[1] Nectomys squamipes, or the South American water rat can be distinguished from other Sigmodontinae based on their size and morphology of their hindfeet.

They are the largest of the family (average of 216g) and have long hind legs with partially webbed feet to aid in swimming and have completely scaled heels.

N. squamipes have a larger skull that occupies well-developed supraorbital ridges and lambdoidal crests, giving the mammal great attachments for jaw muscles and a strong bite.

They tend to prefer the moist habitats in forested areas such as swamps or marshes, and are sometimes found inhabiting caves The South American water rat has mainly one predator, the barn owl (Tyto alba).

The South American water rat tends to feed more often after the end of the wet season, when food is in abundance.

The South American water rat is a polygynous mammal in which males will increase their home range in attempt to mate with many females to produce the most offspring possible.

Gestation periods last around 30 days and young have an average body length between 10-11 grams, with litters as small as 1 offspring and as large as 7.