Fisheries, Wildlife, and Conservation Biology Program, North Carolina State University, Raleigh, NC, United States of America.
North Carolina Museum of Natural Sciences, Raleigh, NC, United States of America.
PLoS One. 2023 Oct 24;18(10):e0293328. doi: 10.1371/journal.pone.0293328. eCollection 2023.
Ungulate neonates-individuals less than four weeks old-typically experience the greatest predation rates, and variation in their survival can influence ungulate population dynamics. Typical methods to measure neonate survival involve capture and radio-tracking of adults and neonates to discover mortality events. This type of fieldwork is invasive and expensive, can bias results if it leads to neonate abandonment, and may still have high uncertainty about the predator species involved. Here we explore the potential for a non-invasive approach to estimate an index for neonate survival using camera traps paired with decoys that mimic white-tailed deer (Odocoileus virginianus) neonates in the first month of life. We monitored sites with camera traps for two weeks before and after the placement of the neonate decoy and urine scent lure. Predator response to the decoy was classified into three categories: did not approach, approached within 2.5 m but did not touch the decoy, or physically touched the decoy; when conducting survival analyses, we considered these second two categories as dead neonates. The majority (76.3%) of the predators approached the decoy, with 51.1% initiating physical contact. Decoy probability of survival was 0.31 (95% CI = 0.22, 0.35) for a 30-day period. Decoys within the geographic range of American black bear (Ursus americanus) were primarily (75%) attacked by bears. Overall, neonate survival probability decreased as predator abundance increased. The camera-decoy protocol required about ½ the effort and 1/3 the budget of traditional capture-track approaches. We conclude that the camera-decoy approach is a cost-effective method to estimate a neonate survival probability index based on depredation probability and identify which predators are most important.
有蹄类幼崽——指年龄小于四周的个体——通常经历着最高的捕食率，其存活率的变化会影响有蹄类动物的种群动态。典型的测量幼崽存活率的方法包括对成年个体和幼崽进行捕捉和无线电追踪，以发现死亡事件。这种野外工作具有侵入性且昂贵，如果导致幼崽被遗弃，可能会导致结果出现偏差，并且对于涉及的捕食者物种，仍然存在高度不确定性。在这里，我们探索了一种非侵入性方法的潜力，该方法使用相机陷阱和诱饵来估计头一个月生命中白尾鹿（Odocoileus virginianus）幼崽的生存指数。我们在放置幼崽诱饵和尿液气味引诱剂之前和之后的两周内，用相机陷阱监测地点。将捕食者对诱饵的反应分为三类：未接近、在 2.5 米内接近但未接触诱饵、或实际接触诱饵；在进行生存分析时，我们将后两类视为死亡的幼崽。大多数（76.3%）的捕食者接近了诱饵，其中 51.1%的捕食者开始进行身体接触。在 30 天的时间内，诱饵的存活概率为 0.31（95%置信区间为 0.22，0.35）。在美洲黑熊（Ursus americanus）的地理范围内，诱饵主要（75%）被熊攻击。总体而言，随着捕食者数量的增加，幼崽的存活率下降。相机诱饵方案所需的工作量约为传统捕捉追踪方法的一半，预算则为三分之一。我们得出的结论是，相机诱饵方法是一种基于捕食概率来估计幼崽存活率指数的具有成本效益的方法，并可以确定哪些捕食者最重要。
