The wandering oldfield mouse (Thomasomys erro), also called the "wandering Thomasomys", is a species of rodent

Rodent

Rodentia is an order of mammals also known as rodents, characterised by two continuously growing incisors in the upper and lower jaws which must be kept short by gnawing....

 in the family Cricetidae

Cricetidae

The Cricetidae are a family of rodents in the large and complex superfamily Muroidea. It includes true hamsters, voles, lemmings, and New World rats and mice...

. It has been found in both the Cordillera Oriental

Cordillera Oriental

Cordillera Oriental from the Spanish language meaning "Eastern range" may refer to:* Cordillera Oriental * Cordillera Oriental * Cordillera Oriental * Cordillera Oriental -See also:...

 and Cordillera Occidental of the Andes

Andes

The Andes is the world's longest continental mountain range. It is a continual range of highlands along the western coast of South America. This range is about long, about to wide , and of an average height of about .Along its length, the Andes is split into several ranges, which are separated...

 in central and north central Ecuador

Ecuador

Ecuador , officially the Republic of Ecuador is a representative democratic republic in South America, bordered by Colombia on the north, Peru on the east and south, and by the Pacific Ocean to the west. It is one of only two countries in South America, along with Chile, that do not have a border...

, at elevations from 2400 to 3600 m. It has terrestrial habits, and has been found in cloud forest

Cloud forest

A cloud forest, also called a fog forest, is a generally tropical or subtropical evergreen montane moist forest characterized by a persistent, frequent or seasonal low-level cloud cover, usually at the canopy level. Cloud forests often exhibit an abundance of mosses covering the ground and...

 and areas of secondary vegetation

Secondary forest

A secondary forest is a forest or woodland area which has re-grown after a major disturbance such as fire, insect infestation, timber harvest or windthrow, until a long enough period has passed so that the effects of the disturbance are no longer evident...

. It was formerly considered a subspecies of T. cinereiventer.