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, 63919-63926 [E8-25574]

Agencies

• Fish and Wildlife Service
• DEPARTMENT OF THE INTERIOR

[Federal Register Volume 73, Number 209 (Tuesday, October 28, 2008)]
[Proposed Rules]
[Pages 63919-63926]
From the Federal Register Online via the Government Printing Office [www.gpo.gov]
[FR Doc No: E8-25574]


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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.

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SUMMARY: We, the U.S. Fish and Wildlife Service (Service), announce a 
90-day finding on a petition to list the 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 December 29, 
2008.

ADDRESSES: You may submit information by one of the following methods:
     Federal eRulemaking Portal: https://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 https://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 98th 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

[[Page 63920]]

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 https://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.
    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 https://www.regulations.gov, your 
entire submission--including any personal identifying information--will 
be posted on the Web site. 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.
    Information and materials we receive, as well as supporting 
documentation we used in preparing this finding, will be available for 
public inspection on https://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 Sec.  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,

[[Page 63921]]

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; https://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.

[[Page 63922]]

    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 
feet (1300 meters) 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

[[Page 63923]]

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 part 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

[[Page 63924]]

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 Threatened 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 Commercial, 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. Disease 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 Regulatory 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

[[Page 63925]]

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 Natural 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

[[Page 63926]]

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.
 Kenneth Stansell,
Acting Director, U.S. Fish and Wildlife Service.
 [FR Doc. E8-25574 Filed 10-27-08; 8:45 am]
BILLING CODE 4310-55-P