Behavioural versus physiological mediation of life history under predation risk

Abstract

Predator-generated variation in prey energy intake remains the dominant explanation of adaptive response to predation risk in prey life history, morphology and physiology across a wide range of taxa. This "behavioural hypothesis" suggest that chemical or visual signals of predation risk reduce prey energy intake leading to a life history characterized by a small size and late age at maturity. However, size-selective predation can induce either smaller size-early age or large size-late age life history. The alternative "physiological hypothesis" suggests that size-selective cues decouple the relationship between energy and life history, acting instead directly on development. Here we use a series of experiments in a fish-daphnid predator-prey system to ask whether size-selective predator cues induce a physiological mediation of development, overshadowing behaviourally based changes in food intake. We found fish chemical cues reduce the net energy intake in Daphnia magna, suggesting a behaviourally mediated reduction in energy. Experimental manipulation of food levels show further that reductions in food lead to later but smaller size at maturity. However, in line with the physiological hypothesis, we show that D. magna matures earlier and at a smaller size when exposed to fish predation cues. Furthermore, our data shows that they do this by increasing their development rate (earlier maturity) for a given growth rate, resulting in a smaller size at maturity. Our data, from a classic size-selective predation system, indicate that predator-induced changes in this system are driven by physiological mediation of development rather than behavioural mediation of energy intake.

Larval crowding leads to unusual reaction norms for size and time at maturity in a geometrid moth (Lepidoptera: Geometridae)

“…This kind of plastic change may be a by-product of anti-predator behaviour (Ball & Baker, 1996) or represent adaptive modifications of growth schedules per se (Beckerman et al, 2007). Within this conceptual framework, the case of E. atomaria can be considered an adaptive modification, as both growth rate and development rate are affected (see also Tammaru et al, 2000, for a related discussion of crowding effects).…”

Life history traits of the invasive estuarine shrimp <i>Palaemon macrodactylus</i> (Caridea: Palaemonidae) in a marine environment (Mar del Plata, Argentina)

“…Predation is another factor commonly recognized as modelling the maximum size and size at maturity of many species (Alon and Stancyk 1982, Reznick and Endler 1982, Beckerman et al 2007) and it could be responsible for the observed differences. However, no information is available about predation pressure on P. macrodactylus at any of the localities.…”

Is Fear a Factor in Voles? Short Term Physiological and Behavioural Response to Predation Stress

“…Our result is more in concordance with a general initial response to a disturbance, which may or may not include predation threat. In terms of metabolism, the general initial response to a disturbance is an increase in oxygen consumption from elevated respiration (Woodley & Peterson 2003, Beckerman et al 2007). Thus, we suggest that in this short-term response, the increase in the vigilance response pays off for any disturbance, threat or benign.…”

“…In addition, induction of stress proteins has been demonstrated under the risk of predation in a variety of species (Kagawa et al 1999 Pauwels et al 2007, Slos & Stocks 2008. As a response to increased need for stress proteins, an increase of energy consumption has also been observed (Woodley & Peterson 2003, Beckerman et al 2007, Slos & Stocks 2008, which in turn could be linked to predator-induced growth reduction (Slos & Stocks 2008).…”