Review of hyperdispersal in wildlife translocations.

Species translocation is a common tool to reverse biodiversity loss, but it has a high failure rate. One factor that contributes to failure is postrelease hyperdispersal, which we define as the long-distance movement of individuals resulting in their failure to contribute to population establishment. We reviewed reported incidences of hyperdispersal and compared rates of hyperdispersal among taxa, population demographics, release cohorts, and success of mitigation techniques. Of 151 conservation translocations (reinforcements and reintroductions) in which animals were tracked, hyperdispersal was confirmed in 52.1% of programs. The prevalence of hyperdispersal (percentage of studies) was relatively consistent across taxa (42.9-60%), but hyperdispersal rates in birds were likely underestimated because 76.9% of bird translocations showed incidences in which birds could not be located after release, but hyperdispersal was unable to be confirmed. Eutherians exhibited a higher average incidence of hyperdispersal (percentage of hyperdispersing individuals in a cohort) of 20.2% than birds, reptiles, and marsupials (10.4%, 15.7%, and 10.3%, respectively). No significant trends were observed for sex, source population, or translocation type, but there were nonsignificant trends for males to hyperdisperse more than females and for higher incidences of hyperdispersal in reinforcements relative to reintroduction programs. Mitigation techniques included temporary confinement, supplementation of resources, and releasing animals in social groups, but only half of studies examining mitigation techniques found them useful. Hyperdispersal incidence was variable within taxa, and we advise against forming translocations strategies based on results from other species. Hyperdispersal is a significant welfare, economic, and conservation issue in translocations, and we suggest definitions, reporting, and experimental strategies to address it.

Revisión de la hiperdispersión en las reubicaciones de fauna Resumen La reubicación de especies se usa muy seguido como herramienta para revertir la pérdida de la biodiversidad a pesar de tener una tasa elevada de fracaso. Un factor que contribuye a este fracaso es la hiperdispersión posterior a la liberación, la cual definimos como el movimiento de larga distancia de los individuos que resulta en su fracaso para contribuir al establecimiento de la población. Revisamos las incidencias reportadas de la hiperdispersión y comparamos las tasas de hiperdispersión entre los taxones, las poblaciones, demografías, grupos de edad liberados y el éxito de las técnicas de mitigación. Confirmamos la hiperdispersión en 52.1% de 151 reubicaciones de conservación (reforzamiento y reintroducciones) en las cuales se rastreó a los animales. La prevalencia de la hiperdispersión (el porcentaje de estudios) tuvo una coherencia relativa en todos los taxones (42.9-60%), aunque probablemente se subestimaron las tasas de hiperdispersión de las aves porque el 76.9% de sus reubicaciones mostraron incidencias en las que no se pudieron ubicar a los individuos después de la liberación, pero tampoco se pudo confirmar la hiperdispersión. Los euterios exhibieron un promedio de incidencia de hiperdispersión (porcentaje de individuos con hiperdispersión dentro de un grupo de edad) del 20.2%, mayor que el de las aves, reptiles y marsupiales (10.4%, 15.7% y 10.3% respectivamente). No observamos tendencias significativas para el sexo, la población original o el tipo de reubicación, aunque sí hubo tendencias no significativas de mayor hiperdispersión en los machos que en las hembras y de mayor incidencia de hiperdispersión en los reforzamientos en relación con los programas de reintroducción. Las técnicas de mitigación incluyeron el confinamiento temporal, el suplemento de recursos y la liberación de animales en grupos sociales, pero sólo la mitad de los estudios que examinaban estas técnicas las encontraron útiles. La incidencia de la hiperdispersión varió en cada taxón, por lo que aconsejamos no estructurar las estrategias de reubicación con base en los resultados de otras especies. La hiperdispersión es un tema importante para el bienestar, la conservación y la economía de las reubicaciones y sugerimos estrategias de definición, reporte y experimentación para abordarla.

When aggressiveness could be too risky: linking personality traits and predator response in superb fairy-wrens.

Personality syndromes in animals may have adaptive benefits for survival. For example, while engaging in predator deterrence, reactive individuals tend to prioritise their own survival, while proactive individuals engage in riskier behaviours. Studies linking animal personality measured in captivity with individual fitness or behaviours in the wild are sparse, which is a gap in knowledge this study aims to address. We used playback experiments in superb fairy-wrens (Malurus cyaneus), a common Australian songbird with a cooperative breeding system, to assess whether three personality traits measured during short-term captivity correlated with behavioural responses in the wild to a perceived nest and adult predator, the grey currawong (Strepera versicolor). We used three standard measures of personality in birds: struggle responses to human handling (boldness), exploration during a novel environment test, and aggressiveness during a mirror presentation. Superb fairy-wrens showed a significantly stronger response to the predator playback than to the control (willie wagtail, Rhipidura leucophrys) playback, suggesting that they recognised the predator playback as a threat without any accompanying visual stimulus. Birds that attacked their mirror image during the mirror presentation and those that spent a moderate amount of time close to the mirror responded more strongly to predator playback (by approaching the speaker faster and closer, spending more time near the speaker, and being more likely to alarm call) compared to those with low aggressiveness or those that spent very short or long durations close to the mirror. Neither boldness nor exploration in the novel environment test predicted playback response. Our results align with a growing number of studies across species showing the importance of animal personalities as factors for fitness and survival.