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Quaternary Research 71 (2009) 93?98
Contents lists available at ScienceDirect
Quaternary
.e lIntroduction
The endangered island fox (Urocyon littoralis), a diminutive relative
of the gray fox (U. cinereoargenteus), has been an important apex
predator on California's Channel Islands for millennia (Collins, 1993;
Moore and Collins, 1995; Roemer et al., 2004). While a great deal is
known about island fox ecology, biogeography, and conservation,
questions remain about when and how these animals ?rst colonized
the Channel Islands (Johnson, 1975, 1983; Wenner and Johnson, 1980;
Collins, 1991a; Vellanoweth, 1998; Agenbroad, 2002a). Most research-
ers agree that Native Americans introduced the island fox to the
southern Channel Islands, probably during the middle to late
Holocene (Collins, 1991a,b; Vellanoweth, 1998; Shelley, 2001). Based
partly on reports of fox remains from late Pleistocene sediments of the
Upper Tecolote Formation on Santa Rosa Island, however, foxes were
Recent AMS (Accelerator Mass Spectrometry) 14C dating of the
Upper Tecolote Formation fox specimen to the late Holocene raised
questions about the natural dispersal of foxes to the northern islands
(Shelley, 2001), but several fox bones from San Miguel Island fossil
localities continued to support a possible Pleistocene age for the
origins of the island fox (Guthrie, 1993:409). All the San Miguel
specimens were found on eroded surfaces where faunal remains of
paleontological, archaeological, or recent biological origin could have
become mixed.
To help clarify the origins, antiquity, and evolution of island foxes,
we obtained direct AMS 14C dates for three island fox bones from the
late Pleistocene SanMiguel Island fossil localities (Fig.1). These are the
only known specimens that could predate the earliest de?nitive
evidence for human colonization of the northern Channel Islands,
approximately 13,000 cal yr BP (Johnson et al., 2002).thought to have reached the northern Ch
during the late Pleistocene by rafting across
narrowed by lower sea levels (Wenner and
1991a,b, 1993).
? Corresponding author. Fax: +1 (202)357 2208.
E-mail address: rickt@si.edu (T.C. Rick).
0033-5894/$ ? see front matter. Published by Universit
doi:10.1016/j.yqres.2008.12.003further paleontological, archaeological, and genetic studies (especially aDNA [ancient DNA]) are conducted.
Published by University of Washington.Island ecology
California Channel Islandsmiddle Holocene. However,Article history:
Received 16 February
Available online 18 January 2009
Keywords:
Island fox
Urocyon littoralis
Animal translocation
AMS 14C datinga b s t r a c t
The island fox (Urocyon littoralis) is one of few reportedly endemic terrestrial mammals on California's
Channel Islands. Questions remain about how and when foxes ?rst colonized the islands, with researchers
speculating on a natural, human-assisted, or combined dispersal during the late Pleistocene and/or Holocene.
A natural dispersal of foxes to the northern Channel Islands has been supported by reports of a few fox bones
from late Pleistocene paleontological localities. Direct AMS 14C dating of these ?fossil? fox bones produced
dates ranging from ?6400 to 200 cal yr BP, however, postdating human colonization of the islands by several
millennia. Although one of these specimens is the earliest securely dated fox from the islands, these new data
support the hypothesis that Native Americans introduced foxes to all the Channel Islands in the early to
a natural dispersal for the original island colonization cannot be ruled out untila r t i c l e i n f oh Stafford Research, Inc., 200 Acadia Avenue, Lafayette, CO 80026, USAOrigins and antiquity of the island fox (U
Channel Islands
Torben C. Rick a,?, Jon M. Erlandson b,c, Ren? L. Vellan
Daniel A. Guthrie g, Thomas W. Stafford Jr. h
a Department of Anthropology, National Museum of Natural History, Smithsonian Instituti
b Museum of Natural and Cultural History, University of Oregon, Eugene 97403-1224, USA
c Department of Anthropology, University of Oregon, Eugene, OR 97403-1218, USA
d Department of Anthropology, California State University, Los Angeles, CA 90032, USA
e Department of Anthropology, Humboldt State University, Arcata, CA 95521, USA
f Department of Vertebrate Zoology, Santa Barbara Museum of Natural History, Santa Barb
g Joint Science Department, Claremont Colleges, Claremont, CA 91711-5916, USA
j ourna l homepage: wwwannel Islands naturally
a Santa Barbara Channel
Johnson, 1980; Collins,
y of Washington.cyon littoralis) on California's
eth d, Todd J. Braje e, Paul W. Collins f,
ashington D.C. 20013-7012, USA
CA 93105, USA
Research
sev ie r.com/ locate /yqresContext and background
Divided into northern (Anacapa, Santa Cruz, Santa Rosa, and San
Miguel) and southern (San Clemente, Santa Catalina, San Nicolas, and
Santa Barbara) groups, California's eight Channel Islands range in size
from about 2.6?249 km2. Currently between 20?98 km offshore, the
islands have not been connected to the mainland during the
ted
94 T.C. Rick et al. / Quaternary Research 71 (2009) 93?98Quaternary (Johnson, 1983). During glacial periods of the Pleistocene,
lower sea levels caused the northern islands to coalesce into a single,
larger island (Santarosae), the eastern end of which was only 6?8 km
from the mainland (see Porcasi et al., 1999; Kennett et al., 2008).
Considerably more dispersed and isolated, the southern islands have
remained farther from the mainland and were more dif?cult for
Figure 1. Southern California and the Channel Islands showing the location of directly da
are archaeological specimens dated by Shelley (2001).terrestrial animals to colonize.
Island foxes are about the size of a house cat (Fig. 2), with
subspecies found on all the islands except Anacapa and Santa Barbara
(each ?2.6?3 km2 in area). Other endemic island terrestrial mammals
appear to have been limited primarily to the deer mouse (Peromyscus
maniculatus), western spotted skunk (Spilogale gracilis), western
harvest mouse (Reithrodontomys megalotis), San Miguel Island vole
(Microtus miguelensis), and ornate shrew (Sorex ornatus; Guthrie,
1998; Schoenherr et al., 1999). Pygmy (Mammuthus exilis) and full-
sized (M. columbi) mammoths lived on the northern islands during the
Figure 2. Adult island fox on San Nicolas Island (photo by R. L. Vellanoweth).Pleistocene (Agenbroad, 1998; Thaler, 1998). Mammoths are generally
good swimmers that colonized the islands naturally, while foxes are
poor over-water dispersers (Wenner and Johnson, 1980; Johnson,
1983; Collins, 1991a).
The focus of extensive conservation, including a captive breeding
program, four subspecies of island fox are currently critically
fox specimens and approximate ages (14C yr BP). Tecolote Member, SNI-11, and SCLI-43Cendangered due to predation by golden eagles (Aquila chrysaetos)
and possibly canine diseases (Coonan et al., 2002, 2005; Roemer et al.,
2002, 2004; Clifford et al., 2006). Foxes are omnivorous, consuming
insects, fruits, mice, small reptiles, marine invertebrates, and other
foods, and they prey on deer mice and ground nesting birds (Moore
and Collins, 1995). Island foxes are generally docile, show little fear of
humans, and are easily tamed (Moore and Collins, 1995).
Island foxes played an important role in the spiritual lives of native
Channel Island peoples?the Island Chumash and Tongva (Gabrielino).
Island foxes have been found in numerous archaeological sites, were
likely semi-domesticates or pets, were harvested for their pelts, and
probably served other functions like pest/rodent control (Collins,
1991b). The Chumash and Tongva had extensive exchange networks
with the mainland and islands, including trade of a variety of beads,
subsistence items, other goods, and likely island foxes (Collins, 1991b;
Vellanoweth, 2001; Kennett, 2005).
Despite research at several Channel Island fossil localities (Lipps,
1964; Orr, 1968; Guthrie, 1993, 1998, 2005; Agenbroad, 1998, 2002b;
Thaler, 1998; Agenbroad et al., 2005), foxes are rare or absent in
paleontological deposits, with bones known from just four localities.
The method of accumulation (carnivore dens, owl roosts, etc.) can
in?uence the types of animals found in a fossil deposit. Guthrie
(2005:37?38) suggested that many of the fossil localities he has
analyzed may have been deposited by bald eagles (Haliaeetus
leucocephalus), with at least one historic bald eagle nest known to
contain a small number (n=10) of island fox bones (Collins et al.
2005). The few fossil specimens are all morphologically similar to
modern island foxes with no documented gray foxes or intermedi-
aries. The ?Pleistocene? Santa Rosa fox remains consist of three bones
from one individual now known to date to 1480?1280 cal yr BP
(Shelley, 2001). Once thought to have been lost, there are limited
notes available for these bones.
The other fox remains were recovered from three late Pleistocene
fossil localities (SMI-V-7, V-10, and V-11) on San Miguel Island
(Guthrie, 1993). For SMI-V-7 on Simonton Cove, Guthrie obtained 14C
dates of 25,160?380 and N38,000 14C yr BP for bird (Fratercula sp.)
bones from the surface. For SMI-V-10 on Cuyler Harbor, he reported a
date of 32,143?787 14C yr BP for a bird (Chendytes lawi) bone from the
surface. SMI-V-11 has not been dated but is located near SMI-V-10.
Archaeological sites are located in the immediate vicinity of all three
localities and extensive erosion may have mixed paleontological,
archaeological, and recent biological materials on these surfaces.
Consequently, these San Miguel Island fox remains could date
anywhere from the late Pleistocene (?38,000 14C yr BP) to the Historic
period.
from ?11.6? for the ca. 6400 yr old specimen to ?18.4? and ?19.5?
for the two late Holocene specimens. Several studies have shown that
stable carbon and nitrogen isotopes from bone collagen are a reliable
proxy of general dietary patterns, especially the degree of marine or
terrestrial contributions to the diet (Chisholm et al.,1982; Schoeninger
et al., 1983; Walker and DeNiro, 1986; Goldberg, 1993; Newsome et al.,
2004). The oldest fox specimen in our sample, with a value of ?11.6?,
is enriched in marine carbon and comparable to values obtained from
marine mammals (see Walker and DeNiro, 1986; Newsome et al.,
2004), suggesting the complete proteins this animal consumed came
almost exclusively from marine foods. The other two values (?18.4?
and ?19.5?) suggest a diet considerably higher in terrestrial foods,
and are comparable to land mammal values reported by Walker and
DeNiro (1986) and values reported for twomodern island fox (?18.3?
and ?16.0?) specimens from San Clemente Island (Goldberg,
be
73
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252
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OH
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a ma
95T.C. Rick et al. / Quaternary Research 71 (2009) 93?98Methods
The three San Miguel localities produced a total of nine fox bones
(long bones, vertebrae, and skull fragments) from three individuals
(one at each locality). We selected one relatively large bone from each
locality for AMS dating, including an ulna from locality SMI-V-7 and
femur fragments from localities V-10 and V-11 housed at the Santa
Barbara Museum of Natural History (SBMNH). The bones are generally
well preserved with two of the specimens (SBMNH 138 and 397)
etched and pitted on the surface, probably from being digested by
another animal and/or sand blasting. The bones were sampled and
analyzed at Stafford Laboratories with protocols outlined in Waters
and Stafford (2007); XAD puri?ed collagen was dated from all three
bones. During collagen extraction, protein preservation was similar to
that expected for recent bones rather than Pleistocene material.
Graphite targets were analyzed at the Keck Carbon Cycle AMS Facility
in the Earth System Science Department, University of California-
Irvine.
Results
Calibrated 14C dates for the three island fox specimens range from
ca. 6400 cal yr BP to the Historic period?much younger than the late
Pleistocene dates available for other bones from the same localities
(Table 1). The locality V-7 ulna produced a date of 6120?25 14C yr BP
(6400?6210 cal yr BP; UCIAMS-40173), currently the oldest securely
dated fox from the Channel Islands. The locality V-10 and V-11 femora
were dated to 990?15 14C yr BP (950?800 cal yr BP; UCIAMS-38253)
and 220?15 14C yr BP (300?0 cal yr BP; UCIAMS-38252), respectively.
Like the 14C dates reported here, direct AMS dating of the Santa Rosa
fossil fox remains provided a date of 1440?50 14C yr BP (1480?
1280 cal yr BP; UCR-3563; Shelley, 2001).
AMS measured ?13C values were also obtained for the three San
Miguel Island fox specimens, with the preliminary values ranging
Table 1
AMS 14C dates on paleontological island fox bones
Locality/provenience Museum catalog numbera AMS lab num
San Miguel Island Locality V-7c SBMNH-127 UCIAMS-401
San Miguel Island Locality V-10c SBMNH-397 UCIAMS- 38
San Miguel Island Locality V-11 SBMNH-138 UCIAMS- 38
Santa Rosa Island Upper Tecolote Membere SBMNH-2327 UCR-3563
a SBMNH? Santa Barbara Museum of Natural History.
b UCIAMS? University of California-Irvine Accelerator Mass Spectrometry Facility; UC
c The chemical fraction dated is the XAD-puri?ed hydrolyzed gelatin hydrolyzate of K
roughly 2?.
d All dates were calibrated using CALIB 5.0.2 (Stuiver and Reimer, 1993; Stuiver et al., 2
Because UCIAMS-40173 was enriched in marine carbonwe calibrated this sample as
makes it roughly 600 yr older with a 2 sigma range of 7160?6910 cal yr BP.
e Date obtained from Shelley (2001:30).1993:181).
These preliminary data suggest that at least some island foxes were
consuming large amounts of marine foods. It is possible that foxes
were scavenging marine carrion on beaches, as modern foxes are
known to do (Moore and Collins, 1995), scavenged marine foods
around Native American villages, or were fed marine foods by Native
Americans. Given the high marine signature for the 6400 yr old fox,
the two latter possibilities seem probable, especially if foxes were
semi-domesticates or pets. Because of the relatively small size of our
preliminary sample, however, more stable isotope studies of fox bones
are needed to assess their ancient diet.
Discussion
Prior to our study, several researchers speculated that island foxes
evolved from gray foxes that arrived on the northern islands by
chance-rafting during the Pleistocene, with Native Americans later
transporting island foxes to the southern islands (Wenner and
Johnson, 1980; Collins, 1991a; Vellanoweth, 1998). Others speculated
on human-assisted dispersal of foxes to all the islands (Vellanoweth,
1998; Kennett, 2005:49). Through analysis of island fox and main-
land gray fox skeletons, Collins (1991a, 1993) suggested that gray
foxes may have ?rst colonized the islands just prior to the Wisconsin
glaciation (?25,000 14C yr BP), and under selective pressure and
inbreeding rapidly dwarfed into the small-sized island fox in
10,000 yr or less. This proposition was supported by morphometric
and genetic data interpreted in light of the ?fossil? Santa Rosa Island
fox specimen now known to be of late Holocene age (see Collins,
1991a, 1993; Wayne et al., 1991; Goldstein et al., 1999; Aguilar et al.,
2004). These dates were also based on the timing of the breakup of
Pleistocene Santarosae with foxes thought to have arrived while the
northern islands were still connected and closer to the mainland, an
event now thought to have occurred between about 10,000 and
9000 cal yr BP, some 4000 to 3000 yr after human colonization (see
Porcasi et al., 1999; Kennett et al., 2008). Because the genetic and
rb Material dated ?13C ? VPDB Conventional radiocarbon
age, 14C yr BP?1 SD
cal yr BP age range
(2 sigma)d
Bone collagenc ?11.6 6120?25 6400?6210
Bone collagenc ?18.4 990?15 950?800
Bone collagenc ?19.5 220?15 300?0
Bone collagen n/a 1440?50 1480?1280
University of California-Riverside Radiocarbon Laboratory.
-Collagen (see Waters and Stafford, 2007). AMS measured ?13C values have an error of
). UCIAMS-38253, UCIAMS-38252, and UCR-3563 were calibrated as terrestrial samples.
rine sample applying a ?R of 225?35. Calibrating UCIAMS-40173 as a terrestrial sample
of eggshells at some fossil localities, Guthrie (1993:410, 1998, 2005)
argued that ground-nesting colonies of Chendytes existed on SanMiguel
Island in the late Pleistocene. Chendytes bones have also been identi?ed
in island archaeological sites as recent as the middle to late Holocene
(Jones et al., 2008). Many of these later bones may be from birds that
bred on offshore rocks, but the late Pleistocene specimens are from
mainlandportionsof SanMiguelwhere, if present, foxeswouldhavehad
ready access to Chendytes nests, eggs, and ?edglings. Because foxes prey
on ground nesting bird eggs and chicks, if foxes had arrived prior to
human arrival such breeding colonies seem unlikely. A modern analog
may be the recent expansion of ground breeding northern harriers
(Circus cyaneus), western gulls (Larus occidentalis), and Brandt's
cormorants (Phalacrocorax penicillatus) on San Miguel Island after all
foxeswere incarcerated during captive breeding efforts beginning in the
late 1990s (Coonan et al., 2002, 2005; Charles Drost, personal
communication, 2008). The expansion of these birds to conspicuous
SCRI-131 Late Holocene 2 2 Collins (1991a)
SCRI-147 Late Holocene N18 5 Collins (1991a)
SCRI-206 n/a 1 1 Collins (1991a)
SCRI-236 (aka SCRI-83) Late Holocene 7 6 Collins (1991a)
SCRI-240 Historic 5 n/a Noah (2005)
SCRI-306 670?410 n/a n/a Arnold (1987)
SCRI-328/330 Historic 9 n/a Noah (2005)
SCRI-333 (aka SCRI-3) 6170?1260 N45 13 Collins (1991a)
SCRI-474 (aka SCRI-100) Late Holocene N46 11 Collins (1991a)
SNI-7 n/a n/a 20 Collins (1991a,b)
SNI-11 5890?5660; 3840?510 N5 2 Collins (1991a)
SNI-25 740?Historic n/a 10 ?
SNI-39 3210?2780 11 5 Shelley (2001)
SNI-51 2840?1840 2 1 Collins (1991a)
SNI-102 2780?2150 n/a n/a Martz (2005)
SNI-119 n/a 4 1 Collins (1991a)
SNI-160 1710?930 n/a n/a Martz (2005)
SNI-161 5440?5270 1 1 Vellanoweth (1998)
SCAI-17 5920?3900; 1330?880 3 2 Collins (1991a)
SCAI-45 1450?1050 3 1 Collins (1991a)
SCAI-137 270?230 3 1 Collins (1991a)
SCLI-43 10,210?520 N28 4 Collins (1991a)
SCLI-48 n/a 1 1 Collins (1991a)
SCLI-1215 5300?460 N2 2 Collins (1991a)
SCLI-1524 2910?460 N20 9 Collins (1991a)
Paleontological specimens
SRI-Tecolote member 1480?1280 3 1 Collins (1991a);
Shelley (2001)
SMI-Locality 7c 6400?6210 1 1 Guthrie (1993)
SMI-Locality 10 950?800 6 1 Guthrie (1993)
SMI-Locality 11 300?0 1 1 Guthrie (1993)
a SMI = SanMiguel, SRI = Santa Rosa, SCRI = Santa Cruz, SCAI = Santa Catalina, SNI = San
Nicolas, SCLI = San Clemente. NISP (Number of Identi?ed Specimens) and MNI
(Minimum Number of Individuals) based on Collins (1991a,b) unless otherwise noted.
For additional details see Collins (1991a), Shelley (2001), and sources cited therein. Fox
bones fromunknown sites or localitieswere excluded. An additional NISP of 30 fox bones
presented in Colten (2001) could be from SCRI-191, ?192, ?240, ?330, and/or ?474.
96 T.C. Rick et al. / Quaternary Research 71 (2009) 93?98morphologic data do not provide absolute ages, the fossil and
archaeological records supply the most direct means of documenting
the chronology of island fox dispersal.
Numerous paleontological projects have been conducted on the
Channel Islands, including research in paleontological and archae-
ological deposits at Daisy Cave (CA-SMI-261) on San Miguel
(Guthrie, 1980; Walker, 1980; Erlandson et al., 1996), late Pleisto-
cene and Holocene deposits at Arlington Springs (CA-SRI-173) on
Santa Rosa (Johnson et al., 2002), late Pleistocene localities on San
Miguel and Santa Rosa (Guthrie, 1993, 1998, 2005), late Pleistocene
deposits on Anacapa (Lipps, 1964), and several mammoth localities
on Santa Rosa, San Miguel, and Santa Cruz (Orr, 1968; Cushing et al.,
1984; Gray and Harz, 1998; Agenbroad 1998, 2002b; Thaler, 1998;
Agenbroad et al., 2005). These projects have yielded faunal
assemblages that include abundant avian materials, extant and
extinct micro-mammals, reptiles and amphibians, and mammoths
(Guthrie, 1980, 1993; Walker, 1980; Agenbroad, 1998). Orr (1968)
estimated that a minimum of 200 mammoths had been identi?ed
by the early 1960s. Agenbroad's (1998, 2002b) surveys on Santa
Rosa, San Miguel, and Santa Cruz identi?ed over 140 new mammoth
localities.
In contrast, island foxes are rare or absent in fossil deposits and
the few that have been found are all Holocene in age. Moreover, at
Daisy Cave, pre-human deposits lack island foxes, yet post-human
archaeological deposits contain them (Walker, 1980). If island foxes
originated from a small founding population prior to human arrival,
?nding the remains of those presumably full-sized foxes in the
fossil or archaeological records would be dif?cult. However, the
complete absence of island foxes in pre-human age deposits is
peculiar, especially given the large samples of birds, micro-
mammals, and mammoths that have been recovered in Quaternary
deposits.
Island fox remains occur in at least 40 island archaeological sites,
but many of these are from fairly poorly dated multi-component sites
(Table 2). A few of the foxes identi?ed in island sites (e.g., SRI-1, SRI-3,
SMI-261, and SCLI-43c) could conceivably predate the ca. 6400 cal yr
BP date reported here. Recent excavation of several sites dated
between 11,000 and 8000 cal yr BP on San Miguel, Santa Rosa, and
Santa Cruz islands has produced fewmammal bones and no foxes (see
Erlandson et al., 2007), however, suggesting that foxes may have
arrived on the islands sometime after about 10,000?9000 cal yr BP.
The ca. 6400?6200 cal yr BP fox dates reported here are about the
same age as the earliest securely dated Channel Island dog remains
(Rick et al., 2008).
Recent studies from elsewhere around the world lend support to a
human-assisted dispersal of foxes to all the Channel Islands. For
example, White (2004) described the translocation of the northern
common cuscus (Phalanger orientalis) to New Ireland by hunter-
gatherers as early as 20,000 yr ago. Ancient human translocation of
animals has also been documented on islands in the Caribbean, North
Atlantic, Mediterranean, and Paci?c (Grayson, 2001). Researchers
have also suggested that most of the extant mammalian fauna on the
Channel Islands and some reptiles were intentionally or unintention-
ally introduced by Native Americans, including skunks, harvest mice,
deer mice, shrews, ground squirrels, rattlesnakes, dogs, and foxes
(Walker, 1980; Wenner and Johnson, 1980; Johnson, 1983; Collins and
George,1990; Guthrie,1998; Rick et al., 2008).When the late Holocene
Santa Rosa fox specimenwas still thought to be late Pleistocene in age,
Wenner and Johnson (1980:515?516) argued that foxes likely rafted
out accidentally to the northern islands during storms, but they noted
that ?it is also conceivable that the early aborigines initially brought
the ?rst fox to one or another of the superislands,? a proposition now
supported by the fossil and archaeological records.
Additional support for the antiquity of foxes on the Channel Islands
may come from the extinction of Chendytes lawi (?ightless scoter) and
Fratercula dowi (a burrowing nesting alcid). Based on the abundanceTable 2
Archaeological and paleontological island fox remains from the Channel Islandsa
Site or locality Age (cal yr BP) NISP MNI References
Archaeological specimens
SMI-1 7140?3250 2 1 Collins (1991a)
SMI-87 4790?2340 1 1 ?
SMI-261 11,600?640 13 1 Collins (1991a)
SMI-470 460?Historic 1 1 ?
SMI-481 1410?920 n/a 1 ?
SMI-525 3230?520 1 1 Collins (1991a)
SMI-603 4570?4260 1 1 ?
SRI-1 9260?2110 9 6 Collins (1991a)
SRI-2 2030?Historic N16 9 Collins (1991a,b)
SRI-3 8300?2360 3 2 Collins (1991a)
SRI-4 7410?2130 1 1 Collins (1991a)
SRI-25 n/a 2 1 Shelley (2001)
SRI-41 5470?3630 2 1 Collins (1991a)
SRI-365 n/a n/a 1 ?
SCRI-122 Late Holocene 2 2 Collins (1991a)breeding areas across the island is correlated with the fox removal.
97T.C. Rick et al. / Quaternary Research 71 (2009) 93?98If humans introduced foxes to all the Channel Islands, questions
remain about the length of time necessary for dwar?ng. Recent
syntheses suggest that morphological evolutionary rates of change are
signi?cantly faster on islands than mainland regions, especially after
initial colonization when the animals are undergoing signi?cant
selective pressure (Millien, 2006). Small colonizing populations can
also result in inbreeding, which can accelerate the dwar?ng process
(Collins, 1993). Several studies demonstrate rapid dwar?ng on islands,
including red deer on Jersey Island in 6000 yr or less (Lister, 1989,
1995) and sloths (Bradypus) on Panamanian islands between about
8900 and 3400 yr (Anderson and Handley, 2002). Analysis of a small
number of subfossil Urocyon sp. bones from Cozumel Island, Mexico
suggested that dwar?ng occurred between about 13,000 to 5000 yr
(Gompper et al., 2006). Pergams and Ashley (1999) noted signi?cant
size reduction in island deer mice populations from three California
Channel Islands in just 90 yr, however, a time frame that is far more
rapid than anything in the fossil record and one not associated with a
recent introduction or founder effect. Studies of island lizards also
provide evidence of extremely rapid change with signi?cant body size
increases in just 100 yr (Case and Schwaner, 1993). Using a
conservative estimate of 6000?5000 yr for dwar?ng, the oldest secure
ages for Channel Island foxes (?7000?6000 cal yr BP) ?ts with the
oldest known dates for humans (?13,000 cal yr BP; Johnson et al.,
2002). This assumes that we have the oldest dates for both humans
and foxes, and that we have fairly rapid evolution, issues that need to
be tested further.
Conclusions
Foxes and domestic dogs were present on California's Channel
Islands since at least the middle Holocene, and their introduction by
humans would have signi?cantly altered island ecosystems. The
purportedly pre-human-age island fox bones have now been directly
14C dated to the Holocene, with island foxes on the northern islands
for at least 6400 yr and on the southern islands (San Nicolas) for at
least 6000?5000 yr (Vellanoweth, 1998; Shelley, 2001). Several lines
of evidence support the hypothesis that Native Americans introduced
foxes to all the islands where they are currently found, including: 1)
the widespread occurrence of foxes in island archaeological sites and
absence in pre-Holocene fossil/subfossil deposits; 2) deliberate
translocation of foxes between islands by Native Americans; 3)
signi?cance of foxes in Native American religion and ceremony; 4)
presence of late Pleistocene ground nesting colonies of Chendytes and
Fratercula; and 5) rapid dwar?ng of animals on other islands around
the world. This is one of the few known animal translocations by
hunter-gatherers (see Grayson, 2001) and demonstrates a signi?cant
Native American in?uence on the structure and functioning of
Channel Island ecosystems.
A natural dispersal of foxes cannot be ruled out until additional
paleontological and genetic (especially aDNA [ancient DNA])
research is conducted, however, with the aDNA research offering a
chance to document and analyze the ancient genetic diversity of
foxes, to investigate their relationship to modern fox populations,
and to identify possible founder populations. These aDNA studies
would also be an important complement to genetic studies of
contemporary island foxes that document a small founding popula-
tion (Wayne et al., 1991; Goldstein et al., 1999; Aguilar et al., 2004).
Continued direct 14C dating of island fox bones from Channel Island
archaeological sites and interdisciplinary collaboration between
researchers will also help elucidate the antiquity, evolution, and
biogeography of the island fox, and the role of Native Americans in
island ecology. Regardless of whether foxes were transported to the
islands by humans during the Holocene or dispersed to the islands
during the late Pleistocene prior to human arrival, they are unique
animals that helped shape island ecosystems and cultures for at least
6500 yr.Acknowledgments
This project was supported by the University of Oregon, the US
Navy, and SouthernMethodist University. We thank Ann Huston, Kelly
Minas, and Steve Schwartz for supporting our research, and Curtis
Marean, Donald Johnson, and Gary Roemer for comments that greatly
improved this manuscript.
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