First description of the breeding nest of Irenomys tarsalis, a sigmodontine rodent endemic to southern Andean forests

The Chilean tree rat, Irenomys tarsalis, is a sigmodontine rodent endemic to the southern Andean forests. Very little is known about its habits. The aim of this work was to describe its breeding nest. A nest was located inside the hollow of a living Lenga Beech (Nothofagus pumilio) near Fontana Lake, Chubut province, Argentina. The nest was located 2 m above ground and inside an oval hollow, with 2 openings in the upper part and opposite to the main cavity entrance. The nest was built with a few feathers and lichens, dry and fine grass, pieces of small sticks, and scraped material from the internal side of the trunk. Two specimens of flea from the Rhopalopsyllidae family were recovered from the nest. This note allowed us to add new information on the breeding biology of one of the least known sigmodontines of the southern temperate rain forest and to the limited knowledge of sigmodontine rodents.