The North American beaver (Castor canadensis) mostly inhabits the United States and Canada. But now this busy and industrious critter is expanding its range in Mexico, even in the urban area of Monterrey. (The Spanish term for beaver is castor.)
Biologist Carlos Galindo Leal wrote an article in Aristegui Noticias, entitled ¿Castores en la zona urbana de Monterrey? (“Beavers in the urban zone of Monterrey?”).
From Galindo’s article (my translation): “The distribution of the North American Beaver is wider than was thought, thanks to Citizen Science. This species of rodent, that can weigh up to almost 40 kilos, is considered an inhabitant of the Rio Bravo (Rio Grande) and adjacent zones in the northeast of Mexico. Nevertheless, the observations of Citizen Science have widened the sightings towards the south… including the urban zone of Monterrey, Nuevo Leon. The unmistakable tracks of their feet with webbing on the toes, and the trees cut with their powerful teeth, indicate [the presence of] this industrious animal…the webbing between the toes of the beaver are easy to recognize. Besides, beavers are untiring dam builders and their traces on cut trees are also easy to identify.”
And the beavers of Monterrey?
“Citizen Science has registered the presence of the North American Beaver in the Santa Catarina River and the La Silla River which cross the great city of Monterrey. Twenty-three observers have contributed to extend the distribution of this rodent mammal through the state of Nuevo Leon. A third of the observations have been recent (2024), but also they have uploaded images since 2009, before the iNaturalistMX website began. [Website located here]. This underscores the importance of retrieving photos and uploading them on the platform [iNaturalistMX], indicating the place and approximate date when they were taken.”
On the other hand, Galindo reports that “In the Cumbres de Monterrey National Park [near Monterrey], with more than 5000 registered species to date, there is only one sighting of beaver traces.”
So, 1 beaver trace sighting in a national park and 23 in urban Monterrey.