About the Authors

Fiona M. Underwood

fiona@fmunderwood.com

Affiliations Department of Mathematics and Statistics, University of Reading, Reading, United Kingdom, Independent Consultant, Reading, United Kingdom

Robert W. Burn

Affiliation Independent Consultant, Reading, United Kingdom

Tom Milliken

Affiliation TRAFFIC International, Harare, Zimbabwe

Competing Interests

The authors have declared that they have no competing interest.

Author Contributions

Analyzed the data: FMU RWB. Wrote the paper: FMU RWB TM. Conceived and designed and managed the study: FMU RWB. Database design: RWB. Database management: TM.