DEPARTMENT OF THE INTERIOR

Fish and Wildlife Service

50 CFR Part 17

\[FWS-R8-ES-2008-0086; 92210-5008-3922-10-B2\]

Endangered and Threatened Wildlife and Plants; 90-Day Finding on a
Petition To List the Dusky Tree Vole (*Arborimus longicaudus silvicola*)
as Threatened or Endangered

AGENCY: Fish and Wildlife Service, Interior.

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

SUMMARY: We, the U.S. Fish and Wildlife Service (Service), announce a
90-day finding on a petition to list the dusky tree vole (*Arborimus
longicaudus silvicola*) in all of its range as threatened or endangered
under the Endangered Species Act of 1973, as amended (Act). The
petitioners also requested the Service to list either the north Oregon
coast population of the red tree vole (*A. longicaudus*) as a Distinct
Population Segment (DPS) or the red tree vole throughout all of its
range because it is threatened or endangered in a significant portion of
its range, if we determined that the subspecies, *A. l. silvicola*, was
not a valid taxon.

We find that the petition presents substantial scientific or commercial
information indicating that listing the dusky tree vole as a subspecies
may be warranted. Therefore, with the publication of this notice we are
initiating a status review of the species, including the evaluation of
the north Oregon coast population of red tree vole and the red tree vole
throughout its range, and we will issue a 12-month finding on our
determination as to whether the petitioned action is warranted. To
ensure that the status review is comprehensive, we are soliciting
scientific and commercial data and other information regarding this
species. We will make a determination on critical habitat for this
species if, and when, we initiate a listing action.

DATES: To allow us adequate time to conduct this review, we request that
information you submit be received by us on or before **\[**\[INSERT
DATE 60 DAYS AFTER DATE OF PUBLICATION IN THE FEDERAL REGISTER\]**\]**.

ADDRESSES**:** You may submit information by one of the following
methods:

• Federal eRulemaking Portal: *http://www.regulations.gov*. Follow the
instructions for submitting comments.

• U.S. mail or hand-delivery: Public Comments Processing, Attn: FWS-
R8-ES-2008-0086; Division of Policy and Directives Management; U.S. Fish
and Wildlife Service; 4401 N. Fairfax Drive, Suite 222; Arlington, VA
22203.

We will not accept e-mail or faxes. We will post all information
received on [*http://www.regulations.gov*](http://www.regulations.gov/).
This generally means that we will post any personal information you
provide us (see the Information Solicited section below for more
details).

FOR FURTHER INFORMATION CONTACT: Paul Henson, Project Leader, Oregon
Fish and Wildlife Office, 2600 SE 98^th^ Avenue, Portland, OR 97266; by
telephone (503-231-6179); or by facsimile (503-231-6195). Persons who
use a telecommunications device for the deaf (TTD) may call the Federal
Information Relay Service (FIRS) at 800-877-8339.

SUPPLEMENTARY INFORMATION:

Information Solicited

When we make a finding that a petition presents substantial information
indicating 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 concerning the
status of the red tree vole (*Arborimus longicaudus*), a species that
includes the dusky tree vole (*A. l. silvicola*). We request information
from the public, other concerned governmental agencies, Native American
Tribes, the scientific community, industry, or any other interested
parties concerning the status of the red tree vole, inclusive of the
dusky tree vole**.** We are seeking information regarding (1) the
taxonomic validity of *A*. *l*. *silvicola*; (2) the discreteness and
the significance of the red tree vole population on the north Coast of
Oregon; and (3) that area constituting a significant portion of the
species' range; including: (a) information on the historical and current
distribution of the red tree vole, inclusive of the dusky tree vole,
throughout its range and the effects of past habitat management on that
distribution; (b) information related to red tree vole population
abundance, dynamics, and trends in this area; (c) genetic,
morphological, behavioral, and other information relating to the
taxonomy of the red tree vole, inclusive of the dusky tree vole; and (d)
information relevant to whether any population of the red tree vole in
western Oregon may qualify as a DPS in accordance with the "Policy
Regarding the Recognition of Distinct Vertebrate Population Segments
under the Act" (Service 1996) (the policy is available at
*http://www.fws.gov/endangered/policy/pol005.html* or at the Oregon Fish
and Wildlife Office (see FOR FURTHER INFORMATION CONTACT)).

We seek additional information on the distribution of the red tree vole
to clarify the range of the three potential listable entities described
by the petitioner: (1) the dusky tree vole subspecies; (2) the north
Oregon coast population of the red tree vole, which occupies the same
range as the dusky tree vole; and (3) the red tree vole throughout all
of its range.

We are also seeking information pertaining to the following five threat
factors used to determine if a species, as defined under the Act, is
threatened or endangered pursuant to Section 4(a)(1) of the Act:

\(a\) the present or threatened destruction, modification, or
curtailment of the species' habitat or range;

\(b\) overutilization for commercial, recreational, scientific, or
educational purposes;

\(c\) disease or predation;

\(d\) the inadequacy of existing regulatory mechanisms; or

\(e\) other natural or manmade factors affecting its continued existence
and threats to the species or its habitat.

If we determine that listing the dusky tree vole, listing the north
Oregon coast DPS of the red tree vole, or listing the red tree vole
throughout all of its range because it is threatened or endangered in a
significant portion of its range, is warranted, it is our intent to
propose critical habitat to the maximum extent prudent and determinable
at the time we propose to list the species. Therefore, with regard to
areas within the geographical range currently occupied by the species,
we also request data and information on what may constitute physical or
biological features essential to the conservation of the species, where
these features are currently found, and whether any of these features
may require special management considerations or protection. In
addition, we request data and information regarding whether there are
areas outside the geographical area occupied by the species that are
essential to the conservation of the species. Please provide specific
comments and information as to what, if any, critical habitat you think
we should propose for designation if the species is proposed for
listing, and why such habitat meets the requirements of the Act.

[]{.mark}

Please note that submissions merely stating support for or opposition to
the action under consideration without providing supporting information,
although noted, will not be considered in making a determination, as
section 4(b)(1)(A) of the Act (16 U.S.C. 1531 et seq.) directs that
determinations as to whether any species is a threatened or endangered
species must be made "solely on the basis of the best scientific and
commercial data available." Based on the status review, we will issue a
12-month finding on the petition, as provided in section 4(b)(3)(B) of
the Act.

You may submit your information concerning this status review by one of
the methods listed in the ADDRESSES section. We will not consider
submissions sent by e-mail or fax or to an address not listed in the
ADDRESSES section.

If you submit information via *http://www.regulations.gov*, your entire
submission---including any personal identifying information---will be
posted on the website. If your submission is made via a hardcopy that
includes personal identifying information, you may request at the top of
your document that we withhold this personal identifying information
from public review. However, we cannot guarantee that we will be able to
do so. We will post all hardcopy submissions on
[*http://www.regulations.gov*](http://www.regulations.gov/).

Information and materials we receive, as well as supporting
documentation we used in preparing this finding, will be available for
public inspection on *http://www.regulations.gov*, or by appointment
during normal business hours at the Oregon Fish and Wildlife Office (see
FOR FURTHER INFORMATION CONTACT).

Background

Section 4(b)(3)(A) of the Act requires that we make a finding on whether
a petition to list, delist, or reclassify a species presents substantial
scientific or commercial information to indicate that the petitioned
action may be warranted. Such findings are based on information
contained in the petition, supporting information submitted with the
petition, and information otherwise readily available in our files at
the time we make the determination. 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 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.
We base this finding on information provided by the petitioner that we
determined to be reliable after reviewing sources referenced in the
petition and available in our files. We evaluated that information in
accordance with 50 CFR 424.14(b). Our process in making this 90-day
finding under section 4(b)(3)(A) of the Act and § 424.14(b) of our
regulations is limited to a determination of whether the information in
the petition meets the "substantial information" threshold.

On June 22, 2007, we received a petition dated June 18, 2007, from the
Center for Biological Diversity, Oregon Chapter of the Sierra Club,
Cascadia Wildlands Project, Oregon Wild, Audubon Society of Portland,
Noah Greenwald, and Amanda Garty (hereafter, "the petitioners"). The
petitioners requested that we list the dusky tree vole as a threatened
or endangered species and to designate critical habitat for it. The
petition clearly identifies itself as such, but it does not include the
requisite identification information of addresses, telephone numbers,
and signatures of petitioners, as stipulated in 50 CFR 424.14(a).
Nevertheless, we recognize the document as a petition. The petitioners
assert that the dusky tree vole is a valid subspecies of the red tree
vole, but they also note that recent scientific studies question the
validity of this subspecies. The petitioners request if we find that the
dusky tree vole is not a listable entity as a subspecies, that we either
list the north Oregon coast population of the red tree vole as a DPS, or
list the red tree vole because it is threatened or endangered in a
significant portion of its range, including the north Oregon coast
population.

On September 26, 2007, we sent a letter to Noah Greenwald, Center for
Biological Diversity, acknowledging our receipt of the petition and
providing our determination that emergency listing was not warranted for
the species at that time. We also stated our intention to make an
initial 90-day finding within 90 days of the date of our response
letter. This notice constitutes our 90-day finding for the petition to
list the dusky tree vole as a subspecies in all of its range, or, if the
subspecies is not considered valid, to list the north Oregon coast
population of the red tree vole as a DPS, or the red tree vole
throughout all of its range because it is threatened or endangered in a
significant portion of its range (inclusive of the range of the dusky
tree vole).

Listable Entity Evaluation

Under Section 3(16) of the Act, we may consider for listing any species
or subspecies of fish, wildlife, or plants, or any distinct population
segment of vertebrate fish or wildlife which interbreeds when mature.
Such entities are considered eligible for listing under the Act (and
are, therefore, referred to as "listable entities"), should they be
determined to meet the definition of a threatened or endangered species.
In this case, the petitioner has requested that we consider the
following entities for listing, presented in priority order: (1) the
dusky tree vole if it can be considered a valid subspecies of the red
tree vole; (2) the north coast population of the red tree vole, which
occupies the same range as the dusky tree vole as a DPS; or (3) the
entire range of the red tree vole because it is threatened or endangered
in a significant portion of its range. Each of these entities may be
considered for listing under the Act (16 U.S.C. 1532(16)).

The petitioners describe the range of the dusky tree vole as extending
"throughout north coastal Oregon, in Clatsop, Tillamook and Lincoln
Counties \[citations omitted\]." In the absence of information to the
contrary in the petition, we have assumed that this range description
also applies to the presumed north Oregon coast DPS of the red tree
vole, and includes all or part of the significant portion of the range
of the red tree vole in which the petitioners believe threats exist such
that listing may be appropriate.

The petitioners assert that the dusky tree vole is a subspecies of the
red tree vole based on pelage color (Hall 1981, p. 788), and believe
genetic work by Miller et al. (2006) may provide support for
distinguishing genetic differences between the dusky tree vole and the
red tree vole. The petitioners also note that Howell (1926, p. 35)
described several physical differences between the dusky and red tree
voles. The petitioners, however, acknowledge other work noting no
differences between the taxa based on physical measurements, chromosomal
analysis, and mitochondrial DNA (Johnson and George 1991, p. 12;
Bellinger et al. 2005, p. 207). We note, as do the petitioners, that the
taxonomic validity of the dusky tree vole as a subspecies is in
question. Furthermore, we note that information readily available in our
files does not support the petitioners' contention that the dusky tree
vole is a recognized subspecies of the red tree vole (Integrated
Taxonomic Information System 2007 (ITIS; *http://www.itis.gov*)).

The standard of review for a 90-day petition finding is "that amount of
information that would lead a reasonable person to believe that the
measure proposed in the petition may be warranted." We determine that
the petitioners have met the threshold for review in their
characterization of the debate over the taxonomy of the dusky tree vole,
and presented substantial information indicating that recognition of the
dusky tree vole as a subspecies may be valid, although this does not
constitute a final determination on the taxonomic validity of the dusky
tree vole as a subspecies.

If we determine that the dusky tree vole does not warrant listing as a
subspecies, the petitioner requested that we assess either whether the
north coast population of the red tree vole, which occupies the same
range as the dusky tree vole, warrants listing as a DPS, or whether the
red tree vole warrants listing because it is threatened or endangered in
a significant portion of its range. As appropriate, we will further
evaluate these other entities in the status review.

Species Information

As a putative subspecies, the dusky tree vole is a member of the red
tree vole taxon. Some of the scientific literature is specific to the
dusky tree vole, but much of it describes the red tree vole and does not
distinguish among subspecies. For that reason, available information on
the red tree vole is presented below with the assumption that it may
also apply to the dusky tree vole. If the information source makes
distinctions between the two, they are noted, as appropriate. Published
literature on the red tree vole also includes work conducted on the
closely related Sonoma tree vole (*Arborimus pomo*). Prior to 1991,
these two taxa were considered to be the red tree vole (Johnson and
George 1991, entire). Where pertinent information is lacking or limited
for the red tree vole, information on the Sonoma tree vole (*A. pomo*)
is presented.

Information presented in this section is preliminary. We have reviewed
the references cited by the petitioners, summarized that information,
and have provided additional information from references cited within
documents referenced by the petitioners. We have also included
information obtained from our ITIS database.

*Taxonomy and Description*

Tree voles are small rodents, less than 8 inches (206 millimeters) long
and weighing up to 2 ounces (50 grams) (Hayes 1996, p. 1; Verts and
Carraway 1998, p. 301). Their coat color ranges from brownish red to
bright brownish-red or orange-red (Maser et al. 1981, p. 201). The
darker coat color is characteristic of the dusky tree vole (Bailey 1936,
p. 198; Maser et al. 1981, p. 201). Melanistic (all black) forms of the
dusky (Hayes 1996, p. 1) and red tree vole (Swingle 2005, p. 46) also
occur, as do cream-colored red tree voles (Swingle 2005, p. 82).

Howell (1926, p. 35) described several physical differences between the
dusky and red tree voles. These differences include coat color, as well
as skull and dental characteristics. However, Howell (1926, p. 34) based
his description of the red tree vole on the observations of 40 voles, 32
of which were from California. At least 28 of the California voles were
collected from locales within the range of what is now considered the
Sonoma tree vole (e.g., specimens from Carlotta, located in Humboldt
County (Howell 1926, p. 41). Hence, his description of the red tree vole
and comparison to the dusky tree vole was from a collection that was
comprised primarily of Sonoma tree voles.

The red tree vole was first described from a specimen collected in Coos
County, Oregon (True 1890, p. 303-304), and originally placed in the
genus *Phenacomys*. The dusky tree vole was first described from a dead
specimen found in Tillamook County (Howell 1921, entire). The dusky tree
vole was originally classified as a distinct species, *Phenacomys
silvicolus*; Miller (1923, p. 400, as cited in Hayes 1996, p. 1) later
renamed it *P. silvicola*. Johnson (1968, p. 27; 1973, p. 243) suggested
separating the tree voles from the genus *Phenacomys*, and putting them
into their own genus, *Arborimus*. There is no agreement on the generic
classification of tree voles, with some authors continuing to use
*Phenacomys* (e.g., Verts and Carraway 1998, pp. 309-311), while others
refer to *Arborimus* (e.g., Hayes 1996, entire). The specific name,
*longicaudus*, however, is not in dispute. For the purposes of this
finding, we use the generic classification, *Arborimus*, adopted by the
petitioners.

Johnson (1968, p. 27) concluded from his analysis of blood proteins and
hemoglobin of the dusky and red tree voles that the named forms of
*Arborimus* should be combined into a single species. Hall (1981, p.
788) cited Johnson (1968, p. 27) as suggesting a "subspecific
relationship of the two taxa," and others have cited Johnson as well in
supporting the classification of the dusky tree vole as a subspecies
(e.g., Maser and Storm 1970, p. 64; Johnson and George 1991, p. 1).
However, Bellinger et al. (2005, p. 207) suggested that subspecific
status may not be warranted based on a lack of detectable genetic
differences and a lack of consistently verifiable morphological
differences between the dusky and red tree voles. Miller et al. (2006,
entire) found genetic discontinuities in the red tree vole along
north-south and east-west gradients within its range, but remained
silent on its taxonomic status. Information in our files does not refer
to the dusky tree vole as a subspecies of the red tree vole (information
retrieved 19 December 2007, from the ITIS database).

*Range and Distribution*

The *Arborimus* genus is endemic to the humid coniferous forests west of
the crest of the Cascade Mountains in Oregon and northwestern California
(Maser 1966, p. 7). The red tree vole occurs in western Oregon from the
Cascade crest to the Pacific coast (Hayes 1996, p. 2; Verts and Carraway
1998, pp. 309-310), with a geographic range covering approximately 16.3
million acres across multiple ownerships (USDA and USDI 2007, p. 287).

The southern boundary of the red tree vole's range grades into the range
of the Sonoma tree vole, which has only recently been classified as a
separate species from the red tree vole (Johnson and George 1991, p.
12). Johnson and George (1991, pp. 11-12) concluded that the range break
between these two species is the Klamath Mountains along the
Oregon-California border. Murray (1995, p. 26), however, considers the
boundary to be the Klamath River, which would extend the red tree vole's
range into northwestern California.

The northern extent of the red tree vole's distribution is spotty, with
collection records along the Columbia River at Cascade Locks (Maser
1966, p. 15). The red tree vole has not been found north of the Columbia
River (Verts and Carraway 1998, p. 309). Its distribution in Clatsop and
Columbia Counties in northwestern Oregon is less certain, with a single
specimen recorded from central Clatsop County (Verts and Carraway 1998,
pp. 310, 546). The red tree vole range includes the west slope of the
Cascade mountains (Corn and Bury 1986, p. 405), with the known
eastern-most limit occurring in the Columbia River Gorge at Mitchell
Point, about 2 miles west of Hood River, Oregon (USDA and USDI 2007, p.
289).

Surveys conducted for red tree voles by Federal land management agencies
as part of the Survey and Manage program under the Northwest Forest Plan
have provided additional information on the distribution of the red tree
vole (USDA and USDI 2007, p. 289). These surveys indicate that red tree
voles are uncommon or absent in much of the North Coast Range and North
Cascades of Oregon. Forsman et al. (2004, p. 300) also reached the same
conclusion based on remains of red tree voles in northern spotted owl
(*Strix occidentalis caurina*) pellets, though data were sparse from
these regions as compared to the rest of the red tree vole's range.
Based on surveys, the eastern limit of red tree vole distribution in
southwestern Oregon includes Josephine County and a narrow band along
the western and northern edges of Jackson County (USDA and USDI 2007, p.
289).

Red tree voles are generally restricted to lower elevation coniferous
forests, although a few records of this species above 4,265 ft (1300 m)
have been reported (Manning and Maguire 1999, entire; Forsman et al.
2004, p. 300). Red tree voles may be limited to lower elevations because
their nests don't provide adequate insulation, and foraging along snow
and ice-covered branches may be more difficult (Hamilton 1962, p. 503).

The limits of the range of the dusky tree vole are even less clear than
the red tree vole. Johnson and George (1991, p. 12) describe its range
as restricted to the west slope of the Coast Range in Tillamook and
Lincoln Counties, Oregon. However, Maser (1966, p. 16) summarized
collection and nest records for the dusky tree vole that were from
locations east of the Coast Range crest down to the western edge of the
Willamette Valley in Washington, Yamhill, Polk, Benton, and Lane
Counties. Brown (1964, p. 648) mentions four dusky tree voles collected
near Molalla in Clackamas County. Howell (1926, p. 34) refers to
second-hand information as "unmistakable evidence" of red tree voles
being found in old nests near Bonneville, in far eastern Multnomah
County, and then goes on to say, "Though this sign may possibly have
been of *longicaudus*, it is considered more likely to have been of
*silvicola*." However, he does not describe the "unmistakable evidence,"
nor does he elaborate on why he concluded that it was indicative of the
dusky tree vole. Maser (1966, p. 8) observed that tree voles
historically collected north of Eugene and west of the Willamette Valley
were typically classified as the dusky tree vole, while those collected
north of Eugene and east of the Willamette Valley were almost all
identified as red tree voles.

*Home Range and Dispersal*

The only published data on home range sizes and dispersal comes from red
tree voles radio-collared in the southern Coast Range and southern
Cascades of Douglas County in southwestern Oregon (Swingle 2005, pp.
51-63, 84-89). Of 52 radio-collared red tree voles, 20 had home ranges
consisting of their nest tree and a few adjacent trees, whereas the
remainder occupied up to 6 different nests spaced up to 431 feet (131
meters) apart in different trees (Swingle 2005, p. 52). Home range sizes
did not differ among sexes nor among voles occurring in young and old
forests (Swingle 2005, p. 56). Dispersal distances of subadults ranged
from 10 feet to 246 feet (3 meters to 75 meters) (Swingle 2005, p. 63)

*Habitat*

Red tree voles are primarily and predominantly associated with conifer
forests (Hayes 1996, p. 3) and use a variety of tree species. Red tree
voles are principally associated with Douglas-fir (Jewett 1920, p. 165;
Bailey 1936, p. 195), feeding on Douglas-fir needles and nesting in
Douglas-fir trees. Red tree vole nests have also been documented in
Sitka spruce (*Picea sitchensis*) (Jewett 1920, p. 165), grand fir
(*Abies grandis*), western hemlock (*Tsuga heterophylla*), Pacific yew
(*Taxus brevifolia*), and two non-conifers, bigleaf maple (*Acer
macrophyllum*) and golden chinquapin (*Castanopsis chrysophylla*)
(Swingle 2005, p. 31). While red tree vole nests have been documented in
non-conifers, data indicate their principal diet consists of conifer
needles (Howell 1926, p. 52 (see Diet section for further discussion).
Dusky tree voles in the North Coast Range are also associated with Sitka
spruce and western hemlock forests (Walker 1930, pp. 233-234). While
Booth (1950, as cited in Maser 1966, p. 42) noted that dusky tree voles
live mainly in Sitka spruce and hemlock trees rather than Douglas-fir,
Maser (1966, p. 42) contended that they are not restricted to Sitka
spruce and Douglas-fir habitat based on his data and earlier
observations by Howell (1921) and Jewett (1930, pp. 81-83) as referenced
by Maser (1966, p. 42).

Although it occurs and nests in younger, second-growth forests (Jewett
1920, p. 165; Brown 1964, p. 647; Maser 1966, p. 40; Corn and Bury 1986,
p. 404), the red tree vole tends to be more abundant in older forests
(Corn and Bury 1986, p. 404; Carey 1989, p. 157; Aubry et al. 1991, p.
293). Carey (1991, p. 8) reported that this species seems to be
especially well-suited to the stable conditions of old-growth
Douglas-fir (*Pseudotsuga menziesii*) forests. However, Swingle (2005,
pp. 78, 94) found red tree voles nesting in young forests (22 to 55
years old) as frequently as older forests (110 to 250 years old) and
concluded that young forests may be more important than originally
thought, and perhaps especially critical for tree vole persistence in
areas where old forests have been largely eliminated.

Trees containing tree vole nests are significantly larger in diameter
and height than those without nests (Gillesberg and Carey 1991, p. 785;
Meiselman and Doyle 1996, p. 36 for the Sonoma tree vole). Live,
old-growth trees may be optimum tree vole habitat because primary
production is high and leaves are concentrated, allowing maximum food
availability. In addition, old-growth canopy buffers weather changes and
has high water-holding capacity, providing fresh foliage and a water
source (Gillesberg and Carey 1991, pp. 786-787).

Howell (1926, p. 40) reported that "considerable" expanses of land
without suitable trees are a barrier to tree vole movements. However,
there are a few records of red tree voles captured in early successional
forest stages, such as clearcuts (Corn and Bury 1986, p. 405; Verts and
Carraway 1998, p. 310), and infrequent observations of them crossing
roads (Swingle 2005, p. 79), suggesting that "small forest gaps"
(Swingle 2005, p. 79) may not be much of an impediment to tree vole
movement. The point at which forest gaps become large enough to impede
tree vole movement is not known.

*Reproduction*

Red tree vole litter sizes are among the smallest compared to other
rodents of the same subfamily, averaging 2.9 young per litter (range 1
to 4) (Maser et al. 1981, p. 205; Verts and Carraway 1998, p. 310).
Swingle (2005, p. 71) documented females breeding throughout the year,
with most reproduction occurring between February and September. Red
tree voles are capable of breeding and becoming pregnant immediately
after a litter is born (Brown 1964, pp. 647-648), resulting in females
potentially having two litters of differently aged young in their nests
(Swingle 2005, p. 71). However, the frequency of breeding and the number
of litters born to a female in a year are unknown. Young tree voles
develop more slowly than do non-arboreal vole species (Howell 1926, pp.
49-50; Maser et al. 1981, p. 205). Tree vole nests are located in the
tree canopies and are constructed from twigs, resin ducts discarded from
feeding, lichens, feces, and conifer needles (Gillesberg and Carey 1991,
p. 785).

*Diet*

Tree voles are unique in that they specialize on conifer needles as
their principal diet, with Douglas-fir needles the primary species
consumed (Howell 1926, p. 52; Benson and Borell 1931, p. 230; Maser et
al. 1981, p. 205). However, tree voles will consume needles from other
conifers, such as Sitka spruce, western hemlock, grand fir, bristlecone
fir (*Abies bracteata*), and introduced conifers (Jewett 1920, p. 166;
Howell 1926, p. 52; Walker 1930, p. 234; Benson and Borell 1931, p.
229). Walker (1930, p. 234) observed a captive dusky tree vole that
preferred hemlock needles over spruce or fir needles. He also observed
that dusky tree vole nests tended to be constructed of conifer twigs of
the same species of tree in which the nest was located. This led him to
suggest that young dusky tree voles may feed solely on the needles of
the tree in which they live and develop a forage preference for needles
from that conifer species. Tree voles are known to also eat bark,
cambium, and lichen (Wight 1925, p. 283; Maser 1966, p. 144).

Tree voles appear to obtain water from their food and from fog or dew
that forms on conifer needles, lichen, and moss (Maser 1966, p. 148;
Maser et al. 1981, p. 205; Carey 1996, p. 75). In keeping captive Sonoma
tree voles, Hamilton (1962, p. 503) noted that it was important to keep
leaves upon which they feed moist, otherwise the voles would lose weight
and die. This may explain the distribution of tree voles being limited
to more humid forests (Howell 1926, p. 40; Hamilton 1962, p. 503).

*Mortality*

Many different species feed on tree voles, including carnivorous mammals
(Maser 1966, p. 124; Alexander et al. 1994, p. 97; Swingle 2005, p. 69)
and a variety of raptors (Maser 1965; Forsman and Maser 1970; Reynolds
1970; Forsman et al., 1984, p. 40; Graham and Mires 2005, p. 39). Other
documented predators include the Steller's jay (*Cyanocitta stelleri*)
(Howell 1926, p. 60) and the gopher snake (*Pituophis catenifer*)
(Swingle 2005, p. 69). In addition, Maser (1966, p. 164) found evidence
of tree vole nests being torn apart by northern flying squirrels
(*Glaucomys sabrinus*), raccoons (*Procyon lotor*), western gray
squirrels (*Sciurus griseus*) and Douglas' squirrels (*Tamiasciurus
douglasii*), potentially in search of young voles. Swingle (2005, p. 69)
observed weasels (*Mustela* spp.) to be the primary predator of red tree
voles.

Other mortality sources include disease, old age, storms, forest fires,
and logging (Maser et al. 1981, p. 206). Carey (1991, p. 8) claimed that
forest fires and logging are far more important mortality factors than
predation in limiting vole abundance.

Factors Affecting the Species

Section 4 of the Act (16 U.S.C. 1533), and its implementing regulations
at 50 CFR 424, set forth procedures for adding species to the Federal
Lists of Endangered and Threatened Wildlife and Plants. A species may be
determined to be an endangered or threatened species due to one or more
of the five factors described in section 4(a)(1) of the Act: (A) the
present or threatened destruction, modification, or curtailment of its
habitat or range; (B) overutilization for commercial, recreational,
scientific, or educational purposes; (C) disease or predation; (D) the
inadequacy of existing regulatory mechanisms; or (E) other natural or
manmade factors affecting its continued existence. In making this
finding, we evaluated whether information on threats to the red tree
vole and the dusky tree vole presented in the petition and available in
our files at the time of the petition review constitute substantial
scientific or commercial information such that listing the species may
be warranted. Our evaluation of this information is discussed below.
Unless clearly stated that the information is from our files, all
threats described below and their effects on the red tree vole and the
dusky tree vole are as described in the petition.

*A. Present or Threaten**ed Destruction, Modification or Curtailment of
the Species' Habitat or Range*

According to the petition, tree voles depend on trees for their survival
and are considered to have the narrowest niche of all arboreal mammals
in the Pacific Northwest (Carey 1996, p. 75). Our files indicate that,
while primarily dependent on older Douglas Fir, they are secondarily
capable of using several tree species and younger stands. They are
considered among arboreal mammals to be the most vulnerable to habitat
loss and fragmentation (Huff et al. 1992). Due to their low mobility and
poor dispersal capability, tree voles are unable to respond to loss of
forests from logging (Maser et al. 1981; Carey 1989, 1991; Hayes 1996)
and other habitat-removing disturbances such as development (USDA AND
USDI 2000), recreation, and roads. Maser et al. (1981, p. 206) claim
that clear-cut logging has nearly eliminated entire tree vole
populations in many areas and is responsible for local population
disappearances and the widely scattered population distribution that
currently exists. The petitioners assert that low reproductive rates do
not allow tree vole populations to bounce back as readily from declines.
The petitioners also state that based on the tree vole's association
with old-growth forest and the loss of that habitat through timber
harvest, fire, and other disturbances, the historical distribution of
the species was likely more extensive than it is today (USDA AND USDI
2000). As tree vole populations are reduced and become more isolated,
inbreeding becomes a threat if genetic interchange does not occur (USDA
AND USDI 2000).

As described in the petition, although primarily associated with
old-growth forest, tree voles have also been found in young forests
(Maser 1966; Corn and Bury 1986; Gillesberg and Carey 1991; Swingle
2005) in association with structural complexity such as tree
deformities, increased canopy cover, interconnected tree crowns, broken
tops, or dense limb whorls. In landscapes where old forests have been
mostly eliminated, such stands may play an important role in dispersal
and persistence of tree vole populations (Swingle 2005, p. 94).
Consequently, both old-growth and younger forests with structural
complexity may play key roles in regards to the species' persistence.

The petitioners claim that most of the land within the range of the
dusky tree vole is managed for timber production, with 28 percent
managed by the Oregon Department of Forestry at the Clatsop and
Tillamook State Forests, 41 percent owned and managed by private timber
industry, 11 percent owned by other private entities, and 16 percent
administered by the Forest Service and the Bureau of Land Management
(BLM). Timber harvest through clearcutting and thinning, as well as
intensive forest management practices that include short rotations and
even-aged, single-tree species plantations, have significantly reduced
and isolated tree vole populations, increasing their risk of extinction
(USDA and USDI 2000). Moreover, unlike other red tree vole populations,
the dusky tree vole forages on the needles of spruce and hemlock trees.
Replanting following logging and fire has resulted in the conversion of
many spruce and hemlock stands in the range of the dusky tree vole to
single-species plantations of Douglas-fir, dramatically altering the
species' forage base.

The petitioners contend that habitat of the red tree vole, inclusive of
the dusky tree vole, is also threatened by the development of homes,
hotels, and resorts in western Oregon, particularly on the Oregon coast.
Given the infrequent observations of tree voles crossing roads, the
petitioners believe that existing roads continue to fragment tree vole
habitat and isolate populations. Human population growth in western
Oregon has been rapid in the past 100 years and is expected to continue
at a rate above the national average (ODF 2001). Between 1990 and 2000,
human populations in Clatsop and Tillamook Counties grew by 7 percent
and 12.5 percent, respectively (U.S. Census Bureau 2006). Tourism is a
significant component of the economy in the north Oregon coast area,
bringing with it a demand for more development such as resorts, hotels,
restaurants, and recreation (ODF 2001).

The petitioners assert that old-growth forest habitat loss and
fragmentation has substantially impacted and reduced the distribution
and abundance of the dusky tree vole in all of its range and the red
tree vole throughout its range in western Oregon. Information in our
files is consistent with this assertion, although we also acknowledge
that both old-growth and younger forests with structural complexity may
play key roles in regards to the species' persistence.. Therefore, we
conclude that the petitioners have presented substantial information to
indicate that the present or threatened destruction or modification of
habitat or range may present a threat to the dusky tree vole in all of
its range and the red tree vole throughout its range in western Oregon.

*B. Overutilization for Comme**rcial, Recreational, Scientific, or
Educational Purposes*

Neither the petition nor information in our files presents information
indicating that overutilization of red tree voles, inclusive of the
dusky tree vole, for commercial, recreational, scientific, or
educational purposes is a threat.. Therefore, we find that the petition
does not present substantial information to indicate that the
overutilization for commercial, recreational, scientific, or educational
purposes may present a threat to the dusky tree vole in all of its range
or the red tree vole throughout its range in western Oregon.

*C. Diseas**e or Predation*

Neither the petition nor information in our files presents information
indicating that disease or predation are significant threats to the red
tree vole, inclusive of the dusky tree vole. Therefore, we find that the
petition does not present substantial information to indicate that
disease or predation may present significant threats to the dusky tree
vole in all of its range or the red tree vole throughout its range in
western Oregon.

*D. Inadequacy of Existing Regul**atory Mechanisms*

The petitioners cite USDA and USDI (2000) as the basis for concluding
that most dusky tree vole habitat throughout the north Oregon coast is
owned by private logging companies or is managed by the State to the
extent that there are no specific regulations to protect or enhance the
dusky tree vole as part of their forest management activities. As
discussed above under Factor A, the petitioners assert that existing
forest management in the north Oregon coast area is not conducive to
tree vole persistence because it does not protect sufficient amounts of
older forest used by tree voles.

The petitioners assert that buffer requirements and tree retention
standards on State and private forest lands in the north Oregon coast
area do not provide adequate protection for dusky tree voles. They state
that current tree retention standards do not provide for the maintenance
of sufficient canopy closure needed by dusky tree voles and are not
sufficient to protect individuals or populations. They further note that
riparian buffers may provide some habitat protection, but such areas are
likely to be fragmented and not large enough to support dusky tree vole
populations. Required buffers around the nests of some protected bird
species such as the bald eagle and the northern spotted owl may
incidentally protect some individual voles. However, because nest tree
buffers do not target dusky tree vole populations, cover a small and
fragmented portion of the landscape, and, in some cases, are only in
effect as long as the site is occupied by the target species, the
petitioners conclude that these buffers are unlikely to protect viable
populations of dusky tree voles.

The petitioners assert that requirements on the Tillamook and Clatsop
State Forests to maintain 25 percent older forest structure are
inadequate because they fail to protect existing dusky tree vole
populations and they do not ensure that tree vole habitat is distributed
such that populations will be connected. Rather, under current
regulatory mechanisms, older forest stands will likely occur as
scattered, isolated parcels. Currently, private timber companies and the
State are not funding or conducting dusky tree vole surveys or providing
protection for habitat that is currently occupied.

The petitioners assert that with only 16 percent of the forest land
within the range of the dusky tree vole on Federal land (USDA and USDI
1994, 2000, 2004), protection measures on these lands provide little
benefit to the dusky tree vole or its habitat. All Federal lands in the
north Oregon coast area within the range of the dusky tree vole are
managed as the North Coast Range Adaptive Management Area, of which
nearly 70 percent is managed as Late-Successional Reserves (LSRs).
Although LSRs are managed to maintain and restore late-successional
forest conditions, some thinning and salvage logging activities are
still occurring within them that may impact dusky tree vole populations.
Outside of LSRs, the dusky tree vole receives some protection on Federal
land from the Survey and Manage Program, which requires surveys and
protection of known occupied sites. However, this Program, which is
implemented on Forest Service and BLM lands within the Northwest Forest
Plan area, is scheduled to be discontinued (see discussion below).

The petitioners state that, based on USDA and USDI (2000), over 70
percent of the known occupied sites and 47 percent of the known and
suspected range of the red tree vole (inclusive of the range of the
dusky tree vole) are on Federal lands. Data from our files indicate that
35 percent of red tree vole habitat, (inclusive of the range of the
dusky tree vole) on Federal land in Oregon is in a reserve allocation on
Federal lands (e.g. LSRs, Wilderness Areas and other Congressionally and
administratively withdrawn areas), and 27 percent of the known and
suspected range of the species, across all ownerships, is in reserve
land allocations (USDA and USDI 2000, pp. 385-386). However, the
petitioners cite the USDA and USDI (2000, p. 386) as the basis for
concluding that only about 34 percent of the land base in reserve
allocations is in an older age condition that provides good tree vole
habitat.

Outside of Federal lands, the petitioners assert that, like the dusky
tree vole, the red tree vole is not adequately protected by existing
regulatory mechanisms on private lands where clearcut logging, heavy
thinning, and short rotations are the primary silvicultural activities.
The petition concludes that there is little State-owned land in central
and southern Oregon such that State land management will have little
effect on red tree voles.

The petition notes that the red tree vole, inclusive of the dusky tree
vole, is vulnerable to the impacts of logging because of its dependence
on trees for food and shelter, its limited dispersal ability, and low
reproductive rates (Maser et al.1981; Carey 1991; USDA and USDI 2000).
Although red tree vole populations outside the range of the dusky tree
vole are larger than the dusky tree vole population, local populations
of the red tree vole are small and isolated (USDA and USDI 2000). The
greatest amount of logging in Oregon over the next 50 years is projected
to occur in the southern portion of the red tree vole's range, where it
is considered the most widespread (USDA AND USDI 2000; Haynes 2003, in
Zhou et al. 2005). In addition, a recent settlement agreement between
the Bureau of Land Management (BLM) and counties in western Oregon could
lead to a substantial increase in logging throughout western Oregon.

Our files indicate that since we received the petition, the Forest
Service and the BLM have signed Records of Decision to eliminate the
Survey and Manage Guidelines throughout the range of the red tree vole,
which includes the range of the dusky tree vole (USDA 2007; USDA and
USDI 2007; USDI 2007). Although the dusky tree vole would be included
under the Forest Service and BLM Special Status Species Program (SSSP)
in the North Coast Range (USDA AND USDI 2007), the petitioners did note
before the Survey and Manage Program was discontinued that the SSSP will
not have a substantial impact on the protection and recovery of the
dusky tree vole because of limited Federal ownership and because survey
and mitigation measures under the SSSP program are optional. As part of
its Record of Decision to discontinue the Survey and Manage program, the
Forest Service did add mitigation measures requiring pre-project
clearances and managing known red tree vole sites in the north Cascades
range (north of Highway 22) because of limited habitat in this area
(USDA 2007); this area does not include the range of the dusky tree
vole, as described by the petitioners. While the Forest Service and BLM
have signed decision documents discontinuing the Survey and Manage
program, their ability to implement those decisions has been challenged
in court (*Conservation Northwest, et al.* v. *Mark E. Rey, et al.*, No.
C-04-844P).

The petition asserts that much of the red tree vole's habitat in Oregon,
inclusive of the range of the dusky tree vole, is not subject to
adequate, current regulatory mechanisms that protect it from loss and
fragmentation. The petitioners note that only a portion of current tree
vole habitat in Oregon is protected on Federal lands within reserves
established under the Northwest Forest Plan. Information in our files is
consistent with these assertions in that we note 35 percent of red tree
vole habitat, (inclusive of the range of the dusky tree vole) on Federal
land in Oregon is in a reserve allocation on Federal lands, with the
remaining 65 percent subject to possible land disturbing activities. For
these reasons, we conclude that the petitioners have presented
substantial information to indicate that existing regulatory mechanisms
may be inadequate to protect the red tree vole throughout its range in
western Oregon, inclusive of the range of the dusky tree vole.

*E. Other Natur**al or Manmade Factors Affecting the Species' Continued
Existence*

The petitioners noted fire, population size, genetic isolation, and life
history traits as threats in this category. The specific life history
traits included narrow habitat requirements, low mobility, low dispersal
ability, and low reproductive potential. As these traits were addressed
above in sections discussing previously mentioned threats and no new
information was presented by the petitioners for this threat category,
the previous discussions are not repeated here.

The petition notes that, while the fire regime of the North Coast Range
of Oregon is infrequent, with fires occurring at intervals of 300 to 400
years, the fires that do occur tend to be stand-replacing (Agee 1993;
ODF 2001). High-severity fires have a similar impact on red tree voles
as logging by removing trees and directly impacting populations (Carey
1991, p. 8). In addition, the proliferation of even-aged, high-density
single species plantations resulting from clearcutting may be increasing
fire risk because such areas more effectively carry fire than
uneven-aged stands (USDA and USDI 1994; DellaSalla et al. 1995; Morrison
et al. 2000).

The petitioners assert that small, isolated populations of the dusky
tree vole place the species at risk of extirpation because of inbreeding
depression and demographic and environmental stochasticity (USDA and
USDI 2000), leading to irreversible population crashes (Lehmkuhl and
Ruggiero 1991, p. 37). Low numbers of dusky tree vole sites and low
abundance at known sites indicate the species numbers may be at
dangerously low levels (USDA and USDI 2000, 2003; Forsman et al.2004;
ONHIC 2004). Stochastic events that put small populations at risk of
extinction include variation in birth and death rates, fluctuations in
gender ratio, inbreeding depression, and random environmental
disturbances such as fire, wind, and climatic shifts (Gilpin and Soule
1986). Genetic inbreeding due to small, isolated populations may already
be occurring as evidenced by the occurrence of cream-colored and
melanistic tree voles (Swingle 2005). The petitioners assert that
because dusky tree vole populations are already isolated, declining
populations will not be rescued through genetic interchange and
population augmentation. In addition, the petitioners assert that due to
narrow habitat requirements, low reproductive rates, and low mobility,
dusky tree voles are at an increased risk of extirpation because they
are from small populations that are especially vulnerable to
anthropogenic and stochastic events (Maser et al.1981; Carey 1991; USDA
and USDI 2000).

The petition asserts that the dusky tree vole may be threatened by
intrinsic population factors that make it especially vulnerable to
anthropogenic and stochastic events. Information in our files relative
to the potential impacts of stochastic events on small populations is
consistent with this assertion. For these reasons, we conclude that the
petitioners have presented substantial information to indicate that
other natural or manmade factors may be affecting the continued
existence of the dusky tree vole.

Finding

We have reviewed the petition, supporting information provided by the
petitioner, and information in our files, and we evaluated that
information to determine whether the sources cited support the claims
made in the petition. Based on this review, we find that the petition
presents substantial information indicating that listing one of the
following three entities as threatened or endangered may be warranted:
(1) the dusky tree vole subspecies of the red tree vole; (2) the north
Oregon coast DPS of the red tree vole, whose range corresponds to that
of the dusky tree vole; or (3) the red tree vole in a significant
portion of its range. This conclusion is based on information that
indicates the species' continued existence may be affected by loss and
fragmentation of old-growth forest habitat from timber harvest,
development, and roads (Factor A); inadequate protection from threats by
regulatory mechanisms (Factor D); and other natural or manmade factors
such as increased fire severity, small population size, and genetic
isolation (Factor E). The petition did not contain information
indicating that Factors B and C are considered a threat to this species.
As a result of this finding, we are initiating a status review of the
species, including an evaluation of the north Oregon coast population of
red tree vole and the red tree vole throughout its range. At the
conclusion of the status review we will issue a 12-month finding, in
accordance with section 4(b)(3)(B) of the Act, as to whether or not the
Service believes a proposal to list the species is warranted.

We have reviewed the available information to determine if the existing
and foreseeable threats pose an emergency. We have determined that
although there are apparent threats to the species, they do not appear
to be of such a magnitude as to pose an immediate and irreversible
threat to the species such as to warrant emergency listing at this time.
However, if at any time we determine that emergency listing of the dusky
tree vole is warranted, we will seek to initiate an emergency listing.

References Cited

A complete list of all references cited herein is available, upon
request, from the Oregon Fish and Wildlife Office (see FOR FURTHER
INFORMATION CONTACT).

Author

The primary author of this notice is the staff of the Oregon Fish and
Wildlife Office (see FOR FURTHER INFORMATION CONTACT).

Authority

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

Dated: \_\_\_\_[October 17,
2008]{.underline}\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_

\_\_\_\_[/s/ Kenneth Stansell]{.underline}\_\_\_\_\_\_\_\_\_\_\_\_\_

Acting Director, U.S. Fish and Wildlife Service.

Billing Code 4310-55-P