PLEISTOCENE MAMMALS IN THE GREATER
YELLOWSTONE ECOSYSTEM
Christopher L. Hill
Department of Anthropology and Environmental Studies Program, Boise State University, Boise, Idaho;
[e-mail]
and, more rarely, carnivores such as scimitar
Introduction
cat, cheetah, and dire wolf. The Greater Yel-
lowstone Ecosystem consists of parts of south-
The Pleistocene, which generally corresponds
western Montana, northwestern Wyoming, and
to the Ice Age, is characterized by fluctuating
southeastern Idaho (fig. 1). The drainages of
climates that started around 3-2 million years
streams that are part of the Upper Missouri
ago and ended about 10,000 years ago, after a
River basin (such as Red Rock River, Beaver-
short, cold interval called the Younger Dryas.
head River, Jefferson River, Ruby River, and
The Pleistocene is especially important in the
Madison River) are part of this landscape in
application of ecological principles because it
southwestern Montana (fig. 2). The broad char-
is associated with the evolution and extinction
acter of the Rancholabrean communities in this
of a variety of mammals (Barnosky et al. 2004;
region is known from isolated discoveries in
Barnosky, 2005). In North America, the last
fluvial gravels and sands (chiefly of mam-
part of the Pleistocene coincides with climate
moth), fossils collected from caves, and more
change, glacial advance and retreat, and the
detailed studies of late Pleistocene stratigraphic
Rancholabrean land mammal age. The end of
sequences. Besides fossil vertebrates, some
the Pleistocene also coincides with the earliest
localities contain evidence, based on the pres-
presence of humans in North America.
ence of artifacts, for prehistoric human groups
in the region by 11,000-10,500 radiocarbon
Southwestern Montana, which includes the
(14C) years ago.
northwest part of the Greater Yellowstone Eco-
system and adjacent areas, contains evidence
The landscape of southwestern Montana is to a
for extinct Pleistocene mammals. These include
great degree the product of tectonic events and
herbivores such as mammoth, camel, and horse,
climatic change during the late Pliocene and
Pleistocene (roughly the last 3 million years).
Tectonic processes in the form of regional
faulting have led to the formation of the basin-
and-range physiographic character of the re-
gion. Volcanism centered on the area of the
Yellowstone Plateau over about the last 2 mil-
lion years is connected to regional tectonic
events extending over the last 15 million years
or so on the Snake River Plain. Volcanism in
the Pacific Range resulted in the deposition of
several tephra (volcanic ash) deposits which
serve as useful regional stratigraphic markers.
Climatic fluctuations have also played an im-
portant role, both in forming the present-day
landscape and influencing the Pleistocene pa-
leobiotic communities of the region. Late Plio-
Figure 1. Location of Jefferson, Madison, and Gallatin
Rivers in southwestern Montana in relation to Yellow- cene or early Pleistocene through Holocene
stone National Park.
glacial episodes have been documented. Most
Northwest Geology, v. 36, 2007 p. 151-166 151 The Journal of the Tobacco Root Geological Society
clude Mammuthus (cf. M.
columbi), Homotherium
serum (scimitar cat), canids
(wolf and coyote), Equus
(horse), Bison (bison), and
Camelops (camel). Else-
where in the Jefferson drain-
age, in the vicinity of Black-
tail Deer Creek, Equus,
Camelops, Bison, Ovis
(sheep), and Canis dirus
(dire wolf) have been recov-
ered from Sheep Canyon-
Orr Cave, while Mammut-
hus and Equus fossils have
been recovered within the
Ruby River drainage, and
Acinonyx trumani (cheetah),
Equus, Camelops and Ovis
canadensis (mountain
sheep) are known from the
Sheep Rock Spring locality
west of the Boulder River.
Plio-Pleistocene Geologic
Background
Climate change and tectonic
activity during the late Plio-
cene and Pleistocene have
affected the physical and
Figure 2. Location of major Pleistocene localities in south-
western Montana. biotic environments of the region. A series of
volcanic explosions occurred in the area cen-
of the mountain ranges contain evidence for tered on Yellowstone National Park. The three
multiple glaciations during the late Cenozoic, major explosions date to about 2.0, 1.3 and 0.6
while alluvial fans and terraces within the val- million years ago (cf. Hamilton, 1965; Walsh,
leys reflect the interplay between fluctuating 1971; Christiansen and Blank, 1972; Witkind,
climatic regimes and tectonic processes. 1976; Weinheimer, 1979; Mannick, 1980;
Christiansen, 1982; Sonderegger et al., 1982;
Although Pleistocene fossils have been col- Pritchett, 1993; Gansecki et al., 1998; O Neill
lected from the area for over a hundred years, and Christiansen, 2004). These events resulted
extensively studied stratigraphic sequences in the emplacement of igneous rocks. The prod-
containing Pleistocene vertebrate remains are ucts of this local volcanic activity and volcanic
relatively uncommon in southwestern Montana. ash beds originating from the Cascade region
Early collections include Mammuthus serve as useful local stratigraphic markers. For
(mammoth) fossils found in the drainage of the example, the late Pleistocene Glacier Peak ash
14
Ruby River obtained as part of the Hayden Sur- dated to about 11,200 C years B.P. and the
vey in 1871. A significant Pleistocene locality early-middle Holocene tephras Mount Mazama
is in Centennial Valley, east of Lima, Montana, ash dated to about 6,900 14C years B.P. are visi-
along the Red Rock River. Mammal fossils in- ble in road cuts or natural exposures, and have
152
also been documented in stratigraphic cores. provided a variety of contexts that can be re-
Both the Glacier Peak and Mazama volcanic lated to paleobiotic patterns in southwestern
ashes are present in a stratigraphic core col- Montana. Pleistocene mammal fossils have
lected from Kearns Basin, within the Beaver- been recovered in the vicinity of the Red Rock
head drainage in the southern Pioneer Moun- River (the Merrell Locality), Blacktail Creek
tains (Foit et al., 1993). The Glacier Peak and (Sheep Canyon Cave), South Everson Creek,
Mazama tephras are exposed along the Jeffer- Alder Gulch, Dry Boulder Creek, Sheep Rock
son, Madison, and Gallatin Valleys (cf. Mon- Spring, and Point-of-Rocks Cave (fig. 2). These
tagne, 1965:51; Kellogg, 1992) and have also localities contain a record of biodiversity that
been documented in the Yellowstone Plateau can be related to changes in physical land-
area (cf. Whitlock, 1993), and elsewhere in the scapes and biotic habitats associated with re-
upper Missouri basin (Lemke et al., 1975; gional Quaternary tectonic and climate events.
Davis and Greiser, 1992).
The most extensively studied Pleistocene pale-
The mountains within southwestern Montana ontological locality in the Greater Yellowstone
supported glaciers at various times during the Ecosytem is near Red Rock River, a major
Pleistocene (Alden, 1953; Hall and McMannis, stream in the southern area of the Jefferson
1960; Paul and Lyons, 1960; Hall, 1961; Sloan, River drainage (fig. 3). The locality is east of
1960; Montagne, 1960; Reshkin, 1963; Rich- Lima, which is about 45 miles south of Dillon.
mond, 1965; Hadley, 1969; Jacobs, 1969; Mon- Red Rock River flows from east to west
tagne, 1972; Pierce, 1979; Gary, 1980; Roy and through the Centennial Valley, surrounded to
Hall, 1981; Hall and Heiny, 1983; Richmond, the north by the Snowcrest and Gravelly
1986a, 1986b; Locke, 1989; Hall, 1990; Locke Ranges and to the south by the Centennial
1990; Schneider, 1990a, 1990b; Locke and Mountains. Four classes of animals have been
Schneider, 1990; Lundstrom, 1990; Pritchett, recovered: Osteichthyes (bony fish), Aves
1990; Ritter et al., 1990; Pritchett, 1993; Ritter (waterfowl), Amphibia (amphibians), and
et al., 1993; Sturchio et al., 1994; Bartholomew Mammalia (Dundas 1990, 1992; Dundas et al.,
et al., 1999). Moraines within many of the 1996; Hill, 1999; Hill and Davis, 2005; Hill
tributary valleys show the extent of past glaci- 2006a, 2006b). Table 1 provides a list of the
ations. Alluvial fans and terraces on the flanks mammals recovered from Centennial Valley,
of the mountains and in the valleys are com- while table 2 is a list of radiocarbon dates. Fi-
posed of sediments of glaciofluvial origin, de- nite radiocarbon ages range from about 49,350
14
posited as outwash from glacial meltwater. Late C years B.P. (Beta-116519) to about 19,310
14
Cenozoic lacustrine, paludal, and spring (e.g. C years B.P. (Beta-77826). Several measure-
tufas) sediments are present in the valleys, as ments indicate some remains are older than
14
are aeolian silts (loess) and sands. Vertebrate 52,800 C years B.P. The faunal assemblages
remains have been recovered from some of are from several sedimentary units and appear
these depositional contexts and have also been to have been affected by a variety of ta-
found in caves and rock shelters. Stratigraphic phonomic processes reflecting the dynamics of
and geomorphic relationships of these various pre-burial deposition, burial, and post-burial
deposits can be linked to both paleoclimatic events.
chronologies and tectonic events. This geochro-
nologic-paleoenvironmental framework serves Stratigraphic contexts and sedimentologic fa-
as a basis for evaluating the late Pliocene and cies associated with the Centennial Valley
Pleistocene paleobiotic communities of the re- mammal fossils reflect a variety of depositional
gion. and post-depositional processes. These contexts
provide information on the factors leading to
the accumulation of the fossils. Five strata have
Pleistocene Mammal Localities
been designated (figs. 4-7). The oldest set of
deposits is stratum A which contains alluvial,
The climate and physical environmental
lacustrine, and possibly colluvial sediments.
changes that occurred during the Quaternary
153
Table 1. Mammal species from Centennial Valley, southwestern Montana.
TAXON STRATUM
Carnivora
Canis latrans (coyote) Stratum C
Canis lupus (gray or timber wolf) Unknown context
Ursus sp. indet. (bear) Unknown context
Homotherium serum (scimitar-tooth cat) Unknown context (beach)
Rodentia
Spermophilus sp. indet. (squirrel) Unknown context
Castor canadensis (Canadian beaver) Unknown context
Lemmiscus curtatus (sagebrush vole) Stratum C
Ondatra zibethicus (muskrat) Strata A-B or B
Perissodactyla
Equus sp. indet. (horse) Stratum C, D
Artiodactyla
Camelops sp. indet. Strata C, D
Cervidea sp. indet. (deer) Stratum C
Odocoileus hemionus or O. virginianus Unknown context
(mule deer or white-tailed deer)
Antilocapridea americana (pronghorn) Unknown context
Bison sp. indet.(bison) Stratum D
Proboscidea
Mammuthus columbi (Columbian mammoth) Strata A, A-B or B, C, D
154
TABLE 2: Radiocarbon Measurements from Centennial Valley
Age Lab Number Material/Method Location Other
ES-26-7 South Area: Either
>52,800 SR-6012 Mammuthus tooth,
(Excavation E South ½, Stratum A or B
Chem-6817 XAD-gelatin, KOH-
Level 26)
collagen
ES-27-1 South Area: Stratum
>52,800 SR-6013 Mammuthus tooth,
(Excavation E South ½, B
Chem 6821 XAD-gelatin, HOH-
Level 27)
collagen
>52,800 SR-6016 Equus upper mo- Ib#12, 95.2.155 North Area: Stratum
D
Chem-6833 lar, XAD-gelatin,
KOH-collagen
Ib#21 North Area:
>52,800 SR-6017 Mammuthus tusk,
Stratum D
XAD-gelatin, KOH-
collagen
CS-21-1 North Area:
49,350 +/- Beta-116519 Mammuthus molar
LI94.5.277 Stratum A
1,500 fragments
154, MS686 -19.2 C13/C12
Not in stratigraphic context -11.1 C13/C12
43,970 +/- Beta-110647 Cygnus-Olar, bone
370 collagen
East of Test Pit E, from South Area:
>41,940 Beta-83614 Humates (HCl/
backhoe trench, South Stratum B
NaOH/HCl)
Block -28.2 C13/C12
Excavation E South Area:
36,520 +/- Beta-74032 Organic sediments
Stratum B
710 from Mammuthus
-26.0 C13/C12
rib
Dundas specimen 10027 South Area:
>33,990 Beta-36206 Mammuthus fibula,
Stratum B
bone collagen
97FS36 South Area:
32,470 +/- Beta 111325 Mamuthus (tusk,
LI96.4.44 Stratum B
270 bone collagen,
L3FS36 -25.2 C13/C12
KOH)
p. 137
Station E4 North Area: Stratum
30,400 +/- SR-6018 Camelops,
Hill specimen C
590 Chem-6839 XAD-gelatin,
KOH-collagen
Ia#4 North Area:
26,630 +/- SR-6015 Equus, XAD-
Stratum D
190 Chem-6826 decalcified colla-
gen
25,030 +/- Beta-36205 Mammuthus, meta-  Channel fill re. Dundas North Area:
specimen 10006 = debris Stratum D
510 tarsal, bone colla-
flow
gen
K#29 South Area:
23,120 +/- SR-6014 Mammuthus tusk
Excavation K Stratum B
1190 XAD-gelatin, KOH-
collagen
ML-98-CLH97-C, Stratum D, North Area:
21,530 +/- Beta-118755 Bone collagen,
fragment of bone in matrix Stratum D
100 KOH
above TL3 sand sample -20.9 C13/C12
Debris flow = Stratum D -23.7
19,290 +/- Beta-77826 Collagen, KOH
90
155
Figure 3. Location of Merrell Site in Centennial Valley.
Stratum B consists of dark, organic-rich sedi- higher frequencies of mammal fossils is along
ments deposited in a swamp or bog. Silts, the interface of strata A-B and in the lowest
sands, and gravels from stratum C mostly rep- part of stratum B (fig. 5). There are no articu-
resent alluvial deposition. Stratum D is chiefly lated specimens, but there are concentrations of
composed of a debris flow. It overlies a sandy bones, tusk and teeth of mammoth (fig. 6).
facies of stratum A. After strata A-D were de- Other faunal materials from this taphonomic
posited, they were affected by soft-sediment context include Ondatra zibethecus (muskrat)
deformation-liquefaction, and faulting, perhaps and bivalves. These may include bones that
linked to local tectonic events. The youngest accumulated on the surface of stratum A and
depositional unit, designated stratum E, con- then were buried within stratum B, as well as
sists of colluvium. There is evidence of exten- elements that accumulated during the deposi-
sive bioturbation (biologic mixing) in stratum E tion of the stratum B organic-rich sediments.
and in parts of stratum C. Radiocarbon measurements, if reliable, suggest
that this taphonomic context contains a tempo-
Vertebrate remains found within stratum A are rally mixed fossil assemblage. Fragments of
14
usually rare and isolated, except near its upper mammoth teeth were dated at >52,800 C
contact with stratum B (fig. 4). One example of years B.P. (SR-6012, SR-6013), while radiocar-
14
an isolated find within stratum A is a patella of bon ages on tusk fragments are 32,470 C
a proboscidean (probably from Mammuthus). It years B.P. (Beta-111325) and 23,120 14C years
is likely that some of the fossils found within B.P. (SR-6014). These could reflect a ta-
stratum A, especially near its upper contact phonomic or formational context associated
with stratum B, have been moved by post- with surface exposure within a small basin, and
depositional events. burial in or incorporation into a marsh.
The first taphonomic context in which there are The alluvial deposits of stratum C also contain
156
Figure 4. Stratigraphic profile in Centennial Valley showing Pleistocene strata A-C and Holocene colluvium.
Figure 5 (above). Stratigraphy at Centennial Valley verte-
brate locality. Dark layer is stratum B. It over lies stratum A
and underlies stratum C.
Figure 6 (left). Mammoth tooth in stratigraphic context.
157
vertebrate remains. These include including The depositional variability reflected in the
limb bone, tooth, and tusk fragments of mam- stratigraphic record indicates that the Centen-
moth, and fragments from Camelops (camel), nial Valley vertebrate assemblages are the re-
Equus (horse), Canis latrans (coyote), a large sult of at least three different taphonomic con-
artiodactyl, Lemmiscus curtatus (sagebrush texts. The dispersal, scattering, and accumula-
vole), Pices (fish), and Anatidae (duck). The tion of bones associated with the strata A-B
14
radiocarbon age on camel is about 30,400 C appears to have occurred in a marsh-pond ba-
sin. Transport, deposition and
burial of skeletal parts recov-
ered within stratum C was the
result of hydraulic events asso-
ciated with fluvial conditions.
The concentration of mam-
moth fossils in stratum D oc-
curs within a debris flow. Sub-
surface movements post-
depositional crushing by sedi-
ment overburden along with
liquefaction and faulting
have also affected the charac-
ter of the fossil record. Horse
remains are associated with
both fluvial and debris flow
deposits. Camel and wolf re-
Figure 7. Debris flow (stratum D) with mammal fossils in
Centennial Valley.
years B.P. (SR-6018). These fossils are distrib-
uted throughout the sequence of stratum C,
within fluvial gravels and sands interbedded
with silts. Thus, these vertebrate remains repre-
sent a taphonomic context primarily associated
with stream transport and burial.
A third sedimentological setting is associated
with the fossils from stratum D, consisting of a
fine-grained matrix with limestone and quartz-
ite cobbles and bones, interpreted as a debris
flow (fig. 7). Most of the faunal material con-
sists of remains of mammoth (tusk, teeth, and
bones, fig. 8) as well as some elements of
Equus (horse) and Bison (bison). Based on the
radiocarbon ages, this assemblage is temporally
mixed. Fragments of mammoth and horse bone
have measurements indicating ages of >52,800
(SR-6016, SR-6017) and finite ages of 26,630
14
C years B.P. (SR-6015) and 19,310 14C years
B.P. (Beta-77826). Thus, the youngest fossils
from Centennial Valley appear to date to Figure 8. Mammoth tooth within stratum
D, Centennial Valley.
around the Last Glacial Maximum.
158
mains have been identified from alluvial con-
texts, while bison were recovered only in asso- Pleistocene vertebrate remains have been re-
ciation with the debris flow. All three sedimen- covered east of Dillon from the Alder Creek
tologic contexts contain evidence of mammoth. area, within the Ruby River drainage (fig. 2).
The Ruby River flows northeastward into the
Two terraces are present along the Red Rock Beaverhead-Jefferson Valley. It is bounded to
River Valley southeast of Lima (Scholten et al., the south by the Ruby Range and to the north
1965); they have been interpreted as being con- by the Tobacco Root Mountains. F.V. Hayden
nected with Pleistocene mountain glaciation. obtained Pleistocene fossils from the vicinity of
Red Rock River flows northwest, between the Virginia City, at Alder Gulch (Hayden, 1872;
Tendoy Mountains to the southwest and the Merrill, 1999). The remains were assigned to
Blacktail Mountains to the northeast and Elephas (= Mammuthus) primigenius by Hay-
merges with Horse Prairie Creek to form the den (1872). Later some of the proboscidean
Beaverhead River at the Clark Canyon Reser- remains were identified as E. columbi (Hay,
voir, about 11 miles south of Dillon (fig. 2). 1924). Other mammoth fossils from Alder
Blacktail Deer Creek flows into the Beaverhead Gulch were recovered during placer mining
River from the east and is bounded by the prior to 1894 and are in the collection of the
Blacktail Mountains to the southwest, the Virginia City Museum and Library. Along the
Snowcrest Range in the southeast and the Ruby northern flanks of the Ruby Range, fossils of
Range to the north. Along the south side of Pleistocene horse have been collected from
Blacktail Deer Creek valley, south of Dillon, gravels at the mouth of Dry Boulder Creek, and
Pleistocene vertebrate remains were recovered from silts near Dry Georgia Creek (Petkewich,
from Sheep Canyon Cave. The locality was 1972).
excavated by P. Orr between 1925 and 1930
(Campbell, 1978). Faunal remains include A late Pleistocene vertebrate assemblage was
Equus, Camelops, Bison and Ovis. The remains collected west of the Boulder River on the
of Canis dirus (dire wolf) have been identified flanks of the southern end of Bull Mountain, at
from Orr Cave (Kurten, 1984), which is proba- the Sheep Rock Spring locality (Wilson and
bly another designation for Sheep Canyon Davis, 1994; Davis, 1997). The (Northern)
Cave. Boulder River flows southward from the Elk-
horn Mountains and joins the Jefferson River
Southwest of Dillon, studies in the Horse Prai- near Whitehall and Cardwell, about 55 miles
rie Creek and Grasshopper Creek Basins and northwest of Dillon (fig. 2). At least three ter-
along the adjacent slopes of the Beaverhead races can be recognized in the Boulder River
Mountains indicate at least six pre-Bull Lake Valley north of Cardwell. These were assigned
age glacial advances (Turner et al., 1988). Six- to the early to middle and late Pleistocene
teen terraces are recognized near South Everson ( second and third sets ) by Alden (1953:80).
Creek (fig. 2), which flows from the foothills of Five stepped pediments levels were studied by
the Beaverhead Mountains into Horse Prairie Morgan and Hall (1982). Faunal remains in-
Creek (Bonnichsen et al., 1987, 1992). The clude cheetah (Miracinonyx trumani), horse
lowest terrace contains what is probably Gla- (Equus sp.), camel (Camelops sp.), and large
14
cier Peak volcanic ash (ca. 11,200 C years mountain sheep (Ovis canadensis catclawen-
B.P.) as well as flaked mammoth bone sis). The lowest part of the sequence has radio-
14
(Bonnichsen et al., 1987). Possible fragments carbon dates slightly older than 10,000 C
of mammoth bone were associated with sedi- years B.P. (Hill, 2006a).
ments consisting of cobbles and boulders em-
bedded in clays (Bonnichsen et al., 1990; Bon- Point-of-Rocks Cave (Davis and Johnson,
nichsen et al., 1992). The clays may be late 1988) is situated on the slopes of the Tobacco
Pleistocene paludal or lacustrine deposits Root Mountains adjacent to the Jefferson River,
(Turner et al., 1987; Turner et al., 1988). south of Whitehall and east of Renova. Fossils
159
recovered from the cave include a possible ered in the region. These range in age from
14
Bl ancan age Megant eron s p. about 10,500-10,000 C years B.P. for Agate
14
(Machairodontinae) (personal comm. to D. Basin (fig. 10) as well as 10,200-8,800 C
Rasmussen from L.D. Martin, 1999) and Equus years B.P. for Alberta, Scottsbluff and Eden
(Davis, 1997). artifact forms (fig. 11) (Holliday, 2000). These
discoveries suggest that humans were present
in this region of North America during the
Evidence for Late Pleistocene Humans
Younger Dryas (from about 10,900 to 10,200
14
C years B.P.) or slightly earlier and appear to
The earliest well-documented evidence for hu-
have persisted throughout the Pleistocene-
mans in North America come from discoveries
Holocene transition.
associated with Clovis and Folsom artifacts.
These types of artifacts are considered to be
time indicators for the end of the Pleistocene Ecological Interpretations
and have been discovered with extinct Ran-
and Conclusions
cholabrean mammals. Clovis artifacts have
been found in stratigraphic contexts with mam-
Large and small mammals in the Greater Yel-
moths, while Folsom artifacts are associated
lowstone Ecosystem include both carnivores
and herbivores (Bailey, 1930;
Hadly, 1986; Streubel, 1989;
National Research Council,
2002; Cannon and Cannon,
2004). Carnivores present to-
day include Ursos arctos
(grizzly bear), Ursus ameri-
canus (black bear), Felis con-
color (mountain lion), Canis
latrans (coyote), and Canis
lupus (wolf). Herbivores in-
clude Cervus elaphus (elk or
wapiti), Odocoileus hemionus
(mule deer), Bison bison
(bison), Alces alces (moose),
Figure 9. Fragment of Folsom point found north of Red Rock River, Centen-
Ovis Canadensis (bighorn
nial Valley (from Hill and Davis, 2005).
sheep), Antilocapra americana
with extinct forms of bison. In eastern Idaho,
Folsom artifacts have also been found with
mammoth fossils (Miller and Dort, 1978).
Clovis artifacts may date to about 11,100-
14
10,800 C years B.P. (Waters and Stafford,
2007), while Folsom artifacts may range from
14
about 10,900-10,100 C years B.P. (Holliday
2000). A stratified sequence at Indian Creek on
the flank of the Elkhorn Mountains in western
Montana contains a Clovis component (Davis
and Greiser, 1992; Hill and Davis, 2005). Fol-
som artifacts have also been found regionally.
One example was found north of Lima Reser-
voir in Centennial Valley (fig. 9). Slightly
younger artifact forms dating to about the Pleis-
Figure 10. Agate Basin points from Centennial Valley
tocene-Holocene transition have been discov-
(from Hill and Davis, 2005).
160
(pronghorn), and Odocoileus virginianus cene. Herbivores show a pattern similar to the
(white-tailed deer). Some of the smaller mam- carnivores. Some, like Mammuthus
mals include Erethizon dorsatum (porcupine), (mammoth), Equus (horse), and Camelops
Lepus americanus (snowshoe hare), Castor (camel) did not survive the end of the Pleisto-
canadensis (beaver), Ondatra zibethicus cene, while other animals such as Odocoileus
(muskrat), Gulo gulo (wolverine), Mustela (mule or white-tailed deer), Ovis canadensis
(weasel), Mustela vison (mink), Martes Ameri- (bighorn/mountain sheep) and Antilocapridea
can (pine marten), Martes martes (fisher), americana (pronghorn), and Bison (bison) per-
Taxidea taxus (badger), Lutra canadensis (river sisted regionally. In contrast to the larger
otter), Ochotona princes (pika), Marmota mammals, rodents appear to have persisted
flaviventrus (yellow-bellied marmot), Tamias without major extinctions during the last glacial
minimus (least chipmunk), Spermophilus ar- to interglacial transition, although some range
matus (ground squirrel). changes may have occurred. This is illustrated
by the Merrell Locality in Centennial Valley
The Pleistocene mammals for southwest Mon- where Castor canadensis (Canadian beaver),
tana fall into the two categories: those that are Lemmiscus curtatus (sagebrush vole), and On-
extinct and those that are still present. This datra zibethicus (muskrat) are found in late
seems to suggest some ecological relationships Pleistocene sediments. In terms of patterns of
that exist today may have persisted in the re- extinctions, there appears to be a dichotomy
between some large mammals, regardless of
whether they are herbivores or carnivores, and
small mammals. The extinction of large mam-
mals near the end of the Pleistocene has been
linked to both climate change and interactions
with humans (Barnosky et al., 2004).
References Cited
Alden, W.C., 1953, Physiology and glacial geology
of western Montana and adjacent areas: United
States Geological Survey Professional Paper 231.
Bailey, V., 1930, Animal life of Yellowstone Na-
tional Park: Springfield, Illinois, Charles C. Tho-
mas.
Figure 11. Late Pleistocene and Early Holocene points
(Alberta, Scottsbluff, and Eden) from Centennial Valley
Barnosky, A.D., 2005, Effects of Quaternary cli-
(Hill and Davis, 2005).
matic change on speciation in Mammals: Journal of
Mammalian Evolution, v.12, p. 247-264.
gion since the Pleistocene. It also implies that
Barnosky, A.D., Koch, P.L., Feranec, R.S., Wing,
some aspects of the Greater Yellowstone Eco-
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...saw several bald Eagles and two large white headed fishing-
hawks boath these birds were the same common to our country.
From the number of rattle snakes about the Clifts at which we
halted we called them the rattle snake clifts. This serpent is the
same before discribed with oval spots of yellowish brown. The
river below the mountains is rapid rocky, very crooked, much
divided by islands and withal shallow. After it enters the moun-
tains its bends are not so circuetous and it's general course more
direct, but it is equally shallow les divided more rocky and
rapid.
Capt. Lewis, August 10, 1805
166