Citation

Elliott KH, Betini GS, Norris DR. Proc. Biol. Sci. 2017; 284(1857): e878.

Affiliation

Department of Integrative Biology, University of Guelph, Guelph, Ontario, Canada N1G 2W1.

Copyright

(Copyright © 2017, Royal Society of London)

DOI

10.1098/rspb.2017.0878

PMID

28659452

Abstract

Allee effects driven by predation can play a strong role in the decline of small populations but are conventionally thought to occur when generalist predators target specific prey (i.e. type II functional response). However, aside from direct consumption, fear of predators could also increase vigilance and reduce time spent foraging as population size decreases, as has been observed in wild mammals living in social groups. To investigate the role of fear on fitness in relation to population density in a species with limited sociality, we exposed varying densities of Drosophila melanogaster to mantid predators either during an experimental breeding season or non-breeding season. The presence of mantids in either season decreased the reproductive performance of individuals but only at low breeding densities, providing evidence for an Allee effect. We then used our experimental results to parametrize a mathematical model to examine the population consequences of fear at low densities. Fear tended to destabilize population dynamics and increase the risk of extinction up to sevenfold. Our study provides unique experimental evidence that the indirect effects of the presence of predators can cause an Allee effect and has important consequences for our understanding of the dynamics of small populations.

© 2017 The Author(s).

Language: en

Keywords

Drosophila melanogaster; Tenodera sinensis; carry-over effects; extinction risk; non-consumptive effects of predators; small populations