Santamartamys is a nocturnal rodent, and its diet is unknown, but it is assumed to feed on plant matter such as fruits or seeds, like similar species in family Echimyidae. It is able to easily climb a vertical wooden surface. The specimen observed in 2011 made no sounds. It is endemic to Colombia, and has only been found in Sierra Nevada de Santa Marta at altitudes of . Due to the location's isolation and specific geological and climatic conditions, this mountainous region has high levels of biodiversity and endemism. It is believed that the habitat of Santamartamys is suffering degradation.