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3. Bottle traps produced much lower detection rates than eDNA sampling, but the cost-efficiency of 31 the two methods can be similar because bottle-trapping is cheaper per sample. The relative cost-32 efficiency of the two sampling methods was sensitive to the available survey budget, the costs of 33 eDNA primer/probe development and sample processing, and the number of positive quantitative 34 PCR assays (qPCRs) used to designate a water sample as positive for newt DNA. Environmental 35 DNA sampling was more cost-efficient than bottle-trapping for small-intermediate budgets when 36 primer/probe development and sample processing costs were low, and 1/4 or 2/4 positive qPCRs was 37 used to label a water sample as positive for newt eDNA. However, bottle traps were generally more 38 cost-efficient than eDNA sampling when primer/probe development and sample processing costs 39 were high …