He supported scientific investigations in the viceroyalty. In July 1801 he received, with great interest and esteem, the naturalists Baron Alexander von Humboldt, German, and Aimé Bonpland, French, who were traveling with the permission of the Spanish Crown to study the flora, fauna and geography of its American possessions. They also intended to produce a map of South America north of the Amazon River. A map of the viceroyalty was a preoccupation of Mendinueta, who believed that many of the works he wanted to undertake were not possible without a more accurate knowledge of the geography of the colony.