Maximising camera trap data: Using attractants to improve detection of elusive species in multi-species surveys

Camera traps are a key tool in ecological studies, and are increasingly being used to understand entire communities. However, robust inferences continue to be hampered by low detection of rare and elusive species. Attractants can be used to increase detection rates, but may also alter behaviour, and little research has evaluated short-term, localized response to the presence of attractants. We conducted three camera trap surveys in Kibale National Park, Uganda, using food baits and scent lures (“attractants”) at each camera station to entice small carnivores to pass in front of camera stations. To examine the interrelationship between scavenging and response to attractants, we also placed camera traps at five food refuse pits. We modelled the effect of attractant and duration of trap placement on the detection probability of small carnivores and selected African golden cat Caracal aurata prey items. We examine transient site response of each species, by comparing our observed likelihood of detection in each 24 h period from 1–7 d following refreshing of attractants to randomly generated capture histories. African civet Civettictis civetta, rusty-spotted genet Genetta maculata, African palm civet Nandinia binotata, and marsh mongoose Atilax paludinosus detection probabilities were highest and Weyns’s red duiker Cephalophus wenysi detection probability was lowest immediately after attractants were placed. Within 24 h after attractant was placed, rusty-spotted genet and African palm civet were more likely to be detected and African golden cat, red duiker, and blue duiker Philantomba monticola were less likely to be detected. Our results suggest that attractants can increase detection of small-bodied species and include some arboreal species in terrestrial camera trap sampling. However, attractants may also alter short-term visitation rates of some species, with potentially cascading effects on others. Community level and intraguild interaction studies should control for the potentially confounding effects of attractants on spatial activity patterns.红外相机陷阱（Camera traps）是生态学研究的关键工具，如今正愈发广泛地被用于解析完整的生物群落。然而，针对稀有且难以观测物种的低检出率，仍持续阻碍着可靠推论的得出。引诱剂虽可用于提升检出率，但同时也可能改变动物行为，且目前鲜有研究评估动物对引诱剂存在的短期、局域性响应。我们在乌干达基巴莱国家公园开展了三次红外相机陷阱调查，在每一个相机站位处投放食物诱饵与气味引诱剂（统称“引诱剂”），以吸引小型食肉动物途经相机拍摄区域。为探究食腐行为与对引诱剂的响应之间的相互关系，我们还在五个食物垃圾坑处布设了红外相机陷阱。我们构建模型，分析了引诱剂与陷阱布设时长对小型食肉动物以及选定的非洲金猫（Caracal aurata）的猎物的检出概率的影响。我们通过对比每次更新引诱剂后1至7天内，每个24小时周期中观测到的物种检出概率与随机生成的捕获历史，以此检验各物种的瞬时位点响应。在引诱剂刚布设完毕时，非洲灵猫（Civettictis civetta）、斑獛（Genetta maculata）、非洲棕榈狸（Nandinia binotata）与沼泽獴（Atilax paludinosus）的检出概率最高，而韦恩斯红麂羚（Cephalophus wenysi）的检出概率最低。在引诱剂布设后的24小时内，斑獛与非洲棕榈狸的检出概率更高，而非洲金猫、红麂羚以及蓝麂羚（Philantomba monticola）的检出概率更低。我们的研究结果表明，引诱剂可提升小型物种的检出率，并能将部分树栖物种纳入地面红外相机陷阱的采样范围。然而，引诱剂同样可能改变部分物种的短期造访频次，进而对其他物种产生潜在的级联效应。群落水平与功能群内互作研究应当控制引诱剂对空间活动模式造成的潜在混淆效应。