It is physically similar to the northern (L. canadensis) and southern river otter (L. provocax), which occur directly north and south of this species' range, respectively.

[3] The neotropical otter is found in many different riverine habitats and riparian zones, including those in tropical and temperate deciduous to evergreen forests, savannas, llanos (of Colombia and Venezuela) and the pantanal (in Bolivia, Brazil and Paraguay).

The Neotropical otter has a very wide range, covering a large portion of South America, so it is not surprising there are geographical structures separating some populations.

[6] They possess a long wide tail, with short stout legs and fully webbed toes.

The dental formula (for half the skull) is as follows:[9] The Neotropical otter has the widest distribution of all the Lontra species.

They prefer clear, fast-flowing rivers, and are rarely known to settle in sluggish, silt-laden lowland waters or boggy areas.

[10] They require dense riparian vegetation and abundant den sites but, other than that, the Neotropical otter is very versatile and tolerant to environmental change.

The otters prefer den sites that are solid, high, dry, and in proximity to deep water.

In addition to rivers and streams, they can settle in and exploit some rather formidable habitats, such as wastewater treatment plants, rice paddies, sugar cane plantations, estuaries, deltas, drainage ditches, and sometimes swamps.

[12] Neotropical otters will also venture to the seashore and beaches (maintaining an almost "brackish" lifestyle), hunting marine creatures and playing in the highly saline water.

The otter will also occasionally feed on mollusks and small mammals, as well as birds, large insects and fruits.

During the dry season, when less fish and crustaceans are available, one study found a higher proportion of frogs in otters' diet.

He spent some time in a site with heavy mud, poor substrate for a den, so he may have been on the move to find food.

[21] Dens may have more than one opening, so the otter can easily exit to forage for food while staying safe from predators.

As a last resort, an otter expend energy to excavate a space among vegetation or a river bank, though those homes are less sturdy.

When humans clear forests for agricultural land, the number of available otter habitats plummets.

In caves, where a water sources may leak through the walls and wash away the scent, the resident may mark areas inside their den.

Some areas, like the Pantanal, have high enough productivity such that both otter species can coexist with little or no competition (niche partitioning).

Illegal hunting, habitat destruction through mining and ranching, and water pollution still affect the population of the Neotropical otter.

More data is needed to determine how much overlap exists between the fishermen's desired catch and the otter's diet.

Fishermen may move out of their regular fishing areas, into deeper pools where the otter usually hunts in the absence of people.

[24] Neotropical otters are threatened by habitat degradation associated with: agriculture, soil compaction, pollution, roadways, and runoff.

[20] One male and one female Neotropical otter were captured near Caucasia, Colombia, and taken to Santa Fe Zoological Park in 1994 and 1996, respectively.