Predator‐recognition training: a conservation strategy to increase postrelease survival of hellbenders in head‐starting programs

Abstract

For species with declining populations, captive rearing with subsequent release into natural habitats ("head-starting") is often used as part of a conservation strategy. One challenge to head-starting programs is that head-started individuals can suffer high rates of postrelease predation. Head-starting programs are currently being established for hellbenders (Cryptobrancus alleganeinsis), large aquatic salamanders that are experiencing population declines throughout much of the species' range. Although hellbenders have innate recognition of many predators, inexperienced juveniles show only weak recognition of introduced trout. We used a classical conditioning protocol to train captive-reared hellbender larvae to show fright responses to the scent of trout. We exposed hellbender larvae to trout-scented water plus a hellbender distress secretion during training trials. In a subsequent test, these larvae responded to trout cues alone with a fright response; control larvae that were trained with the trout scent plus a blank control did not show a fright response to the trout cues. Learning was specific to trout because trained larvae did not respond to water that had been scented by a suckermouth catfish. Although a number of details remain to be addressed concerning standardized procedures, we recommend that head-starting programs for hellbenders include trout-recognition training.

Training for Translocation: Predator Conditioning Induces Behavioral Plasticity and Physiological Changes in Captive Eastern Hellbenders (Cryptobranchus alleganiensis alleganiensis) (Cryptobranchidae, Amphibia)

“…These results substantiate other work that found that amphibians, including hellbenders, have innate behavioral responses to predator kairomones [32,59,60]. Crane and Mathis [11] found that larval hellbenders, 21-25 weeks old, increase their swimming when exposed to trout kairomones, which they interpreted as evidence of escape behavior. Our findings differ from Crane and Mathis [11], likely because we presented live amphibian prey to largemouth bass as food.…”

“…Crane and Mathis [11] found that larval hellbenders, 21-25 weeks old, increase their swimming when exposed to trout kairomones, which they interpreted as evidence of escape behavior. Our findings differ from Crane and Mathis [11], likely because we presented live amphibian prey to largemouth bass as food. Although their study elicited responses using hellbender slime as an alarm cue, they fed their fish a diet of floating trout feed.…”

“…However, this might be attributed to the fact that we did not present salamander alarm cues in combination with the fish kairomones during the exposure trials. Hellbenders can recognize conspecific alarm cues and perceive it as an indicator of elevated risk [11]. Therefore, adding hellbender slime or alarm cues from other salamanders could have exaggerated behavioral responses.…”

“…Animals reared in captivity are often naïve to predators and can lack experience in predator detection and appropriate avoidance responses [11]. Subsequently, captive-reared animals have higher mortality rates than wild or predator-conditioned conspecifics [12].…”

“…Largemouth bass (Micropterus salmoides) live in sympatry with hellbenders in some rivers and are capable of consuming large prey items, such as 1-3 year old hellbenders [31]. Young, captive hellbenders respond to predatory fish kairomones with altered behavior, suggesting that they accurately identify kairomones as stressful stimuli and have innate recognition to predators, such as largemouth bass [11,32]. Translocations into predator-rich environments could exacerbate stress from transport and release and become detrimental to hellbenders; however, there has been no research to identify whether hellbenders have physiological responses to predators.…”