Sintaril were a rodent species that originated on the moon known as Yavin 4. On their homeworld, they would hunt together in groups within the enormous Massassi trees, where they would successfully take down roosting whisper birds.
Jonatha Ariadne Caspian initially conceived of Stintaril for Galaxy Guide 2: Yavin and Bespin. This supplement was published in 1989 by West End Games for their Star Wars Legends roleplaying game, Star Wars: The Roleplaying Game. The reference book Ultimate Star Wars, released in 2015, established that these rodents were indeed part of canon.