Cave bear

Taxobox
name = Cave Bear
fossil_range = Middle to Late Pleistocene

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image_width = 240px
image_caption = Cave Bear skeleton
regnum = Animalia
phylum = Chordata
classis = Mammalia
ordo = Carnivora
familia = Ursidae
genus = "Ursus"
species = "U. spelaeus"
binomial = "Ursus spelaeus"
binomial_authority = Rosenmüller, 1794

The Cave Bear ("Ursus spelaeus") was a species of bear which lived in Europe during the Pleistocene and became extinct at the end of the last ice age about 20,000 years ago.Both the name "Cave Bear" and the scientific name "spelaeus" derive from the fact that fossils of this species were mostly found in caves, indicating that this species spent more time in caves than the Brown Bear, which only uses caves for hibernation. Consequently, in the course of time, whole layers of bones, almost entirely those of cave bears, were found in many caves.

Many caves in Europe have skeletons of cave bears on display, for example the "Heinrichshöhle" in Hemer or the "Dechenhöhle" in Iserlohn, Germany. In Romania, there is a cave called Peştera Urşilor (Bears' Cave) where 140 cave bear skeletons were discovered in 1983. [http://www.personal.psu.edu/users/w/x/wxk116/cavebears/]

Range and habitat

The cave bear's range stretched across Europe; from Spain to Eurasia, from Italy and Greece to Belgium, the Netherlands and possibly Great Britain, across a portion of Germany through Poland, then south into Hungary, Romania and parts of Russia. There have been no traces of cave bears living in northern Britain, Scandinavia or the Baltic countries, which were covered in extensive glaciers at the time. The largest numbers of cave bear remains have been found in Austria, Switzerland, southern Germany, northern Italy, northern Spain, Croatia, Hungary and Romania. The huge number of bones found in south, central and east Europe has led some scientists to think that Europe may have once had literal herds of cave bears. Some however point out that though some caves have thousands of bones, they were accumulated over a period of 100,000 years or more, thus requiring only two deaths in a cave per year to account for the large numbers.cite book | author = Bieder, Robert | url = http://www.amazon.com/Bear-Reaktion-Books-Robert-Bieder/dp/1861892047/ref=sr_1_1?ie=UTF8&s=books&qid=1203593352&sr=1-1| title = Bear | year = 2005 | pages = pp.192 | id = ISBN 1861892047 ]

The cave bear inhabited low mountainous areas, especially in regions rich in limestone caves. They seemed to avoid open plains, preferring forested or forest-edged terrains.

Evolution

The cave bear is thought to be descended from the plio-pleistocene Etruscan bear ("Ursus etruscus") through the Deninger's bear ("Ursus deningeri") of the Pleistocene half a million years ago. However, Loreille "et al." (2001) demonstrate that cave bears split largely before the lineages of brown bears around 1.2 million years ago. [cite journal |last=Loreille |first=Odile |authorlink= |coauthors="et al." |year=2001 |month= |title=Ancient DNA analysis reveals divergence of the cave bear, "Ursus spelaeus", and brown bear, "Ursus arctos", lineages |journal=Current Biology |volume=11 |issue=3 |pages=200–203 |doi=10.1016/S0960-9822(01)00046-X |url= |accessdate= |quote= ] Cave bears found in different regions vary in age and evolutionary advancement, thus facilitating investigations into their development.The three anterior premolars were gradually reduced, then disappeared. For the largely vegetarian cave bear, the three premolars of its ancestors became redundant. In a fourth of the skulls found in the Conturines, the third premolar is still present, while the other more evolved specimens elsewhere lack it. The fourth premolar developed into a molar. The last remaining premolar became conjugated with the true molars, enlarging the crown and granting it more cusps and cutting borders. This phenomenon known as molarization improved the mastication capacities of the molars, facilitating the processing of tough vegetation. This allowed the cave bear to gain more energy for hibernation while eating less than its ancestors. [ [http://www.altabadia.it/orsispelei/evoluzione_i.htm Gli orsi spelèi delle Conturines/ Ursus Spelaeus ] ]

Description

Anatomy

The cave bear had a very broad, domed skull with a steep forehead. Its stout body had long thighs, massive shins and in-turning feet, making it similar in skeletal structure to the brown bear. The average weight for males was 400 kilograms (880 pounds).cite book | author = Brown, Gary | url = http://www.amazon.com/Great-Bear-Almanac-Gary-Brown/dp/1558214747/ref=sr_1_2?ie=UTF8&s=books&qid=1203593457&sr=1-2| title = Great Bear Almanac | year = 1996 | pages = pp.340 | id = ISBN 1558214747] Certain experts suggest greater weights of 500-600 kilograms (1,102-1,323 pounds).cite book | author = Pastoureau, Michel | title = L’ours; Histoire d’un roi dechu | year = 2007 | pages = pp.419 | id = ISBN 202021542X ] Males were larger than females. 90% of cave bear skeletons in museums are male, due to a misconception that the female skeletons were merely "dwarfs". Cave bears grew larger during glaciations and smaller during interglacials, probably to adjust heat loss rate.cite book | author= Macdonald, David | url = http://www.amazon.com/Velvet-Claw-Natural-History-Carnivores/dp/0563208449/ref=sr_1_2?ie=UTF8&s=books&qid=1203593491&sr=1-2| title=The Velvet Claw | year=1992 | pages= 256 | id= ISBN 0563208449 ] Cave bears of the last ice age lacked the usual 2-3 premolars present in other bears; to compensate, the last molar is very elongated, with supplementary cusps. [ [http://www.altabadia.it/orsispelei/nozioni_i.htm Gli orsi spelèi delle Conturines/ Ursus Spelaeus ] ]

Dietary habits

The morphological features of their chewing apparatus suggest both herbivorous behaviour and important adaptations to a tough vegetarian diet. Results obtained on the stable isotopic yield of cave bear bones are interpreted as indicators of a largely vegetarian diet.cite web | url = http://www.geo.auth.gr/12icbs/proceedings/pinto.pdf| title = COMPARATIVE DENTAL MICROWEAR ANALYSIS OF CAVE BEARS URSUS SPELAEUS Rosenmüller , 1794 AND BROWN BEARS URSUS ARCTOS Linnaeus , 1758 | work = | publisher = Scientific Annals, School of Geology Aristotle University of Thessaloniki (AUTH) | accessdate = 2008-01-11] The bones of central and western European cave bears matched those of vegetarians in having low levels of nitrogen-15, which is accumulated by meat eaters. However, several cave bear sites in the Peştera cu Oase in the southwestern tip of the Carpathian mountains have shown that the cave bears of that region may have been largely carnivorous, due to higher levels of nitrogen-15 in their bones. This behavior is also evident from very large cave bear tooth marks on young cave bear skulls in Yarimburgaz Cave in western Turkey.cite web | url = http://www.foxnews.com/story/0,2933,320971,00.html| title = Prehistoric Cave Bears Weren't So Cuddly After All | work = | publisher = FOXNews | accessdate = 2008-01-11] It is thought that cannibalistic scavenging constituted a minor part of an otherwise chiefly vegetarian diet, thus leaving no identifiable isotopic signature in the bones of central and western European specimens. Dental Microwear Analyses indicates that the cave bear may have fed on a greater quantity of bone than it's contemporary, the smaller Eurasian Brown Bear.cite web | url = http://www.geo.auth.gr/12icbs/proceedings/pinto.pdf| title = COMPARATIVE DENTAL MICROWEAR ANALYSIS OF CAVE BEARS URSUS SPELAEUS Rosenmüller , 1794 AND BROWN BEARS URSUS ARCTOS Linnaeus , 1758 | work = | publisher = Scientific Annals, School of Geology Aristotle University of Thessaloniki (AUTH) | accessdate = 2008-01-11]

Mortality

Death during hibernation was a common end for cave bears, mainly befalling specimens that failed ecologically during the summer season through inexperience, sickness or old age.cite book | author = Kurten, Bjorn | url = http://www.amazon.com/Pleistocene-Mammals-Europe-Bjorn-Kurten/dp/0202309533/ref=sr_1_1?ie=UTF8&s=books&qid=1203593539&sr=1-1| title = Pleistocene Mammals of Europe | year = 1968 | pages = pp.325 | id = ISBN 0202309533] Some cave bear bones show signs of numerous different ailments, including fusion of the spine, bone tumours, cavities, tooth resorption, necrosis (particularly in younger specimens), nematodes, osteomyelitis, periostitis, rickets and kidney stones. Male cave bear skeletons have been found with broken baculums, probably due to fighting during breeding season.cite book | author = Kurten, Bjorn | title = Pleistocene Mammals of Europe | year = 1968 | pages = pp.325 | id = ISBN 0202309533] Cave bear longevity is unknown, though it has been estimated that they seldom exceeded 20 years of age.cite book | author = Bieder, Robert | title = Bear | year = 2005 | pages = pp.192 | id = ISBN 1861892047 ] Paleontologists doubt adult cave bears had any natural predators, save for pack hunting wolves and cave hyenas which would probably have attacked sick or infirm specimens. Cave hyenas are thought to be responsible for the dis-articulation and destruction of some cave bear skeletons. Such large carcasses were an optimal food resource for the hyenas, especially at the end of the winter, when food was scarce.cite web | url = http://64.233.183.104/search?q=cache:TH2j9N58LoQJ:nts1.cgu.cz/bulletin/contents/2006/vol81no4/237_diedrich.pdf+Crocuta+spelaea&hl=en&ct=clnk&cd=13| title = Prey deposits and den sites of the Upper Pleistocene hyena Crocuta crocuta spelaea (Goldfuss, 1823)in horizontal and vertical caves of the Bohemian Karst| work = CAJUSG. DIEDRICH & KARELŽÁK| publisher = | accessdate = 2008-01-20]

Cave bear worship

Collections of bear bones at several widely dispersed sites suggest that Neanderthals may have worshipped cave bears, especially at Drachenlock, in Switzerland, where a stone chest was discovered with a number of bear skulls stacked upon it. Neandertals, who also inhabited the entrance of the cave, are believed to have built it. A massive stone slab covered the top of the structure. At the cave entrance, seven bear skulls were arranged with their muzzles facing the cave entrance, while still deeper in the cave, a further six bear skulls were lodged in niches along the wall. Next to these remains were bundles of limb bones belonging to different bears. Consequently, it was at this site that the supposed symbol of the "Cult of the Cave Bear" was found. This consisted of the skull of a three-year-old bear pierced in the cheek by the leg-bone of younger bear. The arrangement of these bones of different bears are not believed to have happened by chance.

A similar phenomenon was encountered in Regourdou, southern France. A rectangular pit contained the remains of at least twenty bears, covered by a massive stone slab. The remains of a Neandertal lay nearby in another stone pit, with various objects, including a bear humerus, a scraper, a core, and some flakes, which were interpreted as grave offerings.

The unusual finding in a deep chamber of Basua Cave in Savona, Italy, is thought to be related to cave bear worship, as there is a vaguely zoomorphic stalagmite surrounded by clay pellets. It was apparently used by Neandertals for a ceremony, the fact that bear bones lay scattered on the floor further suggested that this was likely to have had some sort of ritual purpose. [ [http://www.neandertals.org/ritual.html Burial, Ritual, Religion, and Cannibalism ] ]

Cause of extinction

The cave bear probably died out 10,000 years ago, though the reason is still disputed. It has been claimedwho that habitat loss due to climate change was responsible. Certain expertswho dispute this claim, as the cave bears had survived multiple times of climate change. Overhunting by humans has been largely dismissed because human populations at the time were too small to pose a serious threat to the cave bear's survival, though there is proof that the two species may have competed for living space in caves. One theory proposed by late paleontologist Bjorn Kurten states that the cave bear populations were fragmented and under stress even before the advent of the glaciers.

Gene recovery

In May 2005, scientists in California succeeded in recovering and decoding DNA of a cave bear that lived between 42,000 and 44,000 years ago. The procedure used genomic DNA extracted from the animal's tooth, made use of powerful new computing technology developed for the human genome project. Sequencing the DNA directly (rather than first replicating it with the polymerase chain reaction), the scientists were able to recover 21 cave bear genes.Cite journal|author=Noonan, James P.; "et al." |title=Genomic Sequencing of Pleistocene Cave Bears |year=2005 |journal=Science |volume=309 |issue=5734 |pages=597–599 |doi=10.1126/science.1113485 |pmid=15933159 ]

References

External links

* [http://www.personal.psu.edu/users/w/x/wxk116/cavebears/ Cave Bears -- The War for Habitable Caves]
* [http://www.showcaves.com/english/ro/showcaves/Ursilor.html Show Caves of Romania]