Radiotracking invasive spread: Are common mynas more active and exploratory on the invasion front?

Understanding the drivers of invasive species’ range expansion is key to effective management and successful control. Spatial sorting theory advances that invasive species can spread via a selection-neutral process predicated on differential movement. In addition to morphology and physiology, it has been predicted that variation in exploration and activity among individuals can be crucial to this model because these behaviors enhance movement. We aimed to address the question of whether exploration and activity are associated with invasive spread using the free-ranging invasive common myna (Acridotheres tristis) in Australia, one of the most broadly distributed invasive birds globally. We radio-tracked mynas from invasion-front sites versus long-established sites in New South Wales. We quantified activity using frequent movements in familiar areas and exploration using infrequent long-distance excursive movements, while also accounting for environmental variation. We discovered that mean daily distance travelled was larger in invasion-front than in invasion-source mynas, suggesting front mynas were more active. Invasion front mynas had significantly larger exploratory home ranges, moved greater maximum daily distances, and changed roost more frequently, suggesting front mynas were also more exploratory; the results were maintained when climate was included as a covariate. To our knowledge, this is the first study to show enhanced exploration and activity in free-ranging invasion-front birds. Inter-individual variation in movement-relevant behaviors might be facilitating the ongoing Australian myna range expansion, although habitat effects cannot be fully excluded. These findings point to the potential importance of considering changes in behavior when modelling alien animal invasions and applied conservation actions.