ABSTRACT When the abundance of ship rats (Rattus rattus) is reduced, sympatric house mice (Mus musculus) are released from constraints of food shortage, intimidation or predation. As a result, mice may become either more abundant or more active and detectable. To distinguish between these effects, we monitored mice at eight sites within Pureora Forest Park during periods of rat removal and non-removal, and supplemented food in mouse-specific feeders to half of the sites. We used live-trapping to estimate mouse relative abundance, and tracking tunnels to detect activity. Mouse relative abundance increased when rats were removed, which correlated with increased mouse activity in tracking tunnels. Analysis of mouse capture probability showed that although rat population levels predominantly influenced mouse relative abundance, mouse detectability was also affected at a subtler level. Fluctuations in mouse relative abundance were driven by immigration, and there was evidence that mice were food-limited in the presence of abundant rats. However, this effect was not offset by supplementing food, so it is unlikely that exploitation competition alone limits mice in the presence of rats. Instead, when ship rats were abundant the danger to mice was likely to have limited their foraging opportunities. Evidence of direct predation of mice by ship rats was observed, but it is unclear what role direct predation plays in determining mouse abundance relative to risk effects.

中文翻译：

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Pureora森林公园船鼠和家鼠之间的相互作用

摘要 当船鼠 (Rattus rattus) 的数量减少时，同域家鼠 (Mus musculus) 会从食物短缺、恐吓或捕食的限制中释放出来。结果，小鼠可能变得更丰富或更活跃和可检测。为了区分这些影响，我们在清除和不清除大鼠期间对 Pureora 森林公园内八个地点的小鼠进行了监测，并在一半地点的小鼠特定饲养器中补充了食物。我们使用实时捕获来估计鼠标的相对丰度，并使用跟踪隧道来检测活动。移除大鼠后，小鼠的相对丰度增加，这与小鼠在跟踪隧道中的活动增加有关。小鼠捕获概率分析表明，尽管大鼠种群水平主要影响小鼠的相对丰度，鼠标可检测性也受到更微妙的影响。小鼠相对丰度的波动是由移民驱动的，有证据表明，在大量大鼠存在的情况下，小鼠的食物是有限的。然而，这种影响并没有被补充食物所抵消，因此在有老鼠的情况下，单独的开发竞争不太可能限制老鼠。相反，当船鼠数量众多时，对老鼠的危险可能会限制它们的觅食机会。观察到船鼠直接捕食小鼠的证据，但尚不清楚直接捕食在确定与风险影响相关的小鼠丰度方面发挥什么作用。这种影响并没有被补充食物所抵消，因此在有老鼠的情况下，单独的开发竞争不太可能限制老鼠。相反，当船鼠数量众多时，对老鼠的危险可能会限制它们的觅食机会。观察到船鼠直接捕食小鼠的证据，但尚不清楚直接捕食在确定相对于风险影响的小鼠丰度方面起什么作用。这种影响并没有被补充食物所抵消，因此在有老鼠的情况下，单独的开发竞争不太可能限制老鼠。相反，当船鼠数量众多时，对老鼠的危险可能会限制它们的觅食机会。观察到船鼠直接捕食小鼠的证据，但尚不清楚直接捕食在确定相对于风险影响的小鼠丰度方面起什么作用。