His master thesis dealt with the relationships of five Peromyscus species in the Sandia Mountains in New Mexico, his dissertation with the small tropical insectivorous bat Myotis nigricans.
Na súa tese de doutoramento abordou as relacións das cinco especies de Peromyscus nas montañas de Sandia en Novo México, co pequeno morcego tropical insectívoro Myotis nigricans.