A 2022 report describes orange-brown fur on the forehead, crown, and temples of L. f. fuscicollis. The tamarins were observed north of the Río Abujao in Peru, in terra firme forest that is not seasonally flooded.
In observations made in Peru in 2015 and 2018, L. f. fuscicollis had orange-brown fur on the forehead, crown, and temples.
The paper reports nine sightings during inventories in 2015 and 2018: eight at San Mateo and one at Nuevo Libertad. All sightings were in terra firme forest, which is not seasonally flooded.
An extinction-risk assessment has not been added yet.