Current Address: Wakayama Research Center of Agriculture, Forestry and Fisheries, Kushimoto, Wakayama, Japan.
Predation risk suppresses the positive feedback between size structure and cannibalism
Article first published online: 13 JUN 2011
© 2011 The Authors. Journal of Animal Ecology © 2011 British Ecological Society
Journal of Animal Ecology
Volume 80, Issue 6, pages 1278–1287, November 2011
How to Cite
Kishida, O., Trussell, G. C., Ohno, A., Kuwano, S., Ikawa, T. and Nishimura, K. (2011), Predation risk suppresses the positive feedback between size structure and cannibalism. Journal of Animal Ecology, 80: 1278–1287. doi: 10.1111/j.1365-2656.2011.01871.x
- Issue published online: 10 OCT 2011
- Article first published online: 13 JUN 2011
- Received 1 December 2010; accepted 9 May 2011 Handling Editor: Volker Rudolf
- dragonfly larvae;
- inducible offense;
- phenotypic plasticity;
- predation risk;
- salamander larvae;
- size structure;
- top-down effects;
- trait-mediated indirect effects;
- trophic polyphenism
1. Cannibalism can play a prominent role in the structuring and dynamics of ecological communities. Previous studies have emphasized the importance of size structure and density of cannibalistic species in shaping short- and long-term cannibalism dynamics, but our understanding of how predators influence cannibalism dynamics is limited. This is despite widespread evidence that many prey species exhibit behavioural and morphological adaptations in response to predation risk.
2. This study examined how the presence and absence of predation risk from larval dragonflies Aeshna nigroflava affected cannibalism dynamics in its prey larval salamanders Hynobius retardatus.
3. We found that feedback dynamics between size structure and cannibalism depended on whether dragonfly predation risk was present. In the absence of dragonfly risk cues, a positive feedback between salamander size structure and cannibalism through time occurred because most of the replicates in this treatment contained at least one salamander larvae having an enlarged gape (i.e. cannibal). In contrast, this feedback and the emergence of cannibalism were rarely observed in the presence of the dragonfly risk cues. Once salamander size divergence occurred, experimental reversals of the presence or absence of dragonfly risk cues did not alter existing cannibalism dynamics as the experiment progressed. Thus, the effects of risk on the mechanisms driving cannibalism dynamics likely operated during the early developmental period of the salamander larvae.
4. The effects of dragonfly predation risk on behavioural aspects of cannibalistic interactions among hatchlings may prohibit the initiation of dynamics between size structure and cannibalism. Our predation trials clearly showed that encounter rates among hatchlings and biting and ingestion rates of prospective prey by prospective cannibals were significantly lower in the presence vs. absence of dragonfly predation risk even though the size asymmetry between cannibals and victims was similar in both risk treatments. These results suggest that dragonfly risk cues first suppress cannibalism among hatchlings and then prevent size variation from increasing through time.
5. We suggest that the positive feedback dynamics between size structure and cannibalism and their modification by predation risk may also operate in other systems to shape the population dynamics of cannibalistic prey species as well as overall community dynamics.