Testing the maintenance of natural responses to survival-relevant calls in the conservation breeding population of a critically endangered corvid (Corvus hawaiiensis)

Abstract

Vocal communication serves an important role in driving many animals social interactions and ultimately their survival. However, both the structure of and responses towards natural vocal behavior can be lost or subject to alteration under human care. Determining if animals in conservation breeding programs exhibit and respond appropriately to species-specific vocalizations is therefore important for ensuring their survival and persistence post-release. We tested whether endangered alal[a] (Corvus hawaiiensis), which are extinct in nature, have retained their natural responses to vocal calls that were previously linked to survival and reproduction in the wild. We conducted our studies on breeding populations derived from a small number of founding alal[a] maintained under human care since their extinction in the wild in 2002. We presented pairs of alal[a] with alarm, territorial intrusion, and two types of control playback calls (a non-threatening territorial maintenance call and a novel heterospecific call). Alal[a] 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 alal[a] exhibit relevant, species-specific behaviors despite generations under human care. They do illustrate, however, that not all individuals respond appropriately, so animals responses to vocal stimuli may be an important factor to consider in determining the release suitability of individuals. Significance StatementEffective communication is crucial to the survival of many animals, but can erode without natural selection. Therefore, testing the flexibility and maintenance of communication and vocal responses in contexts where animals are isolated from conspecifics or from survival consequences, such as in conservation breeding centers, can help determine species susceptibility to communication loss. We used playbacks of survival-related conspecific calls to test if alal[a] (Corvus hawaiiensis), retained species-specific responses to these calls after generations under human care. We found that birds maintained a species-level natural response, however these natural responses were not consistent across individuals, suggesting that some birds may not be well equipped to survive in the wild without additional training or care.