Abstract
Habitat degradation is among the top drivers of the loss of global biodiversity. This problem is particularly acute in coral reef system. Here we investigated whether coral degradation influences predator risk assessment and learning for damselfish. When in a live coral environment, Ambon damselfish were able to learn the identity of an unknown predator upon exposure to damselfish alarm cues combined with predator odour and were able to socially transmit this learned recognition to naïve conspecifics. However, in the presence of dead coral water, damselfish failed to learn to recognize the predator through alarm cue conditioning and hence could not transmit the information socially. Unlike alarm cues of Ambon damselfish that appear to be rendered unusable in degraded coral habitats, alarm cues of Nagasaki damselfish remain viable in this same environment. Nagasaki damselfish were able to learn predators through conditioning with alarm cues in degraded habitats and subsequently transmit the information socially to Ambon damselfish. Predator-prey dynamics may be profoundly affected as habitat degradation proceeds; the success of one species that appears to have compromised predation assessment and learning, may find itself reliant on other species that are seemingly unaffected by the same degree of habitat degradation.
Highlights
Our current research focuses on how fish deal with the critical issue of risk assessment within the context of this major habitat change
We predicted that if P. amboinensis did not respond to alarm cues in degraded coral habitats, they should fail to learn the identity of the predator during the training procedure, and not be able to socially transmit this information to naïve observers
The results of our study demonstrate that risk assessment and learning of predators can be dramatically compromised in degraded habitats for fish that most commonly associate with live coral environments
Summary
Our current research focuses on how fish deal with the critical issue of risk assessment within the context of this major habitat change. Whilst the vast majority of prey animals show a somewhat limited ability to recognize predators in the absence of experience[17], there is some evidence that some fish may respond to predator cues without experience[27,28] This includes studies on damselfishes, which have been found to sometimes avoid predator odours at or near the time of settlement[29,30,31]. We tried to teach P. amboinensis the identity of an unknown predator with alarm cues and tested whether they could transmit the information to naïve conspecifics through social learning. We predicted that if P. amboinensis did not respond to alarm cues in degraded coral habitats, they should fail to learn the identity of the predator during the training procedure, and not be able to socially transmit this information to naïve observers. We investigated whether P. amboinensis could compensate for the effect of degraded coral on their risk assessment by learning risk from a close rubble-dwelling heterospecific, the Nagasaki damselfish (Pomacentrus nagasakiensis)
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