Predation effects on mean time to extinction under demographic stochasticity

TL;DR

This paper models how predation influences the expected time to extinction of prey species under demographic stochasticity, highlighting the importance of interspecific interactions in extinction risk assessments.

Contribution

It introduces a nonlinear functional response model for predation effects on extinction time, emphasizing the impact of foraging parameters independent of equilibrium population size.

Findings

Mean time to extinction varies greatly with foraging parameters.

Exponential dependence of extinction time on handling time.

Interspecific interactions are crucial for accurate extinction risk estimates.

Abstract

Methods for predicting the probability and timing of a species' extinction are typically based on a combination of theoretical models and empirical data, and focus on single species population dynamics. Of course, species also interact with each other, forming more or less complex networks of interactions. Models to assess extinction risk often lack explicit incorporation of these interspecific interactions. We study a birth and death process in which the death rate includes an effect from predation. This predation rate is included via a general nonlinear expression for the functional response of predation to prey density. We investigate the effects of the foraging parameters (e.g. attack rate and handling time) on the mean time to extinction. Mean time to extinction varies by orders of magnitude when we alter the foraging parameters, even when we exclude the effects of these parameters on the equilibrium population size. In particular we observe an exponential dependence of the mean time to extinction on handling time. These findings clearly show that accounting for the nature of interspecific interactions is likely to be critically important when estimating extinction risk.