Clinic for Zoo Animals, Exotic Pets and Wildlife, Vetsuisse Faculty, University of Zurich, Zurich, Switzerland.
Department of Zoology and Entomology, University of the Free State, Bloemfontein, South Africa.
PLoS One. 2020 Jun 15;15(6):e0234826. doi: 10.1371/journal.pone.0234826. eCollection 2020.
Feeding practice in herbivorous mammals can impact their dental wear, due to excessive or irregular abrasion. Previous studies indicated that browsing species display more wear when kept in zoos compared to natural habitats. Comparable analyses in tapirs do not exist, as their dental anatomy and chewing kinematics are assumed to prevent the use of macroscopic wear proxies such as mesowear. We aimed at describing tapir chewing, dental anatomy and wear, to develop a system allowing comparison of free-ranging and captive specimens even in the absence of known age. Video analyses suggest that in contrast to other perissodactyls, tapirs have an orthal (and no lateral) chewing movement. Analysing cheek teeth from 74 museum specimens, we quantified dental anatomy, determined the sequence of dental wear along the tooth row, and established several morphometric measures of wear. In doing so, we showcase that tapir maxillary teeth distinctively change their morphology during wear, developing a height differential between less worn buccal and more worn lingual cusps, and that quantitative wear corresponds to the eruption sequence. We demonstrate that mesowear scoring shows a stable signal during initial wear stages but results in a rather high mesowear score compared to other browsing herbivores. Zoo specimens had lesser or equal mesowear scores as specimens from the wild; additionally, for the same level of third molar wear, premolars and other molars of zoo specimens showed similar or less wear compared specimens from the wild. While this might be due to the traditional use of non-roughage diet items in zoo tapirs, these results indicate that in contrast to the situation in other browsers, excessive tooth wear appears to be no relevant concern in ex situ tapir management.
食草哺乳动物的饲养方式会影响其牙齿磨损，这是由于过度或不规则的磨损造成的。以前的研究表明，与自然栖息地相比，动物园中的食草动物表现出更多的磨损。在貘类中，没有类似的分析，因为它们的牙齿解剖结构和咀嚼运动学被认为可以防止使用宏观磨损代理物，如Mesowear。我们的目的是描述貘的咀嚼、牙齿解剖结构和磨损，开发一种系统，即使在没有已知年龄的情况下，也能比较自由放养和圈养的标本。视频分析表明，与其他奇蹄目动物不同，貘的咀嚼运动是 orthal（而不是 lateral）的。通过对 74 件博物馆标本的臼齿进行分析，我们量化了牙齿解剖结构，确定了沿牙齿排列的磨损顺序，并建立了几个磨损的形态测量指标。在这样做的过程中，我们展示了貘的上颌牙齿在磨损过程中明显改变了它们的形态，在磨损较少的颊侧和磨损较多的舌侧牙尖之间形成了高度差，并且定量磨损与出牙顺序相对应。我们证明，Mesowear 评分在初始磨损阶段表现出稳定的信号，但与其他食草动物相比，结果显示出相当高的 Mesowear 评分。动物园标本的 Mesowear 评分低于或等于野生标本；此外，对于相同程度的第三磨牙磨损，动物园标本的前磨牙和其他磨牙的磨损与野生标本相似或更小。虽然这可能是由于动物园中的貘传统上使用非粗饲料食物，但这些结果表明，与其他食草动物的情况相反，过度的牙齿磨损似乎不是圈养貘管理中的一个相关问题。
