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Open Access Publications from the University of California

Do the Remains Remain? The Fate of Bird Carcasses in a Hawaiian Rainforest that is Fenced for Ungulates and Managed for Rodents using A24 Self-resetting Traps


The introduction of rodents to islands poses a threat to native fauna, which often have no adaptation to defend their offspring or themselves from predation. To combat predation of nests and brooding females, the Kauai Forest Bird Recovery Project (KFBRP) has deployed 425 Goodnature A24 self-resetting rat traps at two field sites where high densities of native forest birds remain. One site is fenced to exclude invasive ungulates. KFBRP conducts routine trap checks every four months to assess bait and trap function and count carcasses. Typically, we find 0-3 rat or mouse carcasses at a trap, but in November 2018, we found a dead bird under a trap at the fenced site. We assume that traps kill more animals than indicated by carcass counts, because 75% of traps have counters that record when traps fire, and counter tallies exceed carcass counts. Thus, we hypothesize that some carcasses are scavenged or decompose between trap checks, and as a result we are a) underestimating target mortality with carcass counts and b) failing to detect non-target mortality. To test our hypotheses, we placed 30 non-native bird carcasses on transects in the fenced trapping grid in early December 2018. Carcasses were surveyed every at 10, 20, 45, 90, and 130 days after deployed. At the end of survey period, 19 (63%) carcasses could be easily detected, suggesting that we are detecting most carcasses after four months unless they are scavenged. Furthermore, our findings suggest that we would detect non-target mortality if it was prevalent.

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