This newly discovered mammal species has a tail that is longer than its entire body

This tiny creature, identified as Thomasomys otavalo or Otavalo’s Andean mouse, was found near Mojanda, a dormant volcano with a caldera filled with lakes. The site is about a 50-mile trip from Quito, a city situated near the high Andes of northern Ecuador. Although only 5 inches from head to butt, it sports an impressive tail of about 6 inches—longer than the rest of its body combined. The discovery of this rodent with such distinctive proportions adds to the fascinating diversity of Andean wildlife, as scientists continue to explore and identify species adapted to this unique mountainous region.
The findings were written in a study published Nov. 5 in the peer-reviewed journal Vertebrate Zoology. The researchers explained that the specific name “Otavalo”, was chosen to honor the Otavalo culture, which is widely recognized for its musical heritage and skilled weaving and textile commerce. For decades, the Otavalos have represented one of the most distinguished and proud indigenous cultures in South America.

According to the study, the mouse has a coat of “fine, dense, and soft” fur. The fur on its back and sides is described as “dark drab,” while its sides show a more brownish tone. On its stomach, the fur is a lighter gray with a hint of “ground cinnamon,” giving it a distinct color gradient across its body. Researchers further explain that the most distinguishable feature of the new mouse species is its tail, which is longer than the length of the entire body combined. The tail is overall covered with fine hairs and a row of scales with a white tip.

Researchers noted that, in comparison to related species, the Otavalos Andean mouse is slightly larger, with shorter hair on its back. Its tail is also described as “noticeably” long when compared to others within the same genus, setting it apart in physical characteristics. The mouse was found in fewer than 10 locations in Ecuador, making them exclusive to northwestern Ecuador. The new species, Thomasomys otavalo sp. nov., has been identified as endemic to the temperate, high-altitude Andean regions of the montane forest. This unique environment is characterized by trees laden with orchids, ferns, and bromeliads, as reported by researchers. Another species, named Igor’s Andean mouse, was also discovered by the researchers from the similar area. The Igor’s Indean mouse too has a long tail, but this time with brown fur.