Monitoring ungulates in steep non-forest habitat: a comparison of faecal pellet and helicopter counts

Faecal pellet counts have been widely used to monitor the abundances of introduced ungulates in New Zealand, but ground-based sampling cannot be conducted safely in the steep non-forest habitats that are common in New Zealand's Southern Alps. Helicopter counts may be an effective technique for monitoring ungulates in steep non-forest habitat. We evaluated the relationship between faecal pellet and helicopter counts of ungulates (primarily feral goat <i>Capra hircus</i>) at 12 non-forest sites in the Southern Alps. Within each site we counted the numbers of ungulates from a helicopter on three occasions and the number of intact faecal pellets along 30 transects. Mean observed densities of feral goats derived from helicopter counts ranged from 0.0 to 20.2 km⁻². There was a positive curvilinear (concave down) relationship between faecal pellet and helicopter counts. Compared with faecal pellet counts, helicopter counts were cheaper, could identify ungulate species and provided estimates of absolute density. Helicopter counts are a cost-effective method for monitoring ungulates in the steep non-forest habitats of New Zealand's Southern Alps.

粪便颗粒计数（faecal pellet counts）已被广泛用于监测新西兰引入有蹄类动物（ungulates）的种群丰度，但在新西兰南阿尔卑斯山广泛分布的陡峭非森林生境中，无法安全开展地面采样。直升机计数或许是监测陡峭非森林生境中有蹄类动物的有效手段。我们在南阿尔卑斯山的12处非森林生境点位，评估了有蹄类动物（主要为野化山羊*Capra hircus*）的粪便颗粒计数与直升机计数之间的关联。在每个点位内，我们通过直升机分三次统计有蹄类动物数量，并沿30条样线统计完整粪便颗粒的数量。由直升机计数推导得到的野化山羊平均观测密度范围为0.0至20.2只·km⁻²。粪便颗粒计数与直升机计数之间呈向下凹的正曲线相关关系。相较于粪便颗粒计数，直升机计数成本更低，可识别有蹄类动物物种，且能提供绝对密度的估计值。直升机计数是一种经济高效的方法，可用于监测新西兰南阿尔卑斯山陡峭非森林生境中的有蹄类动物。