Comparative Analysis of Behavioural Response of Captive-Reared and Wild-Trapped Northern Bobwhites to Simulated Predator Attacks

Abstract

Isolated populations of Northern Bobwhites (Colinus virginianus) have declined causing many landowners to attempt population restoration by releasing captive-reared birds. These attempts have resulted in high mortality rates, which we hypothesised are caused by captive-reared birds exhibiting more naïve predator avoidance behaviour than wild birds. Captive-reared and wild-trapped Northern Bobwhites were subjected to raptorial and terrestrial predator simulations and their responses were recorded on high definition video. We recorded the time to predator detection, time to anti-predator defence, and reaction type for comparative analysis. Captive-reared birds detected simulated predators quicker than wild-trapped birds, but time to mount an anti-predator defence was not different between groups. The response type, however, was different between groups. Captive-reared birds typically flushed when encountering a simulated predator; yet, wild-trapped birds did not flush at all, and typically ran or held when subjected to the simulated predators. We hypothesise that flushing is a naïve anti-predator response that results in revealing of position in the presence of a threat, thereby increasing the individual risk of predation. These results potentially illuminate at least one reason why captive-reared Northern Bobwhite releases have been largely unsuccessful.

Efficacy of acclimating and releasing captive-reared and wild-translocated Northern bobwhites

“…This may have been due to differences in post-release predator avoidance behavior between captive-reared and wild-translocated birds. 32 This behavior discrepancy could also explain why some accipiters prefer captive-reared bobwhites to wild bobwhites when presented with both. 33 Pre-release acclimation increased site fidelity of captive-reared birds, but had no effect for wild-translocated birds, which partially confirms the findings of Lockwood et al, 43 that acclimated Attwater's prairie-chickens dispersed from release sites later than non-acclimated birds.…”

“…While sources of wild birds are limited, captive-reared bobwhite distributors are abundant. Appropriate predator evasion behavior limits survival of captive-reared birds, 32 but wild-translocated birds were not restricted inordinately by predators. Although we experienced high mortality in both captive-reared and wild-translocated birds, we did see slight increases in call counts when monitoring areas where wild birds existed prior to the study.…”

“…This may have been due to differences in post-release predator avoidance behavior between captive-reared and wild-translocated birds. 32 This behavior discrepancy could also explain why some accipiters prefer captive-reared bobwhites to wild bobwhites when presented with both. 33…”

“…[27][28][29][30] Comparative studies of captive-reared and wild bobwhites have shown physical and behavioral differences that may account for higher mortality observed in captive-reared birds. [31][32][33] Stress is also purported to be a major factor contributing to high post-release mortality in both captive-reared and wild-translocated animals. 8,34,35 To reduce stress during population restorations, soft release methods have been used 35,36 ; however, no consensus of a soft release definition exists in the scientific literature.…”

“…27–30 Comparative studies of captive-reared and wild bobwhites have shown physical and behavioral differences that may account for higher mortality observed in captive-reared birds. 31–33…”