Occurs only on Isla Mocha, a small coastal island in the Valdivian rainforest zone of central Chile. Despite several surveys of the dense subtropical moist lowland forest in which it occurs, the species has not been recorded since 1994. It is thought that the population is now extremely small. Classified as Critically Endangered (CR B1ab(i,ii,iii)+2ab(i,ii,iii)) on the IUCN Red List of Threatened Species.

The main threat is likely to be from habitat loss and degradation. Local people rely heavily on vegetation for their subsistence and as a result have almost totally deforested the lowlands. These areas are now dominated by grasslands. The remaining Valdivian forest is now restricted to the highest elevations and is subject to logging.

No conservation measures are currently in place. Surveys of the few remaining forest fragments in the highlands are needed to ascertain the range and status of the species and inform conservation action planning.

Like its close relative the common degu, the Pacific degu is diurnal, being most active in the early morning and before sunset. Little else is known of this species. The Pacific degu has relatively primitive octodontid features, including long fur and a tail lacking a substantial tuft. The retention of these characters is thought to have occurred as a result of its isolation on the Isla Mocha.