He was better known as Arnaldo de Wilkelried, his name given in honor of the Swiss soldier Arnold von Wilkelried who died at the Battle of Sempach in 1386. In 1887, he emigrated to Paraguay along with his family. He first began studying zoology with his father, the naturalist Moisés Santiago Bertoni in the neighborhood of Guillermo Tell, now called Puerto Bertoni in the Alto Paraná Department of Paraguay, along the Paraná River.