Testing Alternative Hypotheses for Patterns of Tooth Breakage in Carnivores

[405916]范·瓦尔肯堡一颗重要牙齿的全部或部分脱落，如犬齿，对捕食者来说似乎是严重的伤害。严重钝钝的犬齿在杀戮和威胁中都是较差的武器，而破碎的颊齿则是切肉和咬碎骨头的糟糕工具。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，牙齿断裂是有规律发生的，其中犬齿是最容易断裂的。此外，对更新世Rancho La brea沥青坑的北美食肉动物牙齿断裂的平行研究记录了四种大型物种的大量牙齿断裂：可怕的狼，剑齿虎，美洲狮和土狼。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，牙齿更容易断裂，而当动物饥饿和猎物难以获得时，吃骨头更常见。因此，据推测，这四个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。在晚更新世时期，大型食肉动物的物种多样性和种群密度都比现在大，这加剧了它们之间的竞争。尽管越来越多的人吃骨头似乎是化石动物断牙数量增加的一个可能原因，但这并不是唯一可能的解释。其他包括更大的猎物尺寸，不同的杀戮行为，或更大的捕食者尺寸。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（哺乳动物目食肉动物的成员）。利用已建立的博物馆和收藏品，将对47种食肉目动物（如黄鼠狼、浣熊、猫、狗、鬣狗、熊）的牙齿断裂进行评估，这些动物在饮食、猎物大小和体重方面存在很大差异。每个物种平均要检查60个头骨或1000多颗牙齿。牙齿断裂发生率与五个因素之间的关系（进食行为的各个方面，如猎物的大小，捕猎的频率，消耗的骨头数量）将通过统计来探索。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只，是因为初步数据表明，每个物种的不同种群吃的骨头或肉的数量不同，这种饮食上的差异可能会影响一生中折断牙齿的数量。对现代物种的研究将伴随着对来自7个更新世化石矿床、4个旧大陆和3个新大陆的捕食者牙齿断裂的研究。这些化石遗址将被用来测试拉布雷亚牧场四种食肉动物牙齿断裂的高频率是否是更新世其他地方大型食肉动物的典型特征。这项拟议的研究是对任何哺乳动物中牙齿损伤频率的第一次大规模调查。它将为许多体型和饮食习惯差异很大的物种积累一个关于牙齿磨损和牙齿断裂率的大型数据库。这项研究意义重大，因为它将提供：关于自然发生的伤害率的数据；2)牙齿功能与进化的新视角；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.