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.

粪便颗粒计数法已被广泛用于监测新西兰外来有蹄类动物的种群丰度，但在新西兰南阿尔卑斯山区常见的陡峭非森林生境中，无法安全开展地面采样工作。直升机计数法或许可作为陡峭非森林生境中有蹄类动物监测的有效手段。本研究在南阿尔卑斯山区的12处非森林生境中，评估了有蹄类动物（主要为野生山羊*Capra hircus*）的粪便颗粒计数与直升机计数之间的关联。在每个研究点位，我们分三次通过直升机统计有蹄类动物的数量，并沿30条样带计数完整粪便颗粒的数量。通过直升机计数得到的野生山羊平均观测密度范围为0.0至20.2只每平方千米。粪便颗粒计数与直升机计数之间呈正相关曲线关系（下凹型）。相较于粪便颗粒计数法，直升机计数法成本更低，可识别有蹄类动物种类，并能提供绝对密度的估算值。直升机计数法是新西兰南阿尔卑斯山区陡峭非森林生境中开展有蹄类动物监测的高效经济手段。