Abstract

Animals exposed to high levels of predation risk may exhibit a variety of changes in life history, behaviour, physiology and morphology that can affect survival. Under predation threat, prey individuals may increase their aerobic metabolism to allocate energy toward escaping behaviours (e.g. 'fight or flight'), although the associated energetic cost of such behaviour remains largely unknown. Lobsters display different anti-predatory responses, such as sheltering and/or escaping, but the underlying energetic cost of such responses has not been examined. Here, we tested the aerobic metabolic response of southern rock lobsters Jasus edwardsii in the presence of predator (Maori octopus Octopus maorum) olfactory cues (kairomones) using open-flow respirometry. We examined the routine metabolic rate of lobsters in response to predator kairomones during the active phase of their diurnal cycle (at night) to investigate the physiological anti-predator response when lobsters are most vulnerable. Our findings revealed that lobsters strongly reduced their routine metabolism for 3 h by 31.4 % when exposed to kairomones in comparison to controls. Our findings suggest that under laboratory conditions, lobsters exposed to predation risk during the night reduce their activity to avoid predators, i.e. the anti-predator mechanism is to be immobile or inactive rather than showing a fight-or-flight response. Lobster immobility may be an energetically advantageous anti-predator response in the short term; however, prolonged or regular predator exposure could have significant consequences on foraging time and foraging area, with an overall impact on lobster performance, particularly in environments with high predator presence such as fishing grounds.