Innate anti-predator behavior in captive-reared Piping Plovers (Charadrius melodus)

Background/Question/Methods

Captive-rearing the abandoned young of endangered species for later release has proven useful for supplementing critically small populations. However, studies have shown decreased survival and fitness rates for captive-reared individuals. Handicaps which may influence post-release fitness include a lack of parental training, increased exposure and tolerance for humans, limited exercise opportunities  drastic changes in environment upon release, no prior exposure to inclement weather, decreased foraging experience, and a lack of exposure to predation. To test for the presence of these handicaps, anti-predator responses to both visual and auditory threats, as well as foraging rates were studied in captive-reared endangered Great Lakes Piping Plovers (Charadrius melodus). Playbacks of predator (Ring-billed Gulls (Larus delawarensis), Merlins (Falco columbarius)) and non-predator vocalizations (American Robin (Turdus migratorius)) were combined with parental alarm calls as well as silhouettes of a Merlin and a square to test for vigilant responses in captive-reared chicks.

Results/Conclusions

Captive-reared piping plovers appear to have unlearned abilities to interpret parental alarm calls as well as differentiate between threatening and non-threatening stimuli, whether auditory or visual. Post-release comparisons of captive-reared birds to wild chicks reveal no differences in vigilance, however captive-reared chicks have lower foraging rates, a competitive disadvantage that may lead to decreased survival. We conclude that captive-reared piping plovers possess innate anti-predator defenses, suggesting that other captivity-induced behavioral differences are more likely responsible for post-release fitness declines.