Pre-release training, predator interactions and evidence for persistence of anti-predator behavior in reintroduced `alalā, Hawaiian crow

Abstract

Animal translocations commonly fail due to predation after release, especially if animals are reared in human care, away from natural predation pressure. Anti-predator training can be a useful tool for combating the predator naivety of released animals, but its effective implementation requires attention to numerous details. We present the step-by-step development of an anti-predator training regime, tailored to the critically endangered `alalā (Corvus hawaiiensis). `Alalā are the last remaining corvid species of the Hawaiian islands, and historically the level of predation they experienced from the Hawaiian hawk, `io (Buteo solitarius) is unclear. However, one factor thought to compromise outcomes of earlier attempts to reintroduce `alalā in the 1990′s was predation by `io, motivating the development of anti-predator training for recent `alalā releases. We documented evidence for what appears to be competent anti-predator behavior in conservation-bred `alalā, with a range of behavioral strategies for coping with `io observed during a series of controlled presentations of `io and `io-related stimuli. These behavioral responses included vigilance, alarm calling, and mobbing during experimental trials conducted in release training aviaries. Our results did not conclusively establish that anti-predator learning occurred as a result of the training, or that the training produced enhanced survival. However, following release, `io-`alalā encounters were observed on more than 35 occasions, and `alalā responses mirrored those observed pre-release, including the first ever recorded mobbing interactions by juvenile flocks of `alalā in the wild. While it is unclear the extent to which training encouraged these species-appropriate anti-predator responses, their occurrence suggests that the `alalā has retained and can express defensive behavioral strategies. By documenting the design process, training execution and behavioral outcomes in `alalā, we highlight details that other reintroduction programs may need to consider when preparing animals for reintroduction alongside natural predators.