The neotropical otter is very similar-looking to the northern and southern river otter, which sandwich this species' range. Overall length can range from 90–150 centimetres (35–59 in), of which about a third of the length is comprised by the tail. The body weight can range from 5–15 kilograms (11–33 lb).
This otter is found in many different riverine habitats, including deciduous and evergreen forests, savannas, llanos and pantanal. This species likely prefers to live in clear, fast-flowing rivers and streams, and is probably rare in sluggish, silt-laden lowland rivers. It is a solitary animal and feeds on fish and crustaceans. It is an endangered species, according to CITES Appendix I.
^ abWaldemarin, H.F. & Alvares, R. (2008). Lontra longicaudis. In: IUCN 2008. IUCN Red List of Threatened Species. Retrieved 21 March 2009. Database entry includes a brief justification of why this species is of data deficient