Rio Nutrias is archaic sixteenth and seventeenth century Spanish (primarily rural Castilian) for "beavers river".

[6] On August 2, 1776 Francisco Silvestre Vélez de Escalante wrote in his diary, "...we halted in a small plain on the bank of another arroyo which is called Rio de las Nutrias, because, although it is of permanent and running water, apparently during all or most of the year it stands in pools where they say beavers breed.

"[7] In his annotated 1900 translation of the diary of Francisco Garcés, Elliott Coues wrote in a footnote: "In proof of this use of nutrias for beavers I can cite a passage in Escalante's Diario.

Mex.,2d ser., i, 1854, p. 426: "Aqui tienen las nutrias hechos con palizades tales tanques, que representan a primera vista un rio mas que mediano - here have the beavers made with sticks such ponds that they look at first sight like a river larger than usual"; the reference being of course to the damming of the stream by these animals.

[9] It enters Nutrias Canyon in its last couple miles before its confluence with the Rio Chama.