Assemblages of mammal skeletal remains provide a powerful tool for censusing wildlife populations to establish zoological baselines required for evaluating biogeographic trends over varying timescales. Caves provide an ideal depositional setting to preserve these skeletal remains despite potential time averaging and taphonomic filtering. We describe a Holocene paleontological assemblage from Boomerang Cave in the Bear River Range of Cache County, northern Utah, United States, at an elevation of 2,231 m, and at the boundary between the Great Basin and Rocky Mountain biogeographic provinces. We analyzed 1,228 surface-collected specimens from six areas within the cave, and identified a minimum of 22 nonoverlapping mammalian taxa, comprising all size classes present in the region. Compared to museum records for mammals from the Bear River Range and individuals trapped or observed in the vicinity of the cave, specimen-based rarefaction demonstrates that our assemblage captures most of the mammalian diversity expected in the area. This is particularly apparent for carnivorans and soricids, which are particularly well-represented in the Boomerang Cave assemblage, with the former clade represented by at least nine taxa. This high level of diversity can be attributed to the relatively random nature of natural trap cave deposition, reducing accumulation biases due to size or diet. We also record the first occurrence of Merriam’s Shrew (Sorex merriami) from the Bear River Range. Our analysis does not indicate any mammalian changes between late Holocene and present-day communities, but these data establish a new zoological baseline for an alpine community at the interface between two key biogeographic provinces in western North America. Our work highlights the value of collecting skeletal remains from cave assemblages as a convenient and fast method for censusing terrestrial mammalian communities.

中文翻译：

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高山洞穴化石组合在动物普查中的效用：以美国犹他州北部为例

哺乳动物骨骼遗骸的组合为野生动物种群普查提供了强大的工具，以建立评估不同时间尺度的生物地理趋势所需的动物学基线。尽管存在潜在的时间平均和埋藏过滤，但洞穴提供了理想的沉积环境来保存这些骨骼遗骸。我们描述了美国犹他州北部卡什县熊河山脉 Boomerang 洞穴的全新世古生物组合，海拔 2,231 m，位于大盆地和落基山生物地理省之间的边界。我们分析了来自洞穴内六个区域的 1,228 个地表采集的标本，并确定了至少 22 个不重叠的哺乳动物类群，包括该地区存在的所有体型类别。与来自熊河山脉的哺乳动物以及在洞穴附近被困或观察到的个体的博物馆记录相比，基于标本的稀疏表明我们的组合捕获了该地区预期的大部分哺乳动物多样性。这对于食肉动物和体形动物来说尤其明显，它们在回旋镖洞穴组合中特别明显，前一个分支由至少九个类群代表。这种高水平的多样性可归因于天然陷阱洞穴沉积的相对随机性，减少了由于大小或饮食引起的积累偏差。我们还记录了熊河山脉中梅里亚姆鼩鼱 (Sorex merriami) 的首次出现。我们的分析并未表明全新世晚期和当今群落之间存在任何哺乳动物变化，但这些数据为北美西部两个关键生物地理省份之间交界处的高山群落建立了新的动物学基线。我们的工作强调了从洞穴组合中收集骨骼遗骸的价值，作为普查陆地哺乳动物群落的一种方便快捷的方法。