Do introduced apex predators suppress introduced mesopredators? A multiscale spatiotemporal study of dingoes and feral cats in Australia suggests not

1. The role of apex predators in structuring ecosystems through the suppression of mesopredator activity and abundance is receiving increasing attention, largely due to the potential benefits for biodiversity conservation. In Australia, invasive mesopredators such as feral cats (Felis catus) have been identified as major contributors to Australia’s mass mammal extinctions since European arrival. The introduced dingo (Canis familiaris) has been proposed as a novel way to suppress the impacts of feral cats, however scientific evidence of the dingo’s suppressive role is equivocal. 2. We used camera traps to investigate whether a large introduced predator (dingo) suppresses the activity of an established introduced mesopredator (feral cat) across a national park site conserving endangered species, and an agricultural site supporting cattle grazing enterprises. 3. Feral cats and dingoes exhibited marked overlap in both temporal and spatial activity, indicating coexistence. Some temporal separation was evident at the agricultural site, however this reflected higher diurnal activity by dingoes, not a responsive shift in cat activity. Cat activity times were unrelated to dingo presence and did not differ between areas occupied by dingoes and dingo-free areas. There was no evidence of dingoes excluding cats from patches at either site, nor was there evidence of within-night fine-scale spatiotemporal avoidance of dingoes by cats. 4. Species co-occurrence models revealed dingoes had no negative effect on the probability of cat presence. The probability of detecting a cat on the national park was significantly higher in areas with dingoes than in dingo-free areas, while on agricultural land, cat detectability did not differ between areas with and without dingoes. Cats remained active, abundant and widespread across both sites, with evidence of cats hunting and breeding successfully in areas occupied by dingoes. 5. Synthesis and applications. Our findings indicate that feral cats can coexist with dingoes, without apparent suppression of cat activity, abundance, or fitness. Proposals to reintroduce or restore dingoes and other large predators to suppress invasive mesopredators and conserve biodiversity should be carefully evaluated on a site-by-site basis, as their ability to suppress cats and protect species of conservation significance will likely be context dependent.

1. 顶级捕食者（apex predators）通过抑制中级捕食者（mesopredator）的活动与种群丰度来调控生态系统结构的作用，正受到越来越多的关注，这在很大程度上源于其对生物多样性保护的潜在价值。在澳大利亚，自欧洲殖民者抵达以来，野猫（Felis catus）等入侵性中级捕食者被认定为该国大规模哺乳动物灭绝事件的主要诱因。有学者提出引入澳洲野犬（Canis familiaris）以抑制野猫的危害，但关于澳洲野犬是否具备此类抑制作用的科学证据仍存在争议。
2. 本研究借助红外相机陷阱（camera traps），在一处保护濒危物种的国家公园样地与一处开展肉牛养殖的农业样地中，探究大型入侵捕食者澳洲野犬是否能够抑制已建立种群的入侵性中级捕食者——野猫的活动。
3. 野猫与澳洲野犬的时间活动模式与空间活动范围均存在显著重叠，表明二者可实现共存。在农业样地中虽存在一定的时间分离现象，但这源于澳洲野犬更高的昼行性活动水平，而非野猫活动的响应性偏移。野猫的活动时段与澳洲野犬的存在并无关联，且在有澳洲野犬栖息的区域与无澳洲野犬的区域之间，野猫的活动模式也未出现差异。两处样地均未发现澳洲野犬将野猫排除出特定斑块的证据，也未观察到野猫在夜间细尺度时空上主动回避澳洲野犬的现象。
4. 物种共现模型（species co-occurrence models）结果显示，澳洲野犬对野猫的存在概率并无负面影响。在国家公园样地中，有澳洲野犬栖息区域的野猫检测概率显著高于无澳洲野犬的区域；而在农业用地中，野猫的检测概率在有澳洲野犬与无澳洲野犬的区域间并无显著差异。两处样地中的野猫均保持活跃、种群丰度较高且分布广泛，且有证据表明，野猫在澳洲野犬栖息的区域内仍能成功捕猎与繁殖。
5. 综合与应用。本研究结果表明，野猫可与澳洲野犬实现共存，且未对野猫的活动、种群丰度或适合度（fitness）造成明显抑制。因此，对于通过重新引入或恢复澳洲野犬等大型捕食者来抑制入侵性中级捕食者、进而保护生物多样性的相关提议，应逐样地进行谨慎评估，因为这类捕食者抑制野猫、保护具有保护价值物种的能力，很可能依赖于具体的环境背景。