Small mammals of the Holocene sequence of Postes Cave (SW Spain): biogeographic and palaeoenvironmental implications for southwestern Iberia

Postes Cave in SW Spain (Extremadura) displays a Holocene archaeostratigraphic sequence radiocarbon-dated to between c. 8.5–4 cal kyr BP (Mesolithic-Chalcolithic). The sediments collected at two areas within the cave yielded small mammal remains belonging to eleven species of rodents, ‘insectivores’, lagomorphs and chiropterans. This small mammal fossil assemblage is one of the few known to date in the southwest of the Iberian Peninsula. Preliminary taphonomic analysis and previously published data suggest that the remains were accumulated by the predatory activity of Eurasian eagle owls and small to medium-sized carnivores such as red foxes. The palaeoenvironmental and palaeoclimatic reconstructions performed show stable conditions with slight variations during its time span, suggesting an initial scenario of open forested habitats during the Mesolithic and Neolithic which progressively decreased in favour of more open habitats during the Chalcolithic coinciding with human-induced changes of the landscape and with the aridification trend of this period. The presence of Microtus cabrerae and Crocidura suaveolens in the assemblage is noteworthy since they are now extinct in this region. The plausible causes and the processes of these extirpations are discussed.

西班牙西南部埃斯特雷马杜拉 (Extremadura) 地区的波斯特斯洞穴 (Postes Cave) 发育有全新世 (Holocene) 考古地层序列 (archaeostratigraphic sequence)，经放射性碳定年，其年代区间约为距今8.5~4千校准年 (cal kyr BP)，对应中石器时代-铜石并用时代 (Mesolithic-Chalcolithic)。研究人员在洞穴内两处区域采集的沉积物中，出土了隶属于啮齿目 (rodents)、食虫类 (insectivores)、兔形目 (lagomorphs) 与翼手目 (chiropterans) 的11个物种的小型哺乳动物遗骸。该小型哺乳动物化石组合是目前伊比利亚半岛 (Iberian Peninsula) 西南部为数不多的已发现同类化石组合之一。初步埋藏学分析 (taphonomic analysis) 及既往发表的研究数据显示，这批遗骸是由欧亚雕鸮 (Eurasian eagle owls) 与赤狐 (red foxes) 等中小型食肉动物的捕食活动堆积形成的。本次开展的古环境与古气候重建结果表明，该时段内整体环境稳定，仅存在小幅波动：中石器时代与新石器时代 (Neolithic) 初期为开阔林生生境，随后这类生境逐渐缩减，至铜石并用时代转变为更为开阔的生境，这一转变与人类活动引发的景观变化以及该时期的干旱化趋势相契合。化石组合中发现的卡氏田鼠 (Microtus cabrerae) 与白齿麝鼩 (Crocidura suaveolens) 具有重要研究价值，因为这两个物种如今已在该区域区域性灭绝。本文还探讨了此次区域性灭绝的可能成因与过程。