Laboratorio Ecotono, INIBIOMA-CONICET, Universidad Nacional del Comahue, Black River, Argentina.
Department of Biogeography and Global Change (BGC-MNCN-CSIC), National Museum of Natural Sciences, CSIC, Madrid, Spain.
PLoS One. 2022 Aug 15;17(8):e0260419. doi: 10.1371/journal.pone.0260419. eCollection 2022.
Foraging decisions by rodents are key for the long-term maintenance of oak populations in which avian seed dispersers are absent or inefficient. Decisions are determined by the environmental setting in which acorn-rodent encounters occur. In particular, seed value, competition and predation risks have been found to modify rodent foraging decisions in forest and human-modified habitats. Nonetheless, there is little information about their joint effects on rodent behavior, and hence, local acorn dispersal (or predation). In this work, we manipulate and model the mouse-oak interaction in a Spanish dehesa, an anthropogenic savanna system in which nearby areas can show contrasting levels of ungulate densities and antipredatory cover. First, we conducted a large-scale cafeteria field experiment, where we modified ungulate presence and predation risk, and followed mouse foraging decisions under contrasting levels of moonlight and acorn availability. Then, we estimated the net effects of competition and risk by means of a transition probability model that simulated mouse foraging decisions. Our results show that mice are able to adapt their foraging decisions to the environmental context, affecting initial fates of handled acorns. Under high predation risks mice foraged opportunistically carrying away large and small seeds, whereas under safe conditions large acorns tended to be predated in situ. In addition, in the presence of ungulates lack of antipredatory cover around trees reduced mice activity outside tree canopies, and hence, large acorns had a higher probability of survival. Overall, our results point out that inter-specific interactions preventing efficient foraging by scatter-hoarders can reduce acorn predation. This suggests that the maintenance of the full set of seed consumers as well as top predators in dehesas may be key for promoting local dispersal.
啮齿动物的觅食决策对于长期维持没有鸟类种子传播者或传播效率低下的栎属种群至关重要。这些决策是由橡子-啮齿动物相遇发生的环境背景决定的。特别是，种子价值、竞争和捕食风险已被发现可以改变森林和人为改造栖息地中啮齿动物的觅食决策。尽管如此，关于它们对啮齿动物行为的联合影响的信息很少，因此，当地的橡子传播（或捕食）也很少。在这项工作中，我们在西班牙的旱生灌丛中操纵和模拟了老鼠-栎属的相互作用，这是一种人为的热带稀树草原系统，附近的区域可能显示出不同的有蹄类动物密度和反捕食者覆盖水平。首先，我们进行了大规模的自助餐厅野外实验，在该实验中，我们改变了有蹄类动物的存在和捕食风险，并在不同的月光和橡子可获得性水平下观察老鼠的觅食决策。然后，我们通过模拟老鼠觅食决策的转移概率模型来估计竞争和风险的净效应。我们的结果表明，老鼠能够根据环境背景调整它们的觅食决策，从而影响已处理橡子的初始命运。在高捕食风险下，老鼠会机会主义地觅食，携带大小种子，而在安全条件下，大橡子往往会在原地被捕食。此外，在有蹄类动物存在的情况下，树木周围缺乏反捕食者的遮蔽物会减少老鼠在树冠外的活动，因此大橡子有更高的生存概率。总的来说，我们的研究结果表明，防止散布贮藏者有效觅食的种间相互作用可以减少橡子的捕食。这表明在旱生灌丛中维持完整的种子消费者和顶级捕食者集合可能是促进当地传播的关键。
