[1] While at Stanford University, he collected specimens in the Colorado and Mojave Deserts in 1896–1897 before graduating with a degree in zoology in 1901.

[2][3] In 1907, Heller was with Carl Ethan Akeley on the Field Columbian Museum's African expedition.

On his return, he was appointed Curator of Mammals at the Museum of Vertebrate Zoology of the University of California and participated in the 1908 Alexander Alaska Expedition.

[2] At the beginning of the 20th century, Heller led many expeditions to Africa and in 1914 he wrote the book Life-histories of African Game Animals in collaboration with Theodore Roosevelt.

[5] Heller also participated in explorations in Alaska with the Biological Survey, in Peru with Yale University and the National Geographic Society, in China with the American Museum of Natural History, and in Russia with Paul J. Rainey, official photographer to the Czech army in Siberia.