North American ursid (Mammalian: Ursidae) defaunation from Pleistocene to recent.

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NORTH AMERICAN URSID (MAMMALIA:
URSIDAE) DEFAUNATION FROM
PLEISTOCENE TO RECENT
JOAQUÍN ARROYO-CABRALES LABORATORIO DE ARQUEOZOOLOGÍA, SUBDIRECCIÓN DE LABORATORIOS Y APOYO
ACADÉMICO, INAH, MONEDA # 16, COL. CENTRO, 06060 MÉXICO, CDMX, MEXICO, ARROMATU@HOTMAIL.COM
EILEEN JOHNSON MUSEUM OF TEXAS TECH UNIVERSITY, BOX 43191, LUBBOCK, TX 79409-3191, USA, EILEEN.JOHNSON@TTU.EDU
RUSSELL W. GRAHAM EARTH AND MINERAL SCIENCES MUSEUM, THE PENNSYLVANIA STATE UNIVERSITY, STATE COLLAGE, PA
16802, USA, RGRAHAM@EMS.PSU.EDU
VÍCTOR ADRIÁN PÉREZ-CRESPO INSTITUTO DE GEOLOGÍA, UNAM, CIUDAD UNIVERSITARIA, DEL. COYOACÁN, 04510 MÉXICO,
CDMX, MEXICO,VAPC79@GMAIL.COM
Abstract
North America had a large and varied biodiversity during the Quaternary, including the carnivore family Ursidae
(Mammalia, Carnivora) that during the Pleistocene was quite varied, but by the Late Pleistocene into the Holocene,
it went into a defaunation process. At least seven species occurred in Mexico and to the north, including two sub-
families, Tremarctinae and Ursinae. The rst one had at least four species, including two within the short-faced bear
Arctodus, one in the spectacled bear Tremarctos, and another undescribed, all of which are extinct but the Andean
bear Tremarctos ornatus that presently lives in South America. Three ursine species are extant, but populations and
distribution range have diminished. The polar bear Ursus maritimus now has a high extinction risk, along with the
grizzly bear U. arctos. The black bear U. americanus, however, is increasing in some areas of its range. Extinction pat-
terns are reviewed, with examples of some human-bear interactions.
Resumen
Norteamérica tuvo una gran y variada biodiversidad durante el Cuaternario, incluyendo la familia de carnívoros
Ursidae (Mammalia, Carnivora) que durante el Pleistoceno fue más variada, pero en el Pleistoceno Tardío y el
Holoceno, atravesó un proceso de defaunación. Hubo al menos siete especies que se distribuían de México hacia
el norte, incluyendo dos subfamilias, Tremarctinae y Ursinae. La primera tuvo al menos cuatro especies, incluyendo
dos dentro del oso de cara corta Arctodus, una de osos de anteojos Tremarctos y otra aún no descrita, de las cuáles
todas se extinguieron con excepción del oso andino Tremarctos ornatus que sobrevive en Sudamérica. Las tres
especies de ursinos aún existen, pero sus poblaciones y su amplitud distribucional ha disminuido, con el oso polar
Ursus maritimus que se halla en gran riesgo de extinción, así como el oso gris U. arctos, mientras que el oso negro U.
americanus tiene poblaciones que han aumentado en algunas regiones dentro de su distribución. Los patrones de
extinción se revisan, con ejemplos de algunas interacciones humano-oso.
Samenvatting
Noord-Amerika bezat tijdens het Kwartair een grote biodiversiteit met onder meer de carnivore familie Ursidae
(Mammilia, Carnivora). In het Pleistoceen was deze familie vrij gevarieerd, maar in het Laat-Pleistoceen en
Holoceen vertoont ze een sterk afname. Er kwamen tenminste zeven soorten voor in en ten noorden van Mexico,
bestaande uit twee subfamilies, Tremarctinae and Ursinae. De eerste bestond uit minstens vier soorten, waaronder
twee in het geslacht kortsnuitbeer Arctodus, één brilbeer Tremarctos en verder een nog onbeschreven soort. Deze
zijn allen uitgestorven met uitzondering van de brilbeer Tremarctos ornatus die tegenwoordig nog in Zuid-Amerika
voorkomt. De subfamilie Ursinae kent momenteel drie soorten, maar het aantal en de verspreiding zijn sterk
afgenomen. De ijsbeer Ursus maritimus wordt het meest bedreigd, net als de Grizzly beer U. arctos; alleen de zwarte
beer U. americanus vertoont in bepaalde delen van zijn verspreidingsgebied een toename in aantal. Patronen van
uitsterven worden besproken met enkele voorbeelden van interactie tussen beren en mensen.
INTRODUCTION
One of the most outstanding contributions in the past 25
years to biological studies is the proposal of the biodiversity
concept. That concept states “…the variability among living
organisms from all sources including, inter alia, terrestrial,
marine and other aquatic ecosystems and the ecological
complexes of which they are part; this includes diversity
within species, between species and of ecosystems” (UN
Convention on Biological Diversity, 1992). Biodiversity
includes all life forms living on Earth through time, from
microbes to higher vertebrate classes. The North American
subcontinent has a high biodiversity that constitutes a unique
biogeographic realm, the Nearctic. Furthermore, some
countries, such as Mexico in North America, are named as
megadiverse because they contain within their borders at
least 70% of the world species diversity. In some cases, like
Mexico, at least 10% of described species are known from
that country (McNeely et al., 1990).
AUTHORS
JOAQUÍN ARROYO-
CABRALES
EILEEN JOHNSON
RUSSELL W. GRAHAM
VÍCTOR ADRIÁN PÉREZ-
CRESPO

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That same pattern may have occurred in the past, at least
in near geological times, such as the Pleistocene. Mexico
had a quite diverse Quaternary fauna composed of 13 orders,
44 families, and 280 species (Ferrusquía-Villafranca et al.,
2010), while North America north of Mexico had 297 spe-
cies (Kurtén & Anderson, 1980). That pattern most likely is
due to both geophysical and historical factors. Geophysical
factors include the highly diverse topography, climate, and
vegetation. Historical factors include the Great American
Biotic Interchange, Last Glacial Maximum, rst entry of
humans into the Americas, extinction-driven faunal changes,
and European human-companion fauna in the latest Holo-
cene (Kidwell, 2015).
In the past 500 years, humans have triggered a wave of ex-
tinction, threats, and local population declines that have been
compared in both rate and magnitude with the ve previous
mass extinctions of Earth’s history. Others are not convinced.
Similar to other mass extinction events, the effects of this
“sixth extinction wave” extend across taxonomic groups, but
the extinction events also are selective, with some taxonomic
groups and regions being particularly affected (Dirzo et al.,
2014). This claim adds to the anthropological models for ex-
plaining Late Pleistocene extinctions, especially the overkill
hypothesis. Here, evidence is reviewed for one such group
for the Americas, the ursids.
QUATERNARY BEAR FAUNA
The Family Ursidae (Mammalia, Carnivora) has occurred
in North America from the Late Eocene (Chadronian) to
the present, with perhaps its greatest diversity during the
Late Pleistocene. In the past, four subfamilies inhabited the
Americas, these being Amphicynodontinae, Hemicyoninae,
Tremarctinae, and Ursinae (McLellan & Reiner, 1994; Hunt,
1998). The rst two, now raised to the family level (McK-
enna & Bell, 1997), are quite diverse in the Tertiary and are
extinct now. The third one still survives in South America
and the fourth in North America. The three living ursine
bears represent only a fraction of the diversity that has been
discovered in the North American fossil record (Hunt, 1998).
Most of the fossil record is assigned to the tremarctine bears
with at least four extinct genera (Fig. 1a, Table 1).
North American species today include the black bear,
Ursus americanus, and the Grizzly or brown bear, U. arctos.
Black bears have been known in North America for the last
three million years (Kurtén & Anderson, 1980) whereas the
brown bear immigrated to North America sometime after
100 ka (Kurtén & Anderson, 1980; McLellan & Reiner,
1994). The polar bear, U. maritimus, has a circumpolar
distribution, and only recently appeared in North America
(sometime in the Late Pleistocene to early Holocene, i.e.,
most likely during the Younger Dryas Chronozone; Ander-
son, 1984; Vincent, 1989) (Fig. 1b). Some authors recognize
the polar bear as the monotypic genus Thalarctos (McKenna
& Bell, 1997).
American black bears are found throughout much of
Canada, the United States, and the northern half of Mex-
ico. Although they were extirpated from large portions of
their historic range because of habitat loss and intentional
overexploitation, their occupied range has been expanding
in recent years (Pelton et al., 1999; Williamson, 2002). The
species, nevertheless, has been extirpated from large parts
of its former range, especially in the Midwest of the United
States, and in Mexico. American black bears presently
occupy all provinces and territories of Canada, except Prince
Edward Island (where they were extirpated in 1937), 41 U.S.
states (with occasional sightings in at least three others),
and 12 states of northern Mexico, as far south as the State
of Hidalgo, to the northeast of Mexico City (Hall, 1981;
Rojas-Martínez & Juárez-Casillas, 2013). A Late Pleistocene
Family Ursidae
Subfamily Tremarctinae (extinct)
Arctodus pristinus Leidy, 1854
Arctodus simus (Cope, 1879)
Tremarctos oridanus (Gidley, 1928)
Unnamed tremarctine
Subfamily Ursinae
Ursus americanus Pallas, 1780
Ursus arctos Linnaeus, 1758
Ursus maritimus Phipps, 1774
Table 1: Taxonomy of the North American Quaternar y Bears
Tabel 1: Taxonomie van de Noord-Amerikaanse kwartaire beren
Figure 1: North American maps showing Quaternary (a) and current (b) ursid species distribution
Figuur 1: Kaarten van Noord-Amerika met verspreiding van kwartaire en recente berensoorten
ab

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record comes from Tlapacoya, State of Mexico (Álvarez,
1969), and a southernmost record was reported from Cerro
Rabón, Oaxaca (Bitterli et al., 1990). The species is endemic
to North America and never has ranged outside of these
three countries. During the past two decades, most American
black bear populations have grown both numerically and
geographically (Williamson, 2002).Fossil records in North
America are known from the Middle Pleistocene into the
Holocene (Kurtén and Anderson, 1980), and black bears are
the most common of the Pleistocene bears (Graham & Lun-
delius, 1994; McLellan & Reiner, 1994). A major body size
reduction in black bears occurs at the end of the Pleistocene
and perhaps throughout the Holocene (Graham, 1991).
The brown bear is the most widely distributed ursid
globally. Now greatly restricted from its former distribution
range, it once ranged across a large portion of North Ameri-
ca, including northern Mexico, south to central Durango (Ce-
ballos & Oliva, 2005). An archaeological record places it in
northern Jalisco during the Holocene (O. J. Polaco, personal
communication 2009). It ranged throughout Europe, Asia,
the Middle East, and even across north Africa. It presently
occupies approximately 5,000,000 km2 of the northwestern
portion of North America, 800,000 km2 of Europe (excluding
Russia), and much of northern Asia. The largest numbers
exist in Russia, USA (Alaska), and Canada. Many popula-
tions in Europe, and the more southerly portions of Asia and
North America are small and isolated (Servheen et al., 1999;
Swenson et al., 2000). Extirpation from east of the Missis-
sippi River occurs during the Pleistocene-Holocene transi-
tion (Graham & Lundelius, 1994). During the 20th century,
brown bears are extirpated from Mexico and a large portion
of the southwestern U.S. (Brown, 1985; Mattson & Merrill,
2002). Fossil records in North America are known from the
Late Pleistocene (post 25,000 radiocarbon years BP) into the
Holocene (Kurtén & Anderson, 1980).
Polar bears live throughout the ice-covered waters of the
circumpolar Arctic, and their range is limited by the southern
extent of sea ice (Schliebe et al., 2008). Although some oc-
cur in the permanent multi-year pack ice of the central Arctic
basin, they are most common in the annual ice over the
Figure 2: North American Quaternary Ursidae: (a) Pleistocene; (b) Holocene
Figuur 2: Noord-Amerikaanse kwartaire beren: (a) Pleistoceen; (b) Holoceen
a
b
SERGIO DE LA ROSASERGIO DE LA ROSA

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continental shelf and inter-island archipelagos that surround
the polar basin. Polar bears that have continuous access to
sea ice are able to hunt throughout the year. In those areas
where the sea ice melts completely each summer, polar bears
are forced to spend several months on land fasting on stored
fat reserves until freeze-up (Schliebe et al., 2008). North
American fossil remains are very rare and the spotty record
is primarily a Holocene one, with a very late Pleistocene re-
cord from Baillee Island in the western Northwest Territories
of Canada (Anderson, 1984; Vincent, 1989).
In regard to the North American Quaternary Ursidae
(sensu stricto), a rich bear fauna was formed by representa-
tives from two of the three known subfamilies, the Amer-
ican-endemic Tremarctinae and the world-wide distrib-
uted Ursinae (Ailuropodinae was not represented). North
American tremarctines included the Pleistocene spectacled
bear, Tremarctos oridanus (known from Early to Late
Pleistocene), and the short-faced bear Arctodus with two
species, A. pristinus (known from Early to Middle Pleisto-
cene; 2.6 to 0.5my) and A. simus (known from Middle to
Late Pleistocene; 1.8my to 11ky). Both species were known
from south to central Mexico (Ferrusquía et al., 2010). These
two species probably were the largest carnivores at their
time, each weighing around 350 kg. Arctodus simus was a
long-legged, short-bodied animal with a short face and broad
muzzle, while A. pristinus was smaller, had shorter limbs,
with a more elongated face (Kurtén & Anderson, 1980;
Anderson, 1984). Arctodus, like the polar bear, was domi-
nantly carnivorous in contrast to the omnivorous habits of
spectacled bears. Arctodus simus was considered an active
predator, being the most powerful predator of the American
Pleistocene (Kurtén & Anderson, 1980; Anderson, 1984).
Stable isotopic evidence, however, indicated it was more a
scavenger with a meat diet from diverse species (Matheus et
al., 2003; Pérez-Crespo et al., this volume). Arctodus went
extinct at the end of the Pleistocene.
Tremarctos oridanus was a widespread species that may
have survived until the early Holocene (Devil´s Den, Florida;
Kurtén &Anderson, 1980). Today, Tremarctos survives as the
spectacled bear, T. ornatus, in South America, leaving North
and Central America lacking this subfamily. The extinct
species is distinguished from the extant species by much
larger size and heavier proportions, with a tendency towards
a general reduction of the premolars and elongation of the
back molars (Anderson, 1984).
A juvenile skeleton of a spectacled bear, identied as
Tremarctos oridanus, comes from Cebada Cave, Belize
(Czaplewski et al., 2003). The record points to a narrowing
of its distribution at the very end of the Pleistocene. More
recently, bear specimens have been recorded from Hoyo
Negro cenote (a deep natural pit, or sinkhole, resulting from
the collapse of a doline or limestone bedrock that exposes
groundwater underneath) in Yucatan Peninsula (Chatters et
al., 2014). Although initially referred to the genus Tremarc-
tos, further study is warranted to determine their correct
taxonomical position (B. Schubert, personal communication,
2015).
Overall, at least seven bear species occur in the North
American Pleistocene (Figure 2a), while presently only
three are extant (Figure 2b). These three are in the subfamily
Ursinae, and considered endangered or threatened (Figure
3). The extinct species are in the subfamily Tremarctinae.
Currently, this subfamily is represented by a unique species
from the South American Andean region.
The extinction and extirpation of species as well as body
size shifts may be due to several factors. These factors
include the depletion in number of large herbivores, dimin-
ishing of nutritional quality of plants during climate change,
and competition with early peoples for food resources.
Despite these factors, bears from the subfamily Ursinae have
survived to the present.
HUMAN UTILIZATION
Few records are available for the possible use of bear by
Late Pleistocene peoples. In Mexico, black bear remains
appear to be associated with early peoples in central Mexico
(Tlapacoya, State of Mexico; Álvarez, 1969). Records of
tremarctinae bear for some cenotes are found in the Yucatan
Peninsula, and in particular Hoyo Negro, has a possible asso-
ciation with early human remains (Chatters et al., 2014).
More direct interaction between early peoples and bears is
documented at the Lubbock Lake Landmark (Texas, USA)
during the Late Pleistocene. Lubbock Lake is on the South-
ern High Plains of western Texas in a now dry stream valley
within the upper Brazos River basin. This multi-component
site is well-stratied, and the Late Pleistocene activity area
from which short-faced bear (Arctodus simus) remains came
(Clovis culture) is dated at 11,100 radiocarbon years BP
(Johnson, 1987). The short-faced bear remains exhibit two
categories of human modication that indicate very different
uses of the bear carcass. Butchery marks compose the rst
category and consist of pry marks and two types of cut
marks. Cut marks (narrow, single-stroke) on the metacarpals
indicate skinning. Cut marks (narrow, single-stroke and
wide, deep, multiple-stroke) on the radius indicate deesh-
ing. Pry marks on the proximal articular surface of the radi-
us indicate disarticulation. The wide, deep, multiple-stroke
marks indicate some resistance in the tissues and suggest
that the carcass was stiff. The carcass most likely was a
found one, scavenged by people (Johnson, 1987; Johnson &
Bement, 2009).
The second category is that of fracture-based utilitarian
technology. This technology employs a high velocity impact
technique (dynamic fracturing) as the fracturing method,
focused on intact fresh long bones (Johnson, 1985). Various
Figure 3: Quaternary defaunation of Ursidae in
North America
Figuur 3: Kwartaire verdwijning van beerachtigen
in Noord-Amerika

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production paths can be taken using this technique depend-
ing on the animal-size group. For large to medium sized
ungulates, the major production paths are marrow process-
ing and bone expediency tools. Expedient tool use was the
objective with the short-faced bear radius at the Lubbock
Lake Landmark. Dynamic fracturing of the radius created
two major portions (distal and proximal), each exhibiting
a helical fracture surface. Without further modication, the
proximal radius was used as a butchering tool, the tool bit
being the apex of the helical fracture. Use-wear evidence is
a combination of edge aking, differential polish, and worn
and rounded surfaces all along the apex. Scanning electron
microscopy analysis conrms the localized wear polishing,
edge rounding, and striae of the microsurface on the apex
(Johnson, 1990).
The fracture characteristics exhibited by the bear’s radius
indicated the bone was fractured while fresh. The bear
remains, then, may represent a human scavenging event of
a found, stiffened carcass of perhaps no more than a day or
two dead. People viewed the carcass in terms of subsistence
(meat procurement) and technology (raw material resource
for tool production), much the same as they viewed mam-
moth carcasses at this time (Johnson, 2005).
Currently, the only other known human-bear interaction is
for black bear (Ursus americanus) at Lehner Ranch (Arizo-
na, USA). Lehner Ranch is in southeastern Arizona within
the San Pedro River Valley, along Curry Draw that is one of
its tributaries. Numerous known Clovis-age sites are found in
this valley, primarily with a focus on mammoth (Mammuthus
columbi) and ancient bison (Bison antiquus) procurement
(Haynes & Huckell 2007). Lehner Ranch is a Clovis-age
site with different activity areas. Partially calcined teeth of a
3-month old bear cub come from a roasting pit. The context
suggests the bear cub was eaten (Saunders, 1977:51). Dated
charcoal from the surrounding occupation surface average
10,940 radiocarbon years BP (Taylor et al., 1996).
Native Americans increasingly utilized black bears
during the Holocene, particularly in the late Holocene upper
Midwest, e.g., Hopewell and Mississippian cultures (Styles,
2011). Despite this increased usage, black bears thrived
throughout their range. Human impact came in the form of
Euro-American settlement that brought habitat loss and hunt-
ing pressures to dramatically reduce their range and overall
population.
CONCLUDING REMARKS
In general, late Pleistocene humans and the more carniv-
orous bears may have been competitors for the same game
animals. The timing of carcass utilization or scavenging,
however, most likely would have been different to avoid
direct conict. Furthermore, people also ate short-faced bear
and black bear and utilized bones of the short-faced bear
for creating expedient butchering tools. Estimated weight
ranges for adult male short-faced bears (Arctodus simus) are
between 350 to 375 kg and adult females between 150-270
kg (Kurtén, 1967). Modern adult male black bears typical-
ly weigh between 57-250 kg and adult females between
41-170 kg (Hunter, 2011). Late Pleistocene black bears are
larger than their modern counterpart and could be consid-
ered a very large carnivore. Short-faced bear, however, is a
megacarnivore. Both bears would have been dangerous prey.
Bear hunting may not have been common during the late
Pleistocene, particularly with bears the size of Arctodus or
the black bear, but hunting or scavenging carcasses did occur
occasionally. That occasional activity, however, would not
have had an impact on bear populations.
ACKNOWLEDGMENTS
Data utilized for this research are from two main projects,
FAUNMAP and Mexican Mammal Quaternary Database
(CONABIO G-012). Felisa Aguilar and Sergio de la Rosa
kindly provided the maps and bear reconstructions, respec-
tively. Funds for traveling to the conference were kindly
provided by Eileen Johnson through her Texas Tech Uni-
versity Horn Professorship research fund. This manuscript
represents part of the ongoing Lubbock Lake Landmark
regional research into Quaternary grassland and ecological
changes in the Americas under the auspices of the Museum
of Texas Tech University.
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