Rus Hoelzel is a molecular ecologist who has studies marine mammal populations for over 20 years, including work in the field with various species in North America, South America, Europe, Africa and the South Atlantic. Currently at the University of Durham, he has also worked at Cambridge University, Imperial College and the US National Cancer Institute. He has edited four other books and is editor-in-chief of the journal Conservation Genetics. His research interests include conservation and population genetics, evolution, behavioural ecology and feeding ecology. His work with marine mammals has included studies on vocal behaviour, feeding ecology, reproductive strategy, population genetic structure and the impact of population bottlenecks on genetic diversity.