Risk-induced neophobia is constrained by ontogeny in juvenile convict cichlids

Abstract

Recent studies have established that variation in background level of risk has profound effects on antipredator phenotypes. Elevated levels of background risk not only change behaviour, but also physiology, morphology and cognitive function. A variety of prey show neophobic predator avoidance when exposed to short-term elevation in risk. Such phenotypically plastic responses allow prey to balance behavioural trade-offs in the face of uncertain risks. Here, we test the hypothesis that ontogeny functions as a constraining factor in the induction of neophobic predator avoidance. In a series of laboratory trials, we exposed convict cichlids, at three different ontogenetic stages (eggs/wrigglers, juveniles and adults), to conditions of elevated (versus low) risk and tested their response to a novel predator odour (rainbow trout, Oncorhynchus mykiss). When cichlids were exposed as eggs and newly hatched ‘wrigglers’ and tested 21 days later, they showed a significant antipredator response to trout odour. When exposed as ∼18 mm juveniles, cichlids showed a significant avoidance when tested 24 h post-exposure, but not 21 days post-exposure. However, when conditioned as ∼50 mm adults, we found no evidence of induced neophobia. Combined, these results suggest that ontogenetic stage may limit phenotypically plastic neophobia.