Mammal Study
Volume 34, Issue 1, 2009
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Original papers
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Three-Dimensional Reconstruction of the Xenarthrous Process of the Thoracic and Lumber Vertebrae in the Giant Anteater
View Description Hide DescriptionAbstract.The presacral vertebra of anteaters was examined by three-dimensional CT image analysis of the xenarthrous processes peculiar to the Order Xenarthra. The anteater is equipped with two following articulations in addition to the normal zygapophysial articulation. The dorsal xenarthrous process of the former vertebra articulates to the ventral area of the base of the mammillary process in the later vertebra. The pocket-like structure in the ventral area of the mammillary process receives the dorsal and ventral xenarthrous processes of the former vertebra. The complicated articulations do not obstruct the ability of the giant anteater to flex dorsally and laterally, however aids flexibility and strengthens the caudal thoracic and lumber regions of the animal. The xenarthrous processes and articulations may function as a supporter of the body weight during the bipedal standing posture when the anteater destroys the nests of ants and termites and protects itself from the enemies.
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Absence of the Guttural Pouch in a Newborn Indian Rhinoceros Demonstrated by Three-Dimensional Image Observations
View Description Hide DescriptionAbstractCT scanning and its related three-dimensional image techniques were applied for a carcass head of a newborn Indian rhinoceros (Rhinoceros unicornis) to clarify if the guttural pouch is well-developed or not in the early growth stages of this species. Observations from the sections of the CT three-dimensional reconstructed image reveal that the guttural pouch is not present around the stylohyoid bone in a new born Indian rhinoceros. Since the absence of the guttural pouch has been confirmed also in adult rhinoceros, we can point out that the guttural pouch does not disappear during the growth stages, but is originally absent in the newborn. Although the well-developed guttural pouch in the horse and ass has attracted anatomists, we can conclude that the guttural pouch is not commonly observed in the perissodactyls, but in a few species of Equus, and that the guttural pouch is adapted only to restricted roles in the smaller taxa within perissodactyls.
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Effectiveness of Newly-Designed Electric Fences in Reducing Crop Damage by Medium and Large Mammals
View Description Hide DescriptionAbstract.Many mammal species can cause crop damage simultaneously at one location; therefore, we designed and tested three fence types that targeted medium and large mammals. Ten mammal species were targeted (Japanese hare, raccoon dog, red fox, Japanese marten, masked palm civet, Eurasian badger, Asiatic black bear, wild boar, sika deer, and Japanese macaque). All three fences were electric and an expanded metal lath carried the current. To prevent invasions through lower gaps, the gap between the expanded metal lath and the ground surface was closed using a corrugated polyvinyl chloride sheet as an insulating material. After the fences were constructed, infrared-triggered cameras were set up both inside and outside the fences. All three fences prevented invasion by the targeted species. Overall, these fences had high practical value for nine of the targeted species; the exception was the Asiatic black bear, which was observed only once.
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Effects of Size on the Skull Shape of the Bottlenose Dolphin (Tursiops truncatus)
View Description Hide DescriptionAbstract.We measured 145 bottlenose dolphin skulls to examine the effects of size on skull shape. We found that the rostral length and the width of the temporal fossa showed highly positive allometry. These differences, as a result of size, reflect the growth of the feeding apparatus. The positive allometry of the rostral length implies an extension of the range for food catching and an increase in mouth-closing speed. The positive allometry of the temporal fossa width reflects the development of the temporal muscle. On the other hand, the positive allometry of both the rostral length and the temporal fossa width seem to indicate a contradictory effect on occlusal force. However, the occlusal force estimated by bony characters increased by the condylobasal length. These trends were observed not only in immature specimens but also in mature specimens of different sizes. This fact means that the change of the skull shape in immature specimens is caused by the development of the feeding apparatus, while that the variation in mature specimens of different sizes is due to a result of ontogenetic changes. Therefore, it is suggested that mature specimens also have morphological variation depending on size, and this fact sometimes confuses the taxonomic studies based on the morphological data.
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Short communications
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A Peculiar Cusp on the Fourth Upper Premolar of the Japanese Water Shrew Chimarrogale platycephala
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Classification of the Seminiferous Epithelial Cycle in the Sika Deer (Cervus nippon)
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Fruiting Phenology and its Effect on Fruit Feeding Behavior of Asiatic Black Bears
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