Federal sampling guidelines for the endangered American burying beetle, Nicrophorus americanus Olivier, have historically recommended transects of eight baited pitfall traps spaced 20 m. We compared a new above-ground bucket trap sampling method to standard transects in terms of capture rates, time efficiency, trap mortality, disturbance, and sample range. A single bucket trap was set for three consecutive nights at each site (three bucket-nights) rather than a transect of eight traps set for three nights like standard pitfall traps (24 trap-nights). To facilitate comparisons between methods, an appropriate sample effort conversion was determined to convert bucket-nights to trap-nights. Bucket traps were 75% more time efficient than standard transects and were more resistant to disturbances from scavengers. Abundance estimates for N. americanus were significantly different between methods when a bucket-night was treated as equivalent to a trap-night. The most appropriate sample effort conversion was one bucket-night equals eight trap-nights. For both trap types, the probability of recapture was less than 25% for beetles released directly adjacent to traps and dropped below 5% for beetles greater than 300 m from traps. No trap mortalities resulted from either method in this study, but bucket traps were designed to reduce risks from the most common causes of trap mortality (drowning, heat stress, and predation). Bucket traps had rain covers and allowed for drainage, increased ventilation, and excluded some common predators found in standard pitfall traps. We recommend exclusive use of above-ground bucket traps in future surveys for N. americanus due to increased time efficiency, comparability with standard transects, decreased susceptibility to disturbance, larger bait size, and likely decrease in trap mortality.
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Vol. 66 • No. 3