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Adaptive Foraging and Anti-Predator Effort: Impact on Self-Extinction Risk in Timid Consumers

This study explores how adaptive changes in foraging and anti-predator behavior can lead to self-extinction in timid consumers. The research delves into the dynamics of frequency-dependent selection, population growth rates, and predator-prey interactions, highlighting the trade-offs between antipredator effort and foraging time. The model presented in the study analyzes the fitness of herbivores in different scenarios and considers the equilibrium population levels, evolutionary dynamics, and exploitation of predator-prey systems. The findings suggest that fishing effort and feedback control mechanisms can influence stock collapses, emphasizing the need to incorporate evolutionary responses in endangered species management. Ultimately, the study questions whether evolutionary responses consistently lead to population size increases, illustrating how fishing pressure can impact foraging behavior and potentially contribute to species extinction.

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Adaptive Foraging and Anti-Predator Effort: Impact on Self-Extinction Risk in Timid Consumers

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  1. Self-extinction due to adaptive change in foraging and anti-predator effort • Matsuda H, Abrams PA (1994a) Runaway evolution to self-extinction under asymmetric competition. Evolution 48:1764-1772. • Matsuda H, Abrams PA (1994b) Timid consumers: self-extinction due to adaptive change in foraging and anti-predator effort. Theor Pop Biol 45:76-91. • Matsuda H, Abrams PA (2004) Effects of predator-prey interactions and adaptive change on sustainable yield. Can J Fish Aq Sci in press

  2. Matsuda & Abrams (1994a, b) • Frequency dependent selection may decrease the population size and the population growth rate. • Therefore, self-extinction due to frequency-dependent selection is possible. • e.g., Timid herbivores (Matsuda & Abrams 1994, Theor. Pop. Biol. )

  3. Tradeoff between antipredator effort and foraging time benthos (constant density R) plant (constant density R) flatfish (change in trait Ĉ & population size N) herbivore (change in trait Ĉ & population size N) fishery (constant density P) carnivore (constant density P)

  4. Model I: Harbivore’s fitness W • W(C) = B(CR) - M(C,P) - d • Optimal foraging time • always decreases as predator increases;

  5. Optimal foraging time • I = ĈR: Foraging intake rate I= (individual’s foraging time)(plant density), • B = ĈR/(1 + bĈR)Benefit B from intake saturates with intake, • Risk M of predation (type II functional response)M = ĈP / (1 + hCN) • C is population mean trait valueh: handling time

  6. Population & evolutionary dynamics • Equilibrium population • N* = Ns (stable level) • N* = Nu (unstable critical level) • N* = 0 (extinct)

  7. figures ESS ESS ESS ESS

  8. A model for exploitation of predator R: prey density; N: consumer density; e1: fishing effort; C: foraging time; q: catchability; V; evolution velocity;

  9. Non-standard fisheries-stock/yield relationship fishing effort may increase stock. Stock△ and yield○ are maximized just before stock collapse. P Stock & yield Y Fishing effort

  10. Feedback control may result in stock collapse. S Target CPUE

  11. Feedback control may result in stock collapse.

  12. We should take account of adaptation in managing endangered species. • Does evolutionary response of species always increase its population size? • No • “the fish may become poorer foragers as the result of fishing, and that this may result in extinction, or at least contribute to reducing their population size.” (Matsuda & Abrams 1994b)

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