Testing Alternative Hypotheses for Patterns of Tooth Breakage in Carnivores

9405916货车瓦肯堡 一颗重要的牙齿（如犬齿）的全部或部分缺失，对捕食者来说似乎是一个严重的伤害。严重钝化的犬齿无论是用于杀戮还是威胁目的都是低劣的武器，而破碎的颊齿则是用于切肉和压碎骨头的拙劣工具。然而，最近对几种现存大型食肉动物牙齿断裂发生率的调查显示，断裂经常发生，犬齿是最容易断裂的。此外，一项对更新世Rancho La brea焦油坑的北美捕食者牙齿断裂的平行研究记录了四个大型物种的牙齿断裂数量非常高：可怕的狼，剑齿猫，美洲狮和郊狼。牙齿断裂的频率是现代物种的三到五倍。根据初步数据，有人认为，当动物吃骨头时，牙齿更容易折断，当动物饥饿而猎物难以获得时，吃骨头更常见。因此，有人假设这四种更新世物种比现代大型食肉动物更经常吃骨头，更充分地消耗猎物的尸体。这种更大的骨骼消耗可能是由于这些更新世动物之间的竞争比我们目前观察到的更激烈。在更新世晚期，大型捕食者的物种多样性和可能的种群密度都比现在大，加剧了它们之间的竞争。 虽然吃骨头的增加似乎是化石动物中牙齿断裂数量增加的可能原因，但这不是唯一可能的解释。其他包括更大的猎物大小，不同的杀戮行为，或更大的捕食者大小。这一建议的目的是提高我们对哺乳动物牙齿断裂原因的理解，特别是食肉动物（哺乳动物食肉目的成员）。利用已建立的博物馆和收藏品，将对食肉目47种动物的牙齿断裂进行评估（例如，鼬鼠、浣熊、猫、狗、鬣狗、熊）的饮食、猎物大小和体重差异很大。每个物种平均将检查60个头骨或1000多颗牙齿。牙齿断裂发生率与五个因素（摄食行为方面，如猎物大小，狩猎频率，消耗的骨量）之间的关联将通过统计学进行探讨。 此外，包括土狼、灰狼和美洲狮在内的11个物种将被用于研究其地理范围内物种的牙齿骨折发生率。之所以选择这11个物种，是因为初步数据表明，每个物种中的不同种群吃的骨头或肉的数量不同，这种饮食差异可能会影响一生中牙齿断裂的数量。对现代物种的研究将伴随着对来自七个更新世化石矿床的捕食者牙齿断裂的研究，四个旧世界和三个新世界。这些化石地点将被用来测试是否在兰乔拉布雷亚的四个食肉动物的牙齿断裂的高频率是典型的大型食肉动物在更新世的其他地方。 这项拟议中的研究是第一次大规模调查任何哺乳动物的牙齿损伤频率。它将积累大量关于牙齿磨损率和牙齿断裂率的数据，这些数据涉及许多在体型和饮食习惯上差异很大的物种。这项研究意义重大，因为它将提供：10关于自然发生的伤害率的数据; 2）关于牙齿功能和进化的新视角; 3）分析过去社区的新工具。

9405916 van Valkenburgh The complete or partial loss of an important tooth, such as a canine, would seem a serious injury for a predator. Severely blunted canine teeth are inferior weapons for both killing and threat purposes, and broken cheek teeth are poor tolls for slicing meat and crushing bone. However, recent surveys of tooth fracture incidence in several living species of large carnivores have revealed that breakage occurs regularly, and that canine teeth are among the most likely to break. Furthermore, a parallel study of tooth breakage in North American predators of the Pleistocene Rancho La brea tar pits documented very high numbers of broken teeth in four large species: the dire wolf, sabertooth cat, American lion and coyote. Tooth fracture frequencies were three to five times that observed for modern species. Based on preliminary data, it was argued that teeth are more likely to break when animals eat bone, and that bone-eating is more common when animals are hungry and prey is difficult to acquire. Thus, it was hypothesized that the four Pleistocene species ate bone more often and consumed the carcasses of their prey more fully than do modern large carnivores. This greater bone consumption was likely due to greater competition among these Pleistocene animals than we observe at present. Both the species diversity and probably the population densities of large predators were greater during the late Pleistocene than at present, intensifying the levels of competition among them. Although increased bone eating seems a likely cause of the greater numbers of broken teeth in the fossil animals, it is not the only possible explanation. Others include larger prey size, different killing behaviors, or larger predator size. It is the intent of this proposal to improve our understanding of the causes of tooth fracture in mammals in general , and carnivorans (members of the mammalian order Carnivora), in particular. Using established museum in gen eral, and collections, tooth breakage will be assessed in 47 species of the order Carnivora ( e.g., weasels, racoons, cats, dogs, hyenas, bears) that vary widely in diet, prey size, and body mass. On average, 60 skulls or more than 1000 teeth will be examined for each species. The association between tooth breakage incidence and five factors (aspects of feeding behavior such as prey size, how often they hunt, amount of bone consumed) will be explored with statistics. In addition, eleven species, including the coyote, gray wolf, and puma, will be used for a study of tooth fracture incidence within species across their geographic range. All eleven were chosen because preliminary data indicate that different populations within each species eat different amounts of bone or meat and this dietary variation might affect the number of teeth broken in life. The study of modern species will be accompanied by a study of tooth breakage in predators from seven Pleistocene fossil deposits, four Old World and three New World. These fossil sites will be used to test whether the high frequencies of tooth breakage in the four predators of Rancho La Brea are typical of large predators elsewhere during the Pleistocene. The proposed study is the first large-scale survey of the frequency of dental injury in any mammalian order. It will amass a large data base on rates of tooth wear and tooth breakage for a number of species that vary greatly in body size and food habits. The study is significant because it will provide: 10 data on naturally occurring rates of injury; 2) a new perspective on tooth function and evolution; 3) new tools for the analysis of past communities.