Predation risks suppress lifetime fitness in a wild mammal

Abstract

Prey often reduce predation risk at the cost of lower resource intake. The cumulative effects of such tradeoffs can alter resource allocation, demography and evolutionary processes. We show how the accumulation of risk effects reduces the growth rate of wild North American porcupines Erethizon dorsatum, and simulate three evolutionary responses related to lifetime reproductive success. Individual porcupines experiencing predation risk from fishers Pekania pennanti grew slower and gave birth to fewer offspring. Simulations show that predation risk alone can lead to population declines, and that a female can replace herself by investing more energy into reproduction or adult survival; females that only invest energy in juvenile survival cannot. We show that the accumulation of predation risk can reduce lifetime reproductive success in natural ecosystems. Estimating the contribution of predation risk, and how evolutionary responses can mediate consequences associated with predation risk, is necessary to understand the evolution of predator–prey systems.

Predator Environment Does Not Predict Life History in the Morphologically Constrained Fish Alfaro cultratus (Cyprinodontiformes: Poeciliidae)

“…Predator environments have often been used to study the effects of mortality rate on life history strategies (Law, 1979;Reznick and Endler, 1982;Johnson and Belk, 1999;Gosline and Rodd, 2008) and have been found to affect a wide variety of taxa, including fish, anurans, and insects. Among other things, the presence of a predator can influence timing and size of maturation and changes among developmental stages (Chivers et al, 2001;Johnson, 2001;Hilton et al, 2002;Stoks et al, 2006;Peterson et al, 2019), growth rate (Lardner, 2000;Altwegg, 2002;Šupina et al, 2016;Brown et al, 2018;DeWitt et al, 2019), and investment in offspring (Johnson and Belk, 2001;Gorini-Pacheco et al, 2017). Previous work consistently finds divergent life history patterns in high-predation and lowpredation environments.…”

Danger, risk and anti‐predator behavior in the life history of long‐distance migratory sandpipers

“…The total impact of predation on a prey population is the sum of the direct predation mortality and the risk effects generated by anti‐predator defenses. For the porcupines studied by DeWitt et al (2019), the risk effects are (measured as the impact on expected lifetime reproductive success) approximately 2.3 times larger than direct killing, a magnitude typical of many other studies (reviewed by Priesser et al 2005).…”

“…Defenses have the benefit of lowering the realized risk, but in setting the appropriate levels their costs must also be considered (Lind and Cresswell 2006). For example, porcupines Erethizon dorsatum forage more cautiously in regions where their specialist predator fishers Pekania pennanti are present (DeWitt et al 2019). The caution increases survival, but slows growth, delays maturity and reduces fecundity, each of which lowers the rate of reproduction.…”

Managing animal movement conserves predator–prey dynamics

“…Predator-prey dynamics vary based on landscape characteristics and animal behaviors (Kareiva 1987). There is immense pressure for animals to optimize costs and benefits because of the immediate payoff (Sih 1980) and long-lasting consequences related to reproduction and fitness (DeWitt et al 2019). Managing costs and benefits of movement has wide-reaching effects for terrestrial species, and may be required to maintain vulnerable species and ecosystem function in both human-dominated and natural landscapes (Whittington et al 2011;Tucker et al 2018).…”