About the Authors
Department of Zoology, University of Cambridge, Cambridge, United Kingdom
The authors have declared that no competing interests exist.
The author(s) have made the following declarations about their contributions: Conceived and designed the experiments: LPG MB. Performed the experiments: LPG. Analyzed the data: LPG. Contributed reagents/materials/analysis tools: LPG SD. Wrote the paper: LPG MB.