 Other muroid rodents found at the same places as "T. ucucha" include two akodontines (grass mice), "Akodon latebricola" and "Akodon mollis"; two ichthyomyines (water rats), "Anotomys leander" and "Neusticomys monticolus"; two oryzomyines (rice rats), "Microryzomys altissimus" and "M. minutus"; the thomasomyine "Chilomys instans"; and five other species of "Thomasomys", "T. aureus", "T. baeops", "T. cinnameus", "T. erro", and "T. paramorum".Other species have been recorded nearby, and Voss wrote that "T. ucucha" may occur sympatrically with seven other species of "Thomasomys".With "Akodon latebricola" and "Thomasomys erro", "T. ucucha" is one of three species that are known only from the northeastern Andes of Ecuador.