Microtene Fauna from Lime Hills Cave, SW Alaska

1
Microtene Fauna from Lime Hills Cave, SW Alaska
Neal Endacott and Robert E. Ackerman/Washington
State University
Figure 1. Location of Lime Hills Cave.
INTRODUCTION Lime Hills Cave is located in the Ku
skokwim drainage near Lime Village, Alaska
(Figure 1). Excavations in 1993 and 1995 (Figure
2), produced about 55 artifacts most of which are
associated with an early Holocene Denali
occupation dating between about 10,500 and 8,000
14C B.P. Abundant well-preserved faunal remains
were found in all strata (Ackerman 1993, 1996
Ruter 1999). Skeletal elements from medium and
large mammals were recovered and the oldest
deposits yielded mammoth (Mammuths sp.), horse
(Equus sp.), and bison (Bison sp.). The largest
portion of the assemblage, however, is comprised
of microtene fauna. Microtene species are members
of the rodent subfamily microtinae and include
voles, lemmings and their close relatives (Hall
1981). Small mammals can be more useful than lar
ger species as paleoenvironmental indicators due
to their greater ecological sensitivity (Guthrie
1968 Repenning et al. 1964). This assemblage
provides rare data for addressing research
questions relevant to our understanding of past
environments of interior southwest Alaska, such
as the timing of expansion of shrub birch and
boreal forests.
METHODS Microtene mandible and maxilla remains wi
th intact check teeth were identified using
comparative specimens from the Conner Zoology
Museum, Washington State University. Additional
reference sources included Bee and Hall (1956),
Gilbert (1993), Semken and Wallace (2002), Smith
(1979), and Zweiful (1994). Postcranial elements
of microtene species are identifiable only to
genus, however, their molars are morphologically
distinct and can be used for accurate
identification to the species level.
Descriptions of contemporary habitat preferences
of identified species were used to infer past
environmental settings based on changes in
relative species abundances per stratum.
Descriptions of habitat preferences, and current
ranges for recovered species, were drawn from Bee
and Hall (1956), Manville and Young (1965), and
Smith (1979).
RESULTS Seven hundred and thirty mandibular or ma
xillary specimens were identified to one of eight
species. Identifiable elements were most numerous
in stratum 3 which yielded 37 of the total
number of identifiable specimens (NISP). Stratum
1, with its high organic content, produced only
0.96 of the total site NISP, the lowest of any
depositional unit (Table 3.). Lemmus
trimucronatus is the most abundant species
producing a total NISP of 270. Synaptomys
borealis is the least abundant with a NISP of
two. The relative percentages between Lemmus tri
mucronatus and Dicrostonyx groenlandicus are
nearly equal in stratum 5, but in strata 4
through 3 Lemmus trimucronatus is nearly twice as
numerous, and in stratum 2 it is greater by a
ratio of 11.68/1. Microtus xanthognathus
increases greatly from strata 5 through 2 and is
the most abundant species in stratum 2. Microtus
pennsylvanicus abundances are consistently low
throughout the caves depositional history but
increase in later strata. Microtus miurus
exhibits its highest relative percentage (13.5)
in stratum 4. Clethrionomys rutilus increases
from stratum 3 through 1. Microtus oeconomus
remains are rare in the assemblage but show their
greatest relative abundance in stratum 1 at
14.3. However, only seven identifiable microtene
remains were recovered from this uppermost
depositional unit. Synaptomys borealis was
recovered only from stratum 2.
Table 3. Numbers of Identified Specimens Per
Stratum.
   
Figure 2. Lime Hills Cave Excavations in
Progress
Figure 4. Relative Percentages of Identified
Species Per Stratum.
Conclusions The decrease in Dicrostonyx groenland
icus, and consistently high relative abundances
of Lemmus trimucronatus from stratum 5 through 2,
indicate reduction of xeric, treeless habitats.
Greater relative percentages of Clethrionomys
rutilus, beginning in stratum 3, may correlate
with the timing of increased shrub birch in the
region. The presence of Microtus xanthognathus a
nd Synaptomys borealis in the upper strata is
associated with the expansion of boreal forests
into southwest Alaska.
Table 2. Habitat Preferences for
Identified Species.
Figure 3. Cave Stratigraphy (modified
from Ruter 1999).
Stratum 3 6.21 Sand 6.13 Coarse Silt 27.59
Fine Silt
60.07 Clay
Stratum 4 12.7 Sand 16.3 Coarse Silt 40.6
Fine Silt
30.4 Clay
Stratum 2 13.9 Sand 10.5 Coarse Silt 39.7
Fine Silt
35.9 Clay
Table 1. Radiocarbon Dates from Lime
Hills Cave.
   
Stratum 5 26.5 Sand 13.1 Coarse Silt 30.3
Fine Silt
30.1 Clay
DATING AND STRATIGRAPHY Twenty-eight 14C samples
produced uncalibrated dates from 38,500860 to
22070 B.P. (Table 1). The recent carbon may have
come from a hearth that burned between 1520 and
1660 A.D. (Ruter 199916). The AMS dates on bone
are more consistent with the inferred
depositional chronology of the caves five strata
(Table 1 Figure 2). The 14C dates cluster into
three sets at about 38,500-32,500 B.P.,
15,500-12,500 B.P. and 10,500-8,000 B.P. The
first set is part of the Boutellier interstade,
the late part of oxygen isotope stage 3 (Van
Andel 1998). These earliest dates were recovered
only from stratum 5. The second cluster overlaps
with the Birch phase of the terminal Wisconsin
(Hopkins 198210-11 Hu et al. 1995 Short et al.
1992). These dates are associated with both
strata 4 and 5. The third group corresponds to
the Pre-Boreal and Boreal periods of the early
Holocene (Iversen 1973) and are associated mostly
with stratum 3, which yielded 44 of the sites 55
artifacts. Gaps in the radiocarbon chronology oc
cur from approximately 28,000-16,000 B.P. and
8,000-4,000 B.P. Whether these gaps reflect
actual depositional hiatuses remains to be
determined.  
REFERENCES CITED Ackerman, R. E. 1993 Investig
ation of Cave 1, Lime Hills Region, Southwestern
Alaska. Report to the Alaska State Office of
History and Archaeology, Division of Parks a
nd Outdoor Recreation and Division of Geological
and Geophysical Surveys.   1996 Lime Hills Cave
1. In American Beginnings, edited by F. H. West,
pp. 470-478. University of Chicago Press,
Chicago. Bee, J. W. and E. R. Hall 1956 Mam
mals of Northern Alaska. University of Kansas
Museum of Natural History, Lawrence.
Georgina, D. 2001 The Small Mammals of Lime
Hills Cave I, Alaska. In People and Wildlife in
Northern North America, edited by S. G. Gerlach
and M. S. Murray, pp. 23-31. BAR Internation
al Series 944. Gilbert, M. B. 1993 M
ammalian Osteology. Missouri Archaeological
Society, Columbia. Guthrie, R. D. 1968 P
aleoecology of a Late Pleistocene Small Mammal
Community from Interior Alaska. Arctic
21223-224. Hall, E. R. 1981 The Mammals
of North America. John Wiley and Sons, New York.
  Hopkins, D. M., J. V. Mathews, Jr., C. E. Sch
weger, and S. B. Young 1982 Paleoecology of Be
ringia. Academic Press, New York.
Hu, F. S., L. B. Brubaker and P. M. Anderson
1995 Postglacial Vegetation and Climate Change
in the Northern Bristol Bay Region, Southwestern
Alaska. Quaternary Research 43382-392.
Iversen, J. I. 1973 The Development of
Denmarks Nature since the Last Glacial.
Geological Survey of Denmark V. Series. No 7-C.
Geology of Denmark III.
ACKNOWLEDGMENTS We wish to the thank the staff of
the Conner Zoological Museum at Washington State
University for loaning us comparative specimens
to aid in our species identifications. We also
owe debts of gratitude to Karen Lupo for access
to the zooarchaeology laboratory in the
Department of Anthropology at Washington State
University, and all the students and faculty in
our department who offered help and advice in the
preparation of this poster. Anthony Ruters
(1999) work on the site stratigraphy and pollen
sequence has been invaluable in our understanding
of the caves depositional history. Diana
Georgina (2001) did the preliminary
identifications on a portion of the microtene
data presented here.
Manville, R. H. and S. P. Young
1965 Distribution of Alaskan Mammals. U. S.
Government Printing Office. Washington, D. C.
Repenning, C. A., D. M. Hopkins and M. Rubin
1964 Tundra Rodents in a Late Pleistocene Fauna
from the Tofty Placer District Central Alaska.
Arctic 17177-197. Ruter, A. H. 1999 The
Spores, Pollen, and Sediments of the Lime Hills
Cave 1, A Paleoarctic Occupation in Southwestern
Alaska. M. A. Thesis, Department of Anthropo
logy, Washington State University, Pullman, WA.
  Semken, H. A. and S. C. Wallace 2002 Key to
Arviocline (Microtene rodents) and
Ariviocline-like Lower First Molars Recovered
from Late Wisconsin and Holocene Archaeologi
cal and Paleontological Sites in Eastern North
America. Journal of Archaeological Science
2923-32.   Short, S. K., S. A. Elias, C. F. Way
thomas, and N. E. Williams 1992 Fossil Pollen
and Insect Evidence for Postglacial Environmental
Conditions, Nushagak and Holitina Lowland
Regions, Southwest Alaska. Arctic 45381-39
2.   Smith, G. S. 1979 Mammalian Zooarchaeol
ogy, Alaska A Manual for Identifying and
Analyzing Mammal Bones from Archaeological Sites
in Alaska. Anthropology and Historic Preserv
ation Cooperative Park Studies Unit, University
of Alaska, Fairbanks.   Van Andel, T. 1998
Middle and Upper Paleolithic Environments and
the Calibration of 14C Dates Beyond 10,000 B.P.
Antiquity 7226-33.   Zweiful, M. K. 1994 G
uide to Identification of the Molariform Teeth of
Rodents and Lagomorphs of the Columbia Basin. M.
A. Thesis, Department of Anthropology, Washi
ngton State University, Pullman, WA.