Archived dataset.

A primary consideration of abundance studies that use unmarked animals is whether survey counts accurately reflect the population size or if unknown variation in animal movement or detection probability biases counts irrespective of population size. We posited that high repeatability in counts among temporally replicated surveys would indicate that counts are a good index of abundance. We temporally replicated 49 nocturnal spotlight surveys of white-tailed deer (Odocoileus virginianus) up to three times each (n = 128 total samples) to test the repeatability of this commonly used wildlife monitoring technique. Repeatability was high (R = 0.86), suggesting spring spotlight surveys provide a reliable index of deer population size in Iowa, USA. Fourteen percent of the variation among replicated counts was explained by day of year and, to a lesser degree, a vegetation green-up index. Detection probability was high (~0.70) early in the sampling season and declined considerably during the following 6 weeks. Deer abundance was greater at sites with higher percent landcovers of forest and hay/pasture and was lower at sites with higher landcover in crops. Our findings suggest deer managers should sample prior to green-up in the spring to maximize the proportion of the population that is detectable, and that accounting for seasonality on detection estimation is important for reliable abundance estimates if sampling occurs over a range of phenological progression. Finally, we show that temporal replication of surveys is a logistically feasible method to assess the reliability of abundance estimates from study designs that are normally conducted with single visits.针对使用未标记动物的种群丰度研究，核心关切点在于：调查计数能否准确反映种群规模，抑或是动物活动、检测概率的未知变异，会在不依赖种群规模的情况下对计数结果产生偏倚。本研究提出假设：若在时间重复调查中，计数结果具备较高的重复性，则表明该计数可作为丰度的可靠指标。我们针对49组白尾鹿（Odocoileus virginianus）夜间聚光灯调查开展了时间重复采样，每个位点最多重复调查3次，总计获得128份样本（n=128），以此检验这一常用野生动物监测技术的重复性。本次调查的计数重复性较高（R=0.86），表明在美国艾奥瓦州，春季聚光灯调查可作为鹿种群规模的可靠丰度指标。重复计数结果中14%的变异可由调查日期解释，另有较小比例的变异可通过植被返青指数予以说明。采样季初期的动物检测概率较高（约0.70），但在随后的6周内出现了显著下降。白尾鹿的丰度在森林与干草/牧场用地占比更高的位点更高，而在农作物用地占比更高的位点则更低。本研究结果表明，鹿类管理机构应在春季植被返青前开展采样，以最大化可检测种群的占比；若采样覆盖了不同物候进展阶段，则在检测概率估计中纳入季节因素，对于获得可靠的丰度估算结果至关重要。最后，本研究证实，开展时间重复调查是一种在后勤上可行的方法，可用于评估通常仅开展单次访问的研究设计所得到的丰度估算结果的可靠性。