Testing Alternative Hypotheses for Patterns of Tooth Breakage in Carnivores

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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.