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NATIVE AND NONNATIVE RED FOXES
370
review of native and nonnative red
North America
foxes
Jnn E Knmler and Warrea B. Bnllard
Abstract Native and nonnative red foxes (Vulpes vulpes) reportedly occur in North America,
although the origin and taxonomy of many populations often are unknown and disputed.
To help elucidate the origin and taxonomy of red fox populations in North America, we
conducted a literature review that focused on the historical distribution of native red
foxes, known populations of nonnative red foxes, range expansions during the 1900s, taxonomic and ecological differences between native and nonnative red foxes, and impacts
of nonnative red foxes on native species. Our review indicated that native red foxes are
a boreal species that historically occurred in the northern regions of North America and
in the southern refugia ot' montane habitats at higher elevations throughout the western
United States. Nonnative red foxes, from European origin, were introduced throughout
the eastern United States and in lowland areas in the Pacific coast states. From a source
population in the eastern United States, red foxes expanded westward throughout the
central United States and Canada during the 1900s, indicating that these red foxes were
nonnative. Nonnative red foxes thrive in human-altered habitats such as urban and agricultural areas and have invaded diverse ecosystems ranging from desert to arctic tundra.
Nonnative red foxes have negative impacts in many ecosystems where they now occur
because they are generalist predators that attain relatively high densities. Nonnative red
foxes likely replaced native red foxes throughout all northern boreal regions and may
threaten remaining native populations at higher elevations in the western United States.
The taxonomy of red foxes in North America needs to be re-evaluated. Although native
and nonnative red foxes in North America are considered conspecifics, there are substantial differences in coloration, morphology, behavior, and habitat requirements
between these 2 types.
Key words distribution, native red fox, nonnative red fox, range expansion, taxonomy, Vulpes vulpes
Red foxes (Vulpes vulpes) are common predators that occur throughout much of North America.
Both native and nonnative red foxes reportedly
occur in North America (Churcher 1959, Aubry
1983, Crabtree 1993, Lewis et al. 1999), although
the origin and taxonomy of many populations are
unknown and disputed. Native red foxes reportedly are a cold-adapted species that occurs in boreal
and montane habitats, whereas nonnative red foxes
reportedly are a generalist species that occurs in a
wider variety of habitats (hubry 1983, Crabtree
1993). The taxonomy and distribution of red foxes
has been reviewed for the eastern United States
(Churcher 1959) and the Pacific Coast states
(Aubry 1984, Lewis et al. 1999). Churcher (1959)
found that native red foxes did not historically
occur in the mixed hardwood forests of the eastern
United States. Due to the absence of native red
foxes in this region, early settlers began releasing
European red foxes for sport hunting in the mid1700s (Churcher 1959, Godin 1977). This population of nonnative red foxes was augmented by
other intentional releases over the next 150 years.
thus establishing a continuous population across
Authors address: Department of Range, Wildlife, and Fisheries Management, Texas Tech University, Box 42125, Lubbock, TX
79409, USA;e-mail for Kamler: [email protected].
Wildlife Society Bulletin 2002, 30(2):370-379
Peer refereed
Native and nonnative red foxes
Kamler and Ballard
371
the eastern United States (Churcher 1959). A dis- nonnative red foxes in management programs by
junct population of introduced red foxes was estab- state and provincial agencies. However, it is imporlished in a similar manner during the past 100 years tant that biologists distinguish between native and
along the western coast of the United States from nonnative red foxes in their management practices.
Washington to California (Aubry 1984,Lewis et al. especially if populations of native red foxes are
1999). Red foxes introduced in this region were threatened and consequently need to be protected.
Our objectives were to review the: 1) historical
from the eastern United States (A~ibry1984, Lewis
et al. 1999), indicating they also were descendants distribution of native red foxes in North America,
2) range expansion of red foxes in the central Unitof European red foxes.
Red foxes, from unknown origin, expanded ed States and Canada, 3) taxonomic and ecological
throughout most of the central and western United differences between native and nonnative red
States during the past 100 years (Fichter and foxes, and 4) actual and potential impacts of nonWilliams 1967, Hoffman et al. 1969,Johnson and native red foxes on native species.
Sargeant 1977.Voigt 1987). Most literature sources
indicated that populations in these regions were
Methods
native red foxes that had recovered from low numWe reviewed historical and more recently pubbers, or had expanded from adjacent regions
(Fichter and Williams 1967,Johnson and Sargeant lished information concerning the range of native
1977. Fitzgerald et al. 1994). Thus, despite a large red foxes in North America. We catalogued referand continuous population of nonnative red foxes ences on a state-by-state and provitlce-by-province
throughout the eastern United States, many biolo- basis to examine the distributional changes and
gists consider red foxes in the central and western range expansion of red foxes during the past 100
United States to be from native origin. Red foxes years in the central United States and Canada. We
that expanded westward throughout the arctic tun- also documented and summarized the taxo~lomic
dra during these same periods were also consici- and ecological differences between native and nonered to be of native origin (Marsh 1938, MacPher- native red foxes. From our review we identified
son 1964).
impacts of nonnative red foxes on native species
Clearly, a review of the origin and taxononly of and ecosystems in the IJtlited States and other areas
red foxes in the central United States and Canada is of the world. Finally,we also obtained recent inforneeded. This information would be valuable to mation concerning livestock depredations by nonwildlife biologists, as management decisions and native red foxes in western states.
conservation efforts could be based on whether
red foxes were native fauna or introduced predaResults
tors. If nonnative red foxes do occur throughout
the central United States and Canada, their poten- Historical distribution of native red
tial to negatively affect native prey species might be foxes in North America
great. For example, nonnative red foxes have
Prior to European settlement, native red foxes
caused severe declines or extinctions of native occurred in the boreal forests of Canada and northfauna, including threatened and endangered ern ITnited States and in the southern refugia of
species,in several regions of the world (Brockie et montane habitats in the western United States
al. 1988. Strahan 1995, Dickman 1996, Lewis et al. (Churcher 1959.A~ibry1983.Crabtree 1993.Figure
1999). If negative impacts of nonnative red foxes 1). Subspecies of native red foxes likely were
are occurring, or could potentially occur in the cen- derived from 2 different ancestral populatiotls
tral United States and Canada, control measures (Aubry 1983) The subspecies that occur in monmay be needed to prevent or lessen the damage of tane habitats in the weqtern United States (i.e . Vr!
tlonnative red foxes on native species.
casc~~densis,
ti zt macrour-a,and V L: necatol-) likely
Little is known about the ecology and distribu- were derived from populations of red foxes that
tion of native red foxes in the western United States occurred south of the Wisconsi~lglaciers during the
because they occur in low densities at high eleva- Pleistocene. When these glaciers retreated
tions, are sensitive to human activities, and have 10-12.000 years ago, those subspecies became
received little study (Aubry 1983, Crabtree 1993). restricted to the southern refugia of montane habiNative red foxes often are not distinguished from tats at higher elevations (Aubry 1983). These sub-
372
Wildlife Socieg Bulletin 2002.30(2):370-379
Figure 1. Probable distribution of subspecies of native red
foxes (Vulpes vulpes) in North America prior to European settlement, based on information primarily from Churcher il9593,
Hall and Kelson (1959), MacPherson (19641, and Aubry (1 983).
Letters represent different subspecies: A = L! v. aiascensis, B =
1! v. abeitorom, C = C: .!L cdscadensis, D = L! v. necator, E = \i
v. macroura, F = L! v. rigalis, and G = C: v. rubricosn. Crossed
diagonal lines indicate populations of C: v. rigalis that were
extirpated by 1900 dones 1964, Dekker 1973, Johnson and
Sargeant 1977).
species are n~orphologicall~~
the smallest, show no
clinal ~~ariations,
and do not intergrade geographically with the other subspecies (Aubry 1983). The
subspecies that occurred throughout the boreal
forests of northern North America, primarily K v.
alnscensis, K v. nbietorum, K L! rigalis, and R 2:.
rubricosn. likely were derived from populations of
red foxes that spread south from Beringia after the
Wisconsin glaciers retreated, although some southderived populations may have integrated with
north-derived populations in the extreme northern
Lhited States (Aubrj 1983). These subspecies show
a clinal variation with decreasing size from the
northwest to the southeast portion of their range
(Churcher 1957,Aubry 1983).
Based on historical records, native red foxes (Re).
rigalis) extendecl south~vard from the boreal
forests into the northern Great Plains (Hoffman
1877,Johnson and Sargeant 1977), as far south as
central Nebraska aones 1964 Figure 1). Although
there is no fossil evidence (Baird 1857), the presence of red foxes in the northern Great Plains was
based on historical records of red fox specimens
from the region. During the Lewis and Clark expedition, 1803-1806, red foxes were reported in the
northern plains near Fort Mandan in central North
Dakota. Fourteen red fox pelts were sent to Wash-
ington, D.C.in 1805 after their winter encampment
(Burroughs 1961). Red foxes were reported near
Fort Clark in central North Dakota in 1833 by the
explorer Maximilian (Bailey 1926) and were
reported by Hoffman (1877) in north-central Somh
Dakota. Red foxes were reportedly trapped as far
nJest as the pine (P~MZIS
spp.) forests in northwestern South Dakota wisher 1914). South-central
Nebraska appeared to be the soutl~ernextent of red
foxes in the Great Plains, as red fox specinlens were
reported from eastern and south-central Nebraska
from the 1820s to 1870s (Jones 1964). In general,
south-central Nebraska was the historical southern
limit for many mammalian boreal species in the
central United States @rey 1992). A few sightings
of red foxes occurred in more southern areas of the
Great Plains during the 1800s, including western
Kansas (Zumbaugh and Choate 1985) and southern
Oklahoma (Caire et al. 1989). However, these sighti n g ~should be used with caution because during
the mid-1800s the name "common red fox" was
interchanged with "grey fox" to describe C'rocyo~z
cinereoarge?ztezcs,as was done during the Lewis
and Clark expedition (Burroughs 1961). The tern1
"large red fox" was used to describe VuQes vulpes
in these cases (Burroughs 1961). Without specimens, the occurrence of red foxes in more western
and southern areas of the Great Plains cannot be
confirmed.
Native red foxes in the northern Great Plains
occurred at Ion7 densities and apparently were sensitive to human activities (Dekker 1973). Consequently, native red foxes disappeared from southcentral Canada to Nebraska by the late 1800s as this
area became settled (Jones 1964, Dekker 1973,
Wrigley 1974,Johnson and Sargeant 1977 Figure 1).
Range expansion across tbe central
United States and Canada
Red foxes began to expand sitnultaneously from
the southeast and east across the central tier of
states in the early 1900s (Figure 2). From the 1900s
to 1920s, red foxes from populations farther east
expanded into areas where they never occurred
historically, including east-central Texas (Strecker
1926. Taylor and Davis 194'), eastern Oklahoma
(Cross 1917), eastern Kansas (Kellogg 1915, Dice
1923, Lindsdale 1928), and southeastern Nebraska
(Swenk 1908). This expansion continued westward
into the 1930s,when red foxes expanded into eastern North Dakota (Johnson and Sargeant 1977).
southern Manitoba (Bird 1961,Soper 1961).central
Native and nonnative recl foxes
Kamler and Ballard
373
Game and Fish, unpublished data). During the
1980s. red foxes expanded throughout lom7land
areas in Utah and Nevada ('J. E Kamler,Texas Tech
UniversiQ unpublished data) In all cases. expansion of red foxes in individual states and provinces
occurred from east to west.
Although red foxes now occur throughout tundra habitats of northern North America (Hall and
Kelson 1959),they did not occupy those areas historically (Marsh 1938, MacPherson 1964). Beginning in the 1910s,red foxes began expanding into
the arctic tundra in northeastern Canada (MacPherson 1964). Over the next 50 jears, this expansion
progressed westward across the northern tundra
(Marsh 1938, hlacpherson 1964) in concert with
the range expansions farther south in the central
United States. Bj the 1960s,red foxes occupied the
entire Baffin Island,southern Elleslncre Island,and
the mainland northwest of Hudson Bay (Marsh
1938, MacPherson 196+). Red foxes eventually
became conlmon in these areas (MacPberson
1964).
Dz~etfleizcesbetuleen native and
nonnative red foxes
Native and nonnatibe foxes in the western United States differ in morphology and ecologj-. There
are 3 major color phases of red foxes found
throughout the world: red, silver (or black), and
cross (Bailey 1936, Durrant 1952, Churcher 1959,
Hall and Kelson 1959.Henrj 1996). The red color
phase is typical of red foxes throughout most of the
Oklahoma (Blair 1939),and central Kansas moost- Old World (Lloyd 1975,L70igt1987) and of nonnaer 1931). In the 1950s. red foxes continued to tive red foxes in the LTnited States (Bailey 1936.
expand westward into western Oklahoma,exclud- Churcher 1959, Aubry 1983). In contrast, color
ing the Panhandle (Glass and Halloran 1960),west- phases other than red are typical of native red foxes
ern Kansas (Anderson and Nelson 1958.Janes and in North ,herica. Most native red foxes (Rr: necnGier 1966, Zumbaugh and Choate 1985), western to?,)from the Sierra Nevada hlountains of California
Nebraska (Jones 1964), western North Dakota and Nevada exhibit the cross and silver color phas('Johnson and Sargeant 1977), and southeastern es (Grinnell et al. 1937, Hall 1946). Similarly,most
Saskatchewan (Stoudt 1971). In the 1960s red native red foxes from higher elevations in and
foxes expanded into west-central Texas (Packard around Yellowstone National Park exhibit the cross
and Bon-ers 19'0). eastern Colorado (Armstrong color phase (Crabtree 1993). The different color
1972), eastern Idaho (Fichter and Williams 1967), phases of red foxes in mountainous areas were also
eastern Montana (Hoffnlann et al. 1969),and south- reported during the Lewis and Clark expeclition
(1803-1806). as Lewis observed a cross phase and
western Saskatchewan (Dzubin and Gollop 19'2),
nr1lerethey never had been previously reported. In silver phase red fox in the higher elevations of
the 1970s,red foxes expanded into southern Alber- western Montana and Oregon. respectively (Burta where. they had been absent since 1900 (Dekker roughs 1961). Of native red foxes that exhibit the
1973), the Oklahoma Panhandle (Hatcher 1982), red color phase, including Kzl. cascadelzsis and Y u .
western Texas (Swepston 1980), and eastern New macrourn, most exhibit a pale red or pale yellowMexico (G. Schmitt, New Mexico Department of ish color (Merriam 1900, Bailey 1936, Read and
Figure 2. Known distribution ancl westward range expansion of
nonnative red foxes (Vulpes vulpesj in central and western
North America at various periods during the past century (See
Results for references of individual states and provinces!. A
similar and concurrent westward range expansion occurred
throughout the arctic tundra (~LlacPherson1964).
374
W'ilcll~eSociep Bulletin 2002.30(2):370-379
Gaines 1914, Fichter and Williams 1967, Aubry
198.3,Hoffmeister 1986), designated as "light" color
phase by Bailey (1936). In contrast, nearly all Old
World and nonnative red foxes exhibit a dark red or
cherry recl color (Obbard 1987). Morphologically,
nonnative red foxes in the western United States
are larger than native red foxes, although some
overlap in size occurs (Aubry 1983).
In the western United States, color phase appears
to be somewhat reliable for distinguishing between
native and nonnative red foxes. However, since
overlap in color occurs, a better method for distinguishing between native and nonnative red foxes
relies on elevational differences (Aubry 1983, Lewis
r t al. 1999). It1Washington.native red foxes (Vz! cnscadensis) and nonnative foxes were restricted to
high- and low-elevation areas, respectivel?; and their
ranges clid not intergrade (Aubry 1983). Similarly,
native (V r ! rzecator) and nonnative red foxes were
separated by elevational differences in California
(Le\\ is et al. 1999). Thus, locations at high elevations, sucl~as subalpine meadows and parklands, are
characteristic of native red fox habitats, whereas all
othcr locations at low elevations, such as agriculture, rangeland. and urban areas, are characteristic of
nonnative red fox habitats. In addition to their more
restricted requirements, native red foxes occur at
relatively low densities (Aubry 1983. Crabtree
1993). which may contribute to the lack of specimens and information concerni~lgthese subspecies.
In contrast, nonnative red foxes occur at relatively
high densities (0.5-1.0 red fox/km2 [Sargeant 1972,
Voigt 19871) in many areas throughout their range.
Inzpacts of nonnative red foxes
The negative effects of nonnative red foxes on
native prey populations can be significant. In Australia, nonnative red foxes. also of European origin,
were introduced in the 1860s for sport and to control tlonnative rabbit ( O ~ ~ ~ c t o lczi~liculzu)
a g ~ ~ s populations (Strahatl 1995. Dickman 1996). These red
foxes, n7hich expanded throughout most of ALEtralia by the 19.30~~
had severe negative impacts on
native species and ecosystems. Nonnative red
h x e s eliminated remnant populations of some
rodent and marsupial species on the mainland. and
e\.idence suggested they were the primary cause in
the decline or extinction of many other small and
meclium-sized rodent and n~arsupialspecies (Strahan 1995. I>ickman 1996). Consequently concentrated control measures for red foxes on the mainland have resulted in the direct resurgence of 7
species of marsupials, including 5 endangered
species (Strahan 1995).
In North America, the negative impacts of nonnative red foxes on nesting ducks in the prairie pothole region has been well documented (Sargeant et
al. 1984, Johnson et al. 1989). Lewis et al. (1999)
indicated there were 24 threatened and endangered species that were vulnerable or potentially
vulnerable to nonnative red foxes in California.
Consequently, nonnative red foxes are controlled in
California to protect the nesting grounds of several
endangered species of birds (Lewis et al. 1999).
Nonnative red foxes have just recently expanded
into the Great Basin region, and because of heavy
predation they are already reducing populations of
pheasants (Phnsinnus colchicus), (Frey et al. 2000),
sage grouse (Centmcerciu zirophasiatzus), (Bunnell et al. 2000), and nesting ducks (S. N. Frey, Utah
State University unpublished data). Control measures have been initiated to reduce nonnative red
fox damage in this region as well (Bunnell et al.
2000, Frey et al. 2000). Evidence suggests that nonnative red foxes could negatively impact endangered San Joaquin kit foxes (t'ulpes ~~zncrotis
mutien), (Ralls and White 1995) and possibly swift foxes
(Vvelox). a species recently petitioned to be listed
as threatened (Sovada et al. 1998).
Nonnative red foxes also prey on livestock. Of all
United States Department of Agriculture (USDA)
Wildlife Services' clients nationwide in 1998, red
foxes were responsible for 1%)of sheep, 5%of lamb.
2% of goat, and 9%)of kid losses to predators (1999
Livestock Wildlife Damage Susvey Results, USDAWildlife Services, unpublished report). Nonnative
red foxes are also a health threat to humans and
pets through transmission of disease, such as rabies,
distemper, parvo virus, and mange (Carey 1982,
Voigt 1987, Davidson et al. 1992. Lewis et al. 1999).
This threat is likely to increase as populations of
nollnative red foxes continue to expand and invade
more urban areas (Lewis et al. 1999).
Discussion
Red foxes that expanded westward across the
central United States and Canada during the 1900s
were likely nonnative, as the source of this expansion came from populations of nonnative red foxes
in the eastern United States. Previous researchers
have found that nonnative red foxes occurred
throughout the lower elevations of Oregon. California, and Washington, whereas native red foxes
Native and nonnative red foxes
Kamler and Ballard
375
occurred in limited areas at higher elevations in the central United States and southern Canada
those states (Aubry 1983,Lewis et al. 1999). Similar exhibited the red color phase (Obbard 1987.Voigt
relationships might occur among native and non- 1987), which was typical of nonnative red foxes
native red foxes in other mountainous western from European origin.
Previously, researchers hypothesized that newly
states, as red foxes now occur throughout these
states at both high and low elevations (Fichter and established red foxes in the northern Great Plains
Williams 1967, Hoffmann et al. 1969, Clark and were native red foxes (Vz: rigalis) that had recovStromberg 1987, Fitzgerald et al. 1994). However, ered from low populations or reoccupied parts of
red foxes in these areas are usually not distin- their former range (Johnson and Sargeant 1977,
guished as native or nonnative. For example,in Col- Jones et al. 1983). For example, Johnson and
orado, Idaho, and Montana, native red foxes (8v. Sargeant (1977) suggested that reductions in cojnzacmum) occur at higher elevations,although red ote (Cavzis latrans) populations after 1915 allowed
foxes recently expanded throughout lowland areas native red fox populations to recover in the northof those states (Fichter and Williams 1967, Hoff- ern Great Plains However, 20 years occurred
mann et al. 1969.Armstrong 1972, Fitzgerald et al. between reduced coyote populations and the reap1994). Fichter and Williams (1967) and Fitzgerald pearance of red foxes (Johnson and Sargeant 1977),
et al. (1994) were unsure of the taxonomy of the suggesting that they were not related events. If
"new"lowland red foxes and suggested classifying native red foxes reoccupied their former range in
them as Vz! rnacroura or Vv, rigalis. Similarly pre- the northern Great Plains, then expansion should
vious researchers correctly classified red foxes in have occurred from the nearest source populations
the mountains of western Wyoming as V 21. found in the boreal forests of Canada and northern
nzacmura but classified red foxes in low elevations Great Lakes region, or the montane habitats at highof eastern Wyoming as Kv. rigalis (Long 1965,Clark er elevations in the western United States. This did
and Stromberg 1987). Our review, along with oth- not occur, as red foxes expanded across the northers (Aubry 1983,Crabtree 1993,Lewis et al. 1999), ern Great Plains from east to west. Furthermore,
suggests that red foxes in lowland areas are nonna- native red foxes from western mountains. such as
tive red foxes that have recently expanded through- Vzt nzacroura, have never expanded their range, as
out the western United States.
these are cold-adapted foxes that occur in the
Similarly, red foxes that currently occupy the southern refugia of high alpine meadows (Aubry
northern Great Plains are usually classifled as native 1983, Crabtree 1993). Aubry (1983) indicated that
red foxes (Vzl rigalis, Jones et al. 1983). Although V 21. nzacroum did not occupy low elevations, and
Vz! rigalis occupied portions of the northern Great that valleys at low elevations were barriers
Plains in pre-European times, these red foxes disap- between adjacent populations at higher elevations.
It is also unlikely that native red foxes (Kz! rigalis)
peared completely in the late 1800s when this
region was settled. Beginning in the 1930s, the from northern boreal forests have expanded their
northern Great Plains was occupied by expanding range southward throughout the central United
populations of nonnative red foxes from the east- States. Some mammalian boreal species (all small
ern United States, and these foxes were well adapt- mammals) have expanded southward into the cened to human settlement and human-induced tral United States during this past century (Frey
changes to the environment. Nonnative red foxes 1992); however, this likely did not occur for red
are descendants from European stock and therefore foxes. Range expansions of other mammalian boreare better adapted to human activities, urban areas, al species occurred distinctly in a north-to-south
and human-induced changes to the environment direction (Frey 1992), as expected, whereas range
(i.e.. habitat fragmentation, agriculture). For exam- expansion of red foxes started in the southeastern
ple. Dekker (1973) stated that the new populations United States and occurred in an east-to-west direcof (nonnative) red foxes that had recently expand- tion. This east-to-westexpansion during the past 100
ed into central Alberta were more adaptable and years occurred throughout south-central Canada and
better able to cope with the human-dominated central United States without any north-to-south or
environment than previous populations of (native) west-to-east expansions from nearby source populared foxes (K 2: abeitorum) that disappeared from tions of native red foxes. Furthermore, range expanthat area in the early 1900s. Additionally, >99% of sion of red foxes continued westward throughout
red foxes from populations that expanded across the western Great Plains and lowland areas of the
376
WIIdlIfe Society Bulletin 2002,30(2):370-379
arid Southwest and Great Basin regions, which
were not typical eilvironments for a boreal subspecies. Native red foxes historically did not occur
in these regions, indicating that the new red foxes
were not recovered populations of a boreal subspecies.
Little is known concerning the status of native
red foxes in the higher elevations of the western
United States. Recent evidence suggested that
native red fox populations in these areas have
declined since the 1800s (Aubry 1983, Crabtree
1993). Native red foxes have not been docuine~lted in some areas of the western Vnited States in
>50 years (Durrant 1952). Their status is now complicated by the relatively new occurrence of nonnative red foxes in most lowland areas of the western United States. If native red foxes still occur
over much of the western United States, then their
populations may now be vulnerable to inbreeding
or competition with the more numerous and larger
nonnative red foxes, which can thrive in hurnanaltered habitats. The California Fish and Game
Commission is the only state agency that distinguishes between native and nonnative red foxes in
its management practices. Nonnative red foxes in
lowland areas of California are often controlled to
protect endangered bird species (Lewis et al. 1999),
whereas native red foxes ( V Z L
necntor) in the Sierra Nevada moulltain range are fully protected and
research is being conducted to document their current numbers and distribution (Kucera 1993).
Other state and provincial agencies should have
similar policies, as remaining populations of native
red foxes may be threatened.
Similar to more southern areas, populations of
native red foxes in the northern boreal forests may
also be vulnerable to expanding populations of
nonnative red foxes. Red foxes expanded westward across the northern tundra during this past
century. Similar to differences reported in more
southern areas of North America, MacPherson
(1964) stated that the"newXred foxes in the Northwest Territories were quite different from previous
populations of red foxes. Original populatiolls of
red foxes occurred in low densities and were found
only in the boreal forests in more southern areas of
the region (MacPherson 1964). In contrast. the
"new" red foxes occupied tundra habitats and
attained densities "far in excess of those in the original population" even in the nearby boreal forests
(MacPherson 1964: 140). Additionally, these new
red foxes also occupied small towns, which were
not occupied by the original red fox populations
(Marsh 1938.MacPherson 1964),indicating that the
new red foxes were nonnatives.
In addition to changes in distribution, behavior,
and density a review of red fox color morphs from
Hudson's Bay Company posts over this same period
showed an increase in frequency of the red color
phase (Butler 1945, 1917; Swanson and Johnson
1996), which was typical of nonnative red foxes
from European origin. Consequently.color morphs
of native species, such as black-silver and cross,
decreased throughout northern Canada (Butler
1945,1947;Swanson and Johilson 1996) and disappeared completely from some areas such as eastern
Canada (Haldane 1942). Previously. researchers
hypothesized several different explanations for the
increasing dominance of the red color phase across
Canada, including selective hunting, selective trapping, differential reprochictive success among color
morphs, and dispersal or swamping by red-colored
foxes from farther south (Haldane 1942, Butler
1945. Calhoun 1950, Swanson and Johnson 1996).
Ek hypothesize that the westward range expansion of nonnative red foxes was responsible for
changes in red fox color inorphs across Canada during the past 150 years. Nonlrative red foxes
expanded their range westward throughout the
tundra and northern boreal forests during the same
periods they expanded westward throughout the
lower United States and southern Canada. The
decrease. and in some areas elimination, of native
red fox color morphs suggests that the more
nunlerous nonnative red foxes replaced or
hybridized with native red foxes throughout all or
most of the northern boreal forests during this past
century. If this has occurred, then subspecies of
native red foxes throughout the northern boreal
forests, including Kz:. nlnsce~zsis,Kzj. nbietorzlnz, K
z! rigulis, and V a rz~bricosa,may be extinct.
Nonnative red foxes, a generalist predator, have
caused severe declines and extinctions of native
species on other continents (Strahan 1995. Dickman 1996). In North America nonnative red foxes
prey heavily on native species, iilcluding threatened
and endangered species, in many areas of their
range (Sargeant et al. 1984. Johnson et al. 1989.
Lewis et al. 1999, Bunnell et al. 2000. Frey et al.
2000). Because nonnative red fox populations are
still expanding and increasing in many areas, their
negative impacts on native species may also
increase. Long-tern~effects of nonnative red foxes
on prey populations in many areas are unknown.
Native and nonnative red foxes
Nonnative red foxes have the potential to cause
declines and possible extinctions of native species
on this continent, possibly because many of the
most vulnerable species, such as ground-nesting
birds, did not evolve with this particular subspecies. Cotlsequently, the recent appearance of
nonnative red foxes in these ecosystems ma); lower
the carrying capacity of ground-nesting bird populations, with possible extirpation of some species.
In areas such as the northern Great Plains,the densities of nonnative red fox populations (0.5 red
fox/km2.Sargeant 1972) are likely higher than that
of historic native red fox populations, which
reportedly occurred in low numbers (Jones 1964,
Johnson and Sargeant 197'). Consequently predation rates of nonnative red foxes are higher than
that of any native carnivore species (Johnson et al.
1989). Overall densities of red foxes increased as
nonnative red foxes expanded westward across
northern Canada (MacPherson 1964). also suggesting that nonnative red foxes occurred at higher
densities than native red foxes.
Finall!; the taxonomic status of red foxes in
North America is questionable. Red foxes in eastern and southern United States are classified as V!'u
,firlzzz,although there may be no scientific basis for
this subspecific designation. Because red foxes
classified as Kz! fr~lz!nare likely from European origin, Churcher (1959) and Hall and Kelson (1959)
questioned their subspecific designation. Red
foxes introduced in eastern North America by early
settlers primarily came from Great Britain and
France. I:' r : cl-~tcigrm,
and Scandinavia. K z: i!ulpes
(Churcher 1959). Thus, nonnative red foxes in
North America are likely hybridized forms of reci
foxes from several different Old World subspecies.
These ~lonnativered foxes have now occupied
nearly all of the United States and probably all of
Canada. Nonnative red foxes have recently expanded southward into northern Mexico (Arnaud 1990),
and thus may continue to expand southward
throughout other areas of the New World.
Prior to 1959,red foxes in North America were
classified as IT fzrlzm, a different species than Old
World red foxes. I! z~zdpes.A separate species designation for New World red foxes was based on differences in morphology and coloration from Old
World red foxes. and this distinction was upheld by
several early mammalogists (Bangs 1897, Merriam
1900, Bailey 1936). Churcher (1959) compared
skull morphology and pelt coloration between red
fox specimens in North America with specimens
Kamler and Ballard
377
from Europe and Asia. Churcher (1959) concluded
that there were not sufficient differences between
New World and Old World red foxes to designate a
separate species, and subsequently New World red
foxes were classified as K uulpes. However.
Churcher (1959) apparently was unaware of the
range expansion of nonnative red foxes in North
America that had already occurred. At least 73% of
the North American specimens used by Churcher
(1959) were from regions where nonnative red
foxes had become well established by the 1950s.
Thus, many specimens that presumably represented native red foxes may have been nonnative red
foxes with Old World origin. Clearly, a thorough
review of red fox taxonomy in North America is
needed. More advanced techniques, such as genetic analyses, may prove usefiil for determining the
taxonomy of red foxes in North America.
Acknoulledgments. We thank the personnel
from state and federal agencies and universities that
provided information concerning red foxes,including D. C. Backlund, R. Beach, M. J. Bodenchuk, S.
Fairaizl. S. N. Fre): R. L. Gilliland,R. L. Harrison, G. A.
Littauer. J. D. Perrine, J. Phelps, C. Richardson. W. K.
Smith. M.A. Sovada,and S. Stivers. We also thank S.
Cunningham, C. Jones, and three anonymous
reviewers for helpful comments on this manuscript. C. C. Perchellet and B. Kamler helped produce the figures. This is Texas Tech University,College of Agricultural Sciences and Natural Resources
technical publication T-9-8'6.
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Jan E Kamler (photo) received his B.S. in biology from the University of Kansas and his M.S. in wildlife biology from Kansas
State University. He currently is a doctoral candidate in the
Department of Range, Wildlife, and Fisheries Management at
Texas Tech University. His research interests include the ecology and interactions of carnivores and predator-prey relationships. Warren B. Ballard received his B.S. in fish and wildlife
management from New Mexico State University, his M.S. in
environmental biology from Kansas State University, and his
Ph.D. in wildlife science from the University of Arizona. He
currently is associate professor in the Department of Range,
Wildlife, and Fisheries Management at Texas Tech University.
His professional interests focus on predator-prey relationships
and population dynamics of carnivores and ungulates.
Special editor: Krausman
hd