Vocal communication serves an important role in driving animals' social interactions and ultimately their survival. However, natural vocal behavior can erode in human care. Determining if animals in conservation breeding programs exhibit and respond appropriately to species-specific vocalizations is therefore important for ensuring their survival post-release. We tested whether endangered 'alala (Corvus hawaiiensis), which are extinct in nature, have retained their natural responses to survival-relevant vocal calls. We conducted our studies on breeding populations derived from a small number of founding 'alala maintained in human care since their extinction in the wild in 2002. We presented pairs of 'alala with alarm, territorial intrusion, and two types of control playback calls (a non-threatening territorial maintenance call and a novel heterospecific call). 'Alala were significantly more likely to approach the speaker following alarm call playback than other call types, and were more likely to respond to territorial intrusion calls with the same aggressive territorial calls. Males were more likely to make these aggressive calls than females, mirroring their roles in territory defense. We also found individual consistency in the level of vocal behavior response across all call types, indicating that some individuals are more vocal than others. These results are encouraging, showing that 'alala exhibit relevant, species-specific behaviors despite generations under human care. It does illustrate, however, that all individuals do not respond uniformly, so vocal response may be an important factor to consider in determining the release suitability of individuals.
Occurrence and variability of tactile interactions between wild American crows and dead conspecifics
