Data from: Effects of vulture exclusion on carrion consumption by facultative scavengers

Vultures provide an essential ecosystem service through removal of carrion, but globally, many populations are collapsing and several species are threatened with extinction. Widespread declines in vulture populations could increase the availability of carrion to other organisms, but the ways facultative scavengers might respond to this increase have not been thoroughly explored. We aimed to determine whether facultative scavengers increase carrion consumption in the absence of vulture competition and whether they are capable of functionally replacing vultures in the removal of carrion biomass from the landscape. We experimentally excluded 65 rabbit carcasses from vultures during daylight hours and placed an additional 65 carcasses that were accessible to vultures in forested habitat in South Carolina, USA during summer (June–August). We used motion-activated cameras to compare carrion use by facultative scavenging species between the experimental and control carcasses. Scavenging by facultative scavengers did not increase in the absence of competition with vultures. We found no difference in scavenger presence between control carcasses and those from which vultures were excluded. Eighty percent of carcasses from which vultures were excluded were not scavenged by vertebrates, compared to 5% of carcasses that were accessible to vultures. At the end of the 7-day trials, there was a 10.1-fold increase in the number of experimental carcasses that were not fully scavenged compared to controls. Facultative scavengers did not functionally replace vultures during summer in our study. This finding may have been influenced by the time of the year in which the study took place, the duration of the trials, and the spacing of carcass sites. Our results suggest that under the warm and humid conditions of our study, facultative scavengers would not compensate for loss of vultures. Carcasses would persist longer in the environment and consumption of carrion would likely shift from vertebrates to decomposers. Such changes could have substantial implications for disease transmission, nutrient cycling, and ecosystem functioning.

秃鹫（Vultures）通过清除腐肉提供关键生态系统服务，但全球范围内诸多秃鹫种群正急剧衰退，多个物种濒临灭绝。秃鹫种群的广泛衰退可能会提升其他生物可获取的腐肉资源量，但兼性食腐动物（facultative scavengers）对这一资源变化的响应机制尚未得到充分研究。本研究旨在明确，在无秃鹫竞争的前提下，兼性食腐动物是否会提升腐肉取食量，以及它们能否在景观尺度上替代秃鹫完成腐肉生物量清除的生态功能。我们于夏季（6—8月）在美国南卡罗来纳州（South Carolina）的森林生境中开展野外实验：设置65份兔尸样本，在日间阻止秃鹫接触其中的65份；另外设置65份兔尸样本，允许秃鹫自由取食作为对照组。我们借助运动触发式相机，对比实验组与对照组腐肉样本被兼性食腐动物利用的情况。实验结果显示，在无秃鹫竞争的场景下，兼性食腐动物的腐肉取食活动并未出现显著提升。对照组与秃鹫排除组的食腐动物到访频次未表现出显著差异。80%的秃鹫排除组腐肉样本未被脊椎动物取食，而允许秃鹫访问的对照组这一比例仅为5%。在为期7天的实验结束时，未被完全取食的实验组腐肉样本数量较对照组高出10.1倍。本研究表明，夏季条件下，兼性食腐动物无法在功能上替代秃鹫。该研究结果可能受到实验开展时段、实验时长以及腐肉样点间距的影响。我们的研究结果显示，在本研究的温暖湿润环境条件下，兼性食腐动物无法弥补秃鹫种群丧失带来的生态功能空缺。腐肉在环境中的留存时间将更长，腐肉的消耗者也将从脊椎动物转向分解者。此类变化可能对疾病传播、养分循环以及生态系统功能产生深远影响。