate. However, it should be closed at all times when not in use
between February 15 and November 15, or if tortoises are known to be active in the area.
1.e. Monitoring and Maintenance.
It is essential that someone be assigned the
responsibility of periodically walking (or driving, if conditions warrant) the fence line to ensure
its integrity and effectiveness in precluding tortoises from the impact area. Whereas this may be
accomplished with weekly or monthly inspections, it is important to check the fence after each
rain storm to ensure no gaps in the material. Most breaches are remedied by replacing soil or
rocks on the horizontal portion of the fence to close the gap.
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2. Permanent Tortoise-Proof Fences.
2.a. Intended Function.
This fence type is intended to exclude tortoises, including
hatchlings, from a given area in perpetuity. It may also function to minimize human impacts on
tortoises occurring in adjacent areas. A permanent tortoise-proof fence is generally
recommended for facilities in tortoise habitat where there are regular visits to the facility (e.g.,
pump stations, tank sites, vehicle storage yards, etc.) for the foreseeable future. The need for
such a fence should be determined on a case-by-case basis by the Implementation Team, and be
based as much as possible on the known occurrence of tortoises in the area. A permanent
tortoise-proof fence in downtown Victorville is a waste of money, as no tortoises occur in the
interior, urban portions of this and many other desert communities.
As with the temporary tortoise-proof fence, the permanent fence should be
installed as early as possible, preferably before ground-disturbing activities. If that is not
feasible and a temporary fence is used, the permanent fence should be installed inside the
temporary fence as part of the contained construction activities. As its name implies, the
permanent fence would remain in place in perpetuity, or for as long as the facility is in operation.
2.c. Materials and Installation.
The description given above for the temporary fence is
also applicable to the permanent fence, with two important exceptions: the hardware cloth is
attached to a more substantial fence (i.e., usually chain-link or range fencing) and it is buried.
The same 24-inch wide, 2-inch mesh, galvanized hardware cloth should be buried to a depth of
about 6 to 8 inches, with the remaining portion securely attached to the more substantial fence.
If a temporary fence is installed first, followed later by the permanent fence, the same hardware
cloth may be used for both. Ditch witches, backhoes, and other heavy equipment are often used
to excavate a trench in which the bottom portion of the hardware cloth is buried. If the ground is
too rocky and precludes burying the fence, the contractor must still ensure that the fence
excludes tortoises from the area. Three-to-four-inch galvanized posts are often used with chain-
link, and t-posts are often used with range fencing, but in any case, the permanent fence should
be sturdy enough to remain in place in perpetuity. Installation of these fences should be
monitored, unless the fence can be installed alongside existing roads, and even then, the biologist
still needs to survey the fenced area to excavate all tortoise burrows and move all tortoises/eggs
out of harm’s way, to outside the fenced area.
Whereas the temporary gate may be as rudimentary as a fold in the extended
fence line, the gate on a permanent tortoise-proof fence must be more substantial and sufficiently
sturdy to withstand years of use and still function to preclude tortoises. Cement foundations and
permanent footings have been used effectively in blocking the gap at the bottom of gates that are
frequently used. In cases where there are infrequent visits, hardware cloth may be attached to
the bottom of the gate, and closely fit the ground surface to preclude tortoises from entering the
site. Often, this type of tortoise-proof gate material drags across the ground as the gate is opened
and closed. Keeping the gates closed to frequently used facilities is a persisting problem.
Maintaining a closed-gate policy from February 15 to November 15 is advisable.
2.e. Monitoring and Maintenance.
Monitoring and maintaining permanent tortoise-proof
fences is important. Given that the bottom of the fence is buried, it may not be necessary to
check the fence as often as the temporary fence. However, maintaining the integrity of a
permanent fence is equally or more important than the temporary fence, and will require an
extended monitoring program for as long as the fence remains in place. Curing breaches in a
permanent fence may require heavy equipment and is likely to be more time consuming than
fixing a gap in a temporary fence. A single storm event may erode away soil from the buried
fence, and should be considered in the monitoring and maintenance procedures for the
3. Special Condition Fences.
Finally, in about 1996 (revised 29 January 2002), Dr. Bill Boarman assisted Caltrans in
designing a tortoise-proof fence and culverts for the Highway 58 widening project. The
following narrative and diagram were provided by Dr. Boarman as one example of how such a
fence would be installed and function:
Specifications for Culverts and Tortoise-proof Fence along Highway 58, San
Bernardino County, California.
These comments are not to be considered a recommendation; they only serve to
explain the current design of the culverts and tortoise-proof fence in place along a fifteen-
mile stretch of State Highway 58 between Barstow and Kramer Junction, San Bernardino
County, California. The fence consists of 6-strand highway right-of-way fencing with 1/2-
inch mesh galvanized hardware cloth sunk part-way into the ground (Figure 1). The fence is
connected to several storm-drain culverts that span the entire width of the highway, thus
permitting access by tortoises to the culverts.
The basic fence right-of-way consists of 7-foot long metal posts (t-bars) sunk 2 feet
6 inches into the ground and spaced approximately ten feet apart. There are six strands of
wire placed about 10 inches apart. The top three strands are barbed, the bottom three are
unbarbed strands of 10-gage galvanized wire; this allows medium-sized mammals to climb
over without injury. The tortoise-proof feature is made of 24-inch wide, 1/2-inch mesh, clear
galvanized steel hardware cloth that is attached to each metal post with steel rings. The cloth
is sunk 6 inches into the ground, leaving 18 inches of exposed cloth.
An additional feature of the fence is a specially designed tortoise-proof gate placed
at varied intervals along the fence. The gate is a standard 12-foot wide gate with a central
vertical stay and attached to a 7-foot metal gate post which is sunk 3 feet into the ground.
The 24-inch wide, 1/2-inch mesh, clear galvanized steel hardware cloth is attached to the
lower 2 feet of the gate, flush with the bottom of the gate. Beneath the gate, parallel to the
gate in a closed position, is an 8 inch by 8 inch by 12 foot Douglas Fir beam sunk completely
into the ground with its top edge flush with the ground surface. The gate is hung with a 1/2-
inch clearance above the Douglas Fir post.
The culverts are located in washes since they were placed to facilitate water runoff,
not tortoise movements. The 156 to 206 foot-long culverts are made of 36 to 60 inch,
corrugated steel pipe, 54 inch, reinforced concrete pipe, and 10 ft to 12 ft by 6 ft to 10 ft,
reinforced concrete boxes. The culverts cross beneath the entire width of the highway and
connect directly to the fence, thus providing an unobstructed pathway between both sides of
the fenced highway. The entrance to each culvert is to be maintained to prevent erosion
exposing the edge of the culvert or creating gullies, both of which may prohibit tortoise use
of the culverts.
I.2 BEST MANAGEMENT PRACTICES FOR DESERT
TORTOISE SURVEY AREAS (OUTSIDE DWMAs)
The measures given below comprise a subset of the BMPs developed for construction
projects in Tortoise DWMAs, and are modified as necessary for applicability to Incidental Take
Areas outside DWMAs where focused desert tortoise surveys would be required (i.e.,
specifically within Tortoise Survey Areas).
Although DWMAs represent essential habitats required for the conservation and recovery
of the desert tortoise, the California Department of Fish and Game (Department) and U.S. Fish
and Wildlife Service (Service) require that the take of tortoises be minimized insofar as possible
in all areas supporting tortoises, not just in DWMAs. The West Mojave Plan (Plan) has used
the best available data to delineate areas where clearance surveys would (Tortoise Survey Area)
and would not (Tortoise Non-Survey Areas) be required for projects covered by the Plan.
In the Tortoise Non-Survey Areas, a clearance survey would not be required, rather, at
the time of discretionary permit issuance, the pertinent lead agency (i.e., mostly counties and
cities) would distribute a brochure that, among other things, includes a hotline number to be
called in the unlikely event a wild tortoise would be encountered.
The following BMPs are recommended for Tortoise Survey Areas:
1. The Implementation Team would maintain a list of Authorized Biologists who are qualified
to perform desert tortoise clearance surveys. Environmental Monitors, who also must be
approved by the Implementation Team, may assist the Authorized Biologist but are not
authorized to perform clearance surveys by themselves.
2. The following guidelines are given to direct the timing of clearance surveys prior to ground-
disturbing activities based on the assumption that most tortoises (with the exception of juveniles)
are in hibernation from November 15 through February 15:
(a) Between February 15 and November 15, the clearance survey shall occur
within 48 hours prior to ground disturbance.
(b) Between November 16 and February 14, the survey may be performed several
days or several weeks prior to ground disturbance.
3. In general, the clearance survey shall include 100% of the area to be developed (Impact Area)
and be conducted along transects spaced at 30-foot intervals on flat, open terrain or at shorter
intervals (e.g., 15-20 feet apart) in dense vegetation, rocky hillsides, or in other situations where
substrates are not easily observed.
4. If no tortoise sign is found on the site, the Authorized Biologist shall judge the likelihood of
tortoise occurrence in the adjacent area.
5. If the Authorized Biologist judges that tortoises are absent from the area AND would not be
directly affected by construction activities (i.e., are not likely to immigrate onto the site), the
Authorized Biologist shall convey that information to personnel directly responsible for ground-
disturbing activities, and leave an educational brochure outlining measures to be taken if a
tortoise is encountered.
6. If tortoises or intact (i.e., active) tortoise burrows are found in the Impact Area OR if the
Authorized Biologist is reasonably sure that a tortoise may enter into the construction site, take
avoidance measures shall be implemented. Any tortoises within the Impact Area shall be
removed and relocated as per guidelines given in Attachment I-1. Tortoises outside the Impact
Area shall not be handled or otherwise disturbed.
7. All burrows in the Impact Area, including those not recently used, shall be excavated at the
time of the survey. Eggs shall be relocated as they are found (see Desert Tortoise Council,
8. Once the initial tortoises are removed and burrows excavated, the site shall then be surveyed
an additional time to located any tortoises or burrows missed by the first survey. The site would
then be considered clear, and ground-disturbing activities may proceed.
9. The Authorized Biologist shall remain on-site until it is completely brushed.
10. Upon locating a recently dead or injured desert tortoise, the Authorized Biologist shall
immediately notify the Lead Federal Agency (for federal projects) or Implementation Team (for
non-federal projects). Where appropriate, it is recommended that tortoise remains be collected
and stored as given in Dr. Kristin Berry’s protocol for salvaging dead and sick tortoises. Written
notification shall be made within five days of the finding to the Implementation Team and the
Service’s Division of Law Enforcement in Torrance. The information provided shall include the
date of the finding or incident (if known), location of the carcass or injured animal, a
photograph, cause of death (if known), and other pertinent information. Injured animals shall be
transported to a qualified veterinarian for treatment at the expense of the project proponent. If
injured animals recover, the project proponent shall contact the Implementation Team for final
disposition of the animals.
11. Authorized Biologists and Environmental Monitors are advised to follow the appropriate
guidelines outlined in Guidelines for Handling Desert Tortoises during Construction Projects,
Appendix 2 (Desert Tortoise Council 1994, revised 1999).
I.2.2 Educational Brochure
12. The Implementation Team will develop and make available a standard education brochure,
and maintain a list of Authorized Biologists and Environmental Monitors who are authorized to
distribute the brochure. Among other things, this brochure shall outline steps to be taken if a
enters into the construction site once the Biologist/Monitor has left the site.
I.2.3 Preconstruction Planning
13. Whenever possible, the project proponent shall work with the Implementation Team to plan
for and conduct construction activities (particularly linear projects through Tortoise Survey
Areas) when tortoises are least likely to be active, which generally occurs between November 15
and February 15.
14. Where more than one site or alignment could satisfy the project proponent’s needs, it is
suggested that a presence-absence survey be conducted on the alternative sites to determine
which site or alignment will result in the fewest impacts to tortoises and occupied habitat during
15. Authorized Biologists and Environmental Monitors shall maintain records of all desert
tortoises and other covered species encountered during project activities, including the following
information: (a) the locations (narrative and maps) and dates of observations; (b) general
condition and health, including injuries and state of healing and whether animals voided their
bladders; (c) locations from which and to which any animals are moved (UTM coordinates
derived from a global positioning system - GPS - are preferable); (d) diagnostic markings (i.e.,
identification numbers or marked lateral scutes); and (e) the amount of habitat lost (i.e., cleared
of vegetation) to the activity. This report shall be submitted to the Implementation Team within
30 days of the Authorized Biologist leaving the site.
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