Reconstructing cave bear paleoecology from skeletons: a cross-disciplinary study of middle Pleistocene bears from Yarimburgaz Cave, Turkey
Reconstructing cave bear paleoecology from skeletons: a cross-disciplinary study of middle Pleistocene bears from Yarimburgaz Cave, Turkey
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从骨骼重建洞熊古生态：对土耳其 Yarimburgaz 洞穴中更新世熊的跨学科研究
DOI：
10.1017/s0094837300019989
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发表时间：
1998
期刊：
影响因子：
2.7
通讯作者：
J. Quade
中科院分区：
文献类型：
--
作者：
M. Stiner;H. Achyuthan;Güven Arsebük;F. Howell;S. Josephson;K. Juell;J. Pigati;J. Quade
洞熊是熊属的一个已灭绝的亚属（Spelearctos），在更新世中期和晚期，它们的用途非常广泛，可以居住在北方的大片地区，但它们已经进化出一种特殊的牙列，强调研磨功能，这意味着它们对坚韧的纤维食物（即，植物）。然而，同位素研究在洞熊饮食方面产生了相互矛盾的结果，通常没有考虑样本的来源或埋藏学和形态学证据可能对饮食解释造成的可能矛盾。洞熊的习性可能会因环境而有所不同，而它们这样做的能力的极限仍然未知。如果古生物学研究的更大目标是重建洞熊物种的适应性，那么必须密切跟踪种群之间的变异和共性，并在个案的基础上对现有的不同证据进行审查。显然，没有任何一种分析技术可以做到这一点。通过举例的方式，我们提出了一个跨学科的合作，结合骨骼，同位素和埋藏的方法来研究古生态学的熊组合在土耳其西北部的Yarimburgaz洞穴的结果。关于现代熊的饮食、冬眠和种群结构之间联系的参考信息为调查提供了测试意义。骨测量技术表明，在样本中存在两种共存的中更新世熊类--洞熊的一种--熊和熊。北极熊或棕熊-前者在样本中大量存在，后者则很少见。熊的消耗性死亡模式和它们的骨骼状况表明，大多数或所有动物在冬眠的情况下死于洞穴中的非暴力原因。这项研究还阐明了该地区洞熊种群的几个特征。骨骼测量技术显示，成年洞熊的性别比例只是稍微偏向雌性。这种模式位于现代熊类所有可能结果的一个极端附近，只能反映出对季节性植物和无脊椎动物的强烈饮食依赖，表明冬眠是两性的关键越冬策略;结果特别与经常强调大型游戏（狩猎或清除）作为冬季食物来源的可能性相矛盾。成年洞熊牙齿的磨损和断裂的性质表明，食物经常是从神秘的来源获得的，需要挖掘和窥探，并且需要广泛的咀嚼，导致老年个体的一些颊齿冠完全消失。生活中牙齿损伤的模式证实了成年人性别比例的饮食影响，并主张饮食中富含坚韧的研磨材料，如坚果，块茎和相关的砂砾。洞穴和棕熊牙釉质的碳和氧同位素组成几乎是相同的，没有证据表明这两个物种有强烈的海洋信号，尽管洞穴靠近现代的马尔马拉海河口;由于蛋白质保存不好，无法检查氮同位素比。同位素结果表明，这两种熊在中更新世期间在该地区是高度杂食性的，几乎所有的食物都来自陆地和淡水栖息地。骨骼病变，通常源于创伤，发生在一些成年熊，证明了这个化石种群中一些个体的寿命很长。Yarimburgaz洞穴熊也表现出巨大的两性异形，基于承重腕骨的尺寸，成年雄性的体重大约是成年雌性的两倍。
Cave bears, an extinct subgenus (Spelearctos) of Ursus, were versatile enough to inhabit large areas of the northern hemisphere during the middle and late Pleistocene, yet they had evolved a specialized dentition that emphasized grinding functions, implying a heavy dietary reliance on tough, fibrous foods (i.e., plants). Isotope studies have yielded conflicting results on cave bear diet, however, often without consideration of the provenance of the samples or the possible contradictions that taphonomic and morphologic evidence might pose to dietary interpretations. It is likely that cave bear habits varied somewhat in response to environmental circumstance, and the limits on their abilities to do so remain unknown. If the larger goal of paleontological inquiry is to reconstruct the adaptations of cave bear species, then variation and commonalities among populations must be tracked closely, and the disparate lines of evidence currently available examined together on a case by case basis. Clearly, no single analytical technique can achieve this. By way of example we present the results of a cross-disciplinary collaboration that combines osteometric, isotopic, and taphonomic approaches to studying the paleoecology of a bear assemblage from Yarimburgaz Cave in northwest Turkey. Reference information on the linkages between diet, hibernation, and population structure in modern bears provides test implications for the investigation. Osteometric techniques demonstrate the presence of two coextant middle Pleistocene bear species in the sample–Ursus (Spelearctos) deningeri, a form of cave bear, and U. arctos or brown bear–the former abundant in the sample, the latter rare. An attritional mortality pattern for the bears and the condition of their bones show that most or all of the animals died in the cave from nonviolent causes in the context of hibernation. The study also elucidates several characteristics of the cave bear population in this region. Osteometric techniques show that the adult sex ratio of the cave bears is only slightly skewed toward females. This pattern lies near one extreme of the full range of possible outcomes in modern bear species and can only reflect a strong dietary dependence on seasonally available plants and invertebrates, showing that hibernation was a crucial overwintering strategy for both sexes; the results specifically contradict the possibility of regular, heavy emphasis on large game (hunted or scavenged) as a winter food source. The nature of wear and breakage to the adult cave bear teeth indicates that food frequently was obtained from cryptic sources, requiring digging and prying, and that extensive mastication was necessary, leading to complete obliteration of some cheek tooth crowns in old individuals. The patterns of tooth damage during life corroborate the dietary implications of the adult sex ratio and also argue for a diet rich in tough, abrasive materials such as nuts, tubers, and associated grit. The carbon and oxygen isotopic compositions of cave and brown bear tooth enamel from the site are virtually identical, and there is no evidence of a strong marine signal in either species, despite the cave's proximity to a modern estuary of the Sea of Marmara; nitrogen isotope ratios could not be examined because of poor protein preservation. The isotope results suggest that both bear species were highly omnivorous in the region during the middle Pleistocene and obtained nearly all of their food from terrestrial and fresh-water habitats. Bone pathologies, usually originating from trauma, occur in some of the adult bears, testifying to long lifespans of some individuals in this fossil population. The Yarimburgaz cave bears also exhibit great size dimorphism between the sexes, based on weight-bearing carpal bone dimensions, with adult males attaining roughly twice the body mass of adult females.