Data from: Interspecies interference and monitoring duration affect detection rates in chew cards

Pest monitoring methods should provide unbiased accurate estimates of pest densities and locations, while also minimizing time-in-field and costs. Recent pest mammal monitoring studies have found that chew cards are more effective than conventional mammal monitoring methods, but little experimental work has been done to determine optimal experimental duration or quantify the risks of saturation by one species biasing detections of other species. Here, we used chew cards in three sites within Awarua wetland (Southland, New Zealand) to investigate the optimal amount of time required to detect targeted pest species (rats, possums and mice), and to examine the potential of rats and possums to bias detection rates of other species. We found depressed detections of possums and rats where a contraspecific had been detected on a card, which is consistent with previous studies of a similar duration on interspecies interference. This experiment is the first to analyse the rates at which species detections accrue over the course of a survey, and we found rat detections lagged behind possums for the first four nights. We modelled the effect of survey duration and relative rat abundance on the likelihood of further possum detections. Duration and rat abundance interacted, meaning there are trade-offs to be considered with regard to duration: shorter durations may avoid the risk of saturation in areas of high pest density, but risk not sampling sparse or neophobic populations. Our data suggest that chew cards remain one of the most sensitive pest monitoring tools for rats and possums, compared to conventional methods such as tracking tunnels and wax tags. In areas of moderate pest densities, we suggest that a duration of five nights is optimal for detecting pests. However, in areas of high pest density the sensitivity of chew cards may render them unsuitable because of saturation and interspecies interference effects.

害兽监测方法应当提供无偏且精准的害兽种群密度与分布位置估算，同时尽可能压缩野外作业时长与监测成本。近期的害兽哺乳动物监测研究发现，啃咬卡（chew cards）相较于传统害兽监测方法更为高效，但目前鲜有实验研究用于确定最优实验时长，或量化单一物种饱和对其他物种检测结果产生偏差的风险。本研究在新西兰南地大区的阿瓦鲁阿湿地（Awarua wetland）三个监测站点中布设啃咬卡，旨在探究检测目标害兽物种（大鼠、负鼠与小家鼠）所需的最佳时长，并考察大鼠与负鼠是否会对其他物种的检测率造成偏差影响。研究发现，当啃咬卡上已检测到异种个体时，该卡对负鼠与大鼠的检测成功率会出现下降，这与此前同时长区间内的种间干扰研究结论相符。本实验首次针对调查周期内物种检测率的累积速率展开分析，结果显示在前四晚的监测中，大鼠的检测进度滞后于负鼠。我们构建了模型，分析调查时长与大鼠相对丰度对后续负鼠检测概率的影响，结果表明二者存在交互效应，这意味着监测时长的选择存在权衡空间：较短的监测周期可规避高密度害兽区域出现物种饱和的风险，但可能无法充分采样种群稀疏或具有惧新行为的群体。相较于追踪隧道（tracking tunnels）与蜡标签（wax tags）等传统监测方法，本研究数据表明啃咬卡仍是针对大鼠与负鼠的高灵敏度害兽监测工具之一。在害兽种群密度中等的区域，我们建议采用五晚的监测时长作为最优方案。但在害兽种群密度较高的区域，啃咬卡的高灵敏度可能会因物种饱和与种间干扰效应导致其不再适用。