Designing anti-predator training to maximize learning and efficacy assessments

Despite the growing need to use conservation breeding and translocations in species’ recovery, many attempts to reintroduce animals to the wild fail due to predation post-release. Released animals often lack appropriate behaviours for survival, including anti-predator responses. Anti-predator training—a method for encouraging animals to exhibit wariness and defensive responses to predators—has been used to help address this challenge with varying degrees of success. The efficacy of anti-predator training hinges on animals learning to recognize and respond to predators, but learning is rarely assessed, or interventions miss key experimental controls to document learning. An accurate measure of learning serves as a diagnostic tool for improving training if it otherwise fails to reduce predation. Here we present an experimental framework for designing anti-predator training that incorporates suitable controls to infer predator-specific learning and illustrate their use with the critically endangered Hawaiian crow, ‘alalā (Corvus hawaiiensis). We conducted anti-predator training within a conservation breeding facility to increase anti-predator behaviour towards a natural predator, the Hawaiian hawk, ‘io (Buteo solitaries). In addition to running live-predator training trials, we included two control groups, aimed at determining if responses could otherwise be due to accumulated stress and agitation, or to generalized increases in fear of movement. We found that without these control groups we may have wrongly concluded that predator-specific learning occurred. Additionally, despite generations in human care that can erode anti-predator responses, ‘alalā showed unexpectedly high levels of predatory wariness during baseline assessments. We discuss the implications of a learning-focused approach to training for managing endangered species that require improved behavioural competence for dealing with predatory threats, and the importance of understanding learning mechanisms in diagnosing behavioural problems.

Preparing captive-bred birds for reintroduction: the case of the Vietnam Pheasant Lophura edwardsi

SummaryThe Vietnam Pheasant Lophura edwardsi (including L. hatinhensis) is only known from a small area of central Vietnam, where it occurred in wet forest below 300 m. It is probably extinct in the wild, but some 1,500 birds, derived from 28 individuals caught in 1924–1930, survive in captivity. Guidelines for reintroducing galliforms date from 2009. Subsequent literature was reviewed for new research findings to help maximise the chances of success in reintroducing birds. Studies confirmed that non-parent-reared captive-bred galliforms survive poorly, primarily owing to inadequate anti-predator responses. These reflect both genetic and ontogenetic unsuitability to wild conditions, with progressive maladaptation of stock being related to the number of generations spent in captivity (at least 35 in the case of Vietnam Pheasant). To compensate as far as possible for this deficiency, a reintroduction programme should use: environmental enrichment (including the provision of perches in aviaries), dietary enrichment (especially involving practice with live food), parent-rearing over several generations (although how many are needed for a species almost a century in captivity is unknown), soft releases (allowing full familiarisation with the future environment over at least 50 days), rigorous anti-predator training (against both air and ground attacks), anti-predation release stratagems (relocating and deterring predators, releasing birds at several stations, offering post-release support), determining appropriate numbers (per batch, with at least 300 in total per site) and time-frame for release (around five years) and the selection of fully suitable releasees in (as far as possible) naturally formed social groups, including parent-guided offspring aged around four months. Six sites need survey for extant populations or use for reintroduction, and the choice of reintroduction site will depend primarily on habitat extent and condition. The costs of these measures will be high and the overall project schedule will need to extend beyond the overall five years currently planned.

School is out on noisy reefs: the effect of boat noise on predator learning and survival of juvenile coral reef fishes

Noise produced by anthropogenic activities is increasing in many marine ecosystems. We investigated the effect of playback of boat noise on fish cognition. We focused on noise from small motorboats, since its occurrence can dominate soundscapes in coastal communities, the number of noise-producing vessels is increasing rapidly and their proximity to marine life has the potential to cause deleterious effects. Cognition—or the ability of individuals to learn and remember information—is crucial, given that most species rely on learning to achieve fitness-promoting tasks, such as finding food, choosing mates and recognizing predators. The caveat with cognition is its latent effect: the individual that fails to learn an important piece of information will live normally until the moment where it needs the information to make a fitness-related decision. Such latent effects can easily be overlooked by traditional risk assessment methods. Here, we conducted three experiments to assess the effect of boat noise playbacks on the ability of fish to learn to recognize predation threats, using a common, conserved learning paradigm. We found that fish that were trained to recognize a novel predator while being exposed to ‘reef + boat noise’ playbacks failed to subsequently respond to the predator, while their ‘reef noise’ counterparts responded appropriately. We repeated the training, giving the fish three opportunities to learn three common reef predators, and released the fish in the wild. Those trained in the presence of ‘reef + boat noise’ playbacks survived 40% less than the ‘reef noise’ controls over our 72 h monitoring period, a performance equal to that of predator-naive fish. Our last experiment indicated that these results were likely due to failed learning, as opposed to stress effects from the sound exposure. Neither playbacks nor real boat noise affected survival in the absence of predator training. Our results indicate that boat noise has the potential to cause latent effects on learning long after the stressor has gone.