|
|
|
|
Cave Bear
|
| |
|
| |
The Cave Bear (Ursus spelaeus) was a species of bear which lived in Europe during the Pleistocene and became extinct at the beginning of the Last Glacial Maximum about 27,500 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.
Discussion
Ask a question about 'Cave Bear' Start a new discussion about 'Cave Bear' Answer questions from other users |
Encyclopedia
The Cave Bear (Ursus spelaeus) was a species of bear which lived in Europe during the Pleistocene and became extinct at the beginning of the Last Glacial Maximum about 27,500 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 Pestera Ursilor (Bears' Cave) where 140 cave bear skeletons were discovered in 1983.
Discovery and history
Cave bear skeletons were first described in 1774 by Johann Freiderich Esper in his book Newly Discovered Zoolites of Unknown Four Footed Animals. Originally thought to belong to dragons, unicorns, apes, canids or felids, Esper postulated that they actually belonged to polar bears. 20 years later, Rosenmüller, an anatomist at the Leipzig University gave the species its binomial name. Cave bear bones were so numerous, that most researchers held little respect for them. During WWI, large amounts of cave bear bones were used as phosphates, leaving behind little more than skulls and leg bones.
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.
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. 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.
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). Some experts suggest weights of up to 1,000 kilograms (2,200 pounds) for full grown males. 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. 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.
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. 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 Pestera 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. 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 its contemporary, the smaller Eurasian Brown Bear.
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. 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. Cave bear longevity is unknown, though it has been estimated that they seldom exceeded 20 years of age. 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.
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. Neanderthals, 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 Neanderthal 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 Neanderthals 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.
Cause of extinction
Recent reassessment of fossils indicate the cave bear probably died out 27,800 years ago. Though the reason is still disputed, the timing supports habitat loss due to climate change as responsible. Compared with other megafaunal species that also became extinct during the last Glacial Maximum, the cave bear had a more specialized diet of high quality plants and a relatively restricted geographical range which is suggested as an explanation as to why it died out so much earlier than the rest. Certain experts 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.
External links
|
| |
|
|
