Neotropical river otter (Lontra longicaudis) identification sheet.


By  Dr. Juan-Pablo Gallo-Reynoso



English: River otter

French: Loutre

Spanish: Perro de agua, Nutria de río, Lobito de río, Nutria

Portuguese: Lontra

German: Flussotter

Italian: Lontra neotropicale di fiume

Nahuatl: Ahuizotl



In Latin-America, from northern México to central Argentina


Conservation status:

Listed in Appendix I of CITES and considered “data deficient” by IUCN.

Protected in Mexico by NOM-059-ECOL-1994 and Ley de Vida Silvestre (Wildlife Law) of Secretaría del

Medio Ambiente y Recursos Naturales.





 © Juan Pablo Gallo                                                              © Juan Pablo Gallo

Adult female showing lateral shape of the head, tail, fore and hind feet and typical coloration.


Adult male showing nose pad (rhinarium) and strong claws.






Typical identification marks

Fur dark brown to pale brown dorsally. The venter is much paler. Throat and lip area are a much paler brown, sometimes yellowish. Some animals show individual white, paler or dark brown, sometimes yellow marks in the throat, chin and lips area.

Webs between all five toes at all four feet. Strong claws in all feet. The sole is devoid of any hair.

Tail is dark brown, very long and flattened. Upper line of the (black and hairless) rhinarium forms the shape of a crown.


Neotropical river otter pup.

                                                    © Juan Pablo Gallo






Rhinarium comparison:


Lontra canadensis                 Lontra longicaudis annectens

                                                                                  © Juan Pablo Gallo








Close view of the head showing the rhinarium, lip and chin yellowish -cream  to pale brown coloration and spotting of the same coloration on the throat.


Female from Chiapas, México. Miguel Álvarez del Toro Zoo. Tuxtla Gutiérrez, Chiapas.


                                               © Fulvio Eccardi


Swimming neotropical river otter, note the length of the tail, which is a noticeable characteristic of the species.


                                                                © Juan Pablo Gallo



Body measurements from neotropical river otters

Sex (n)

Body length (cm)

Tail length (cm)

Total length (cm)

Weight (kg)

Male (3)

83 - 97

55 - 65

138 - 162

16.3 - 24

Female (3)

65 - 76

44 - 51

109 - 127

12.5 - 15



The coloration of the lips and spotting of the chin and spotting of the throat (yellowish-cream  to pale brown) can be seen even when the otter is wet.


                                                               © Juan Pablo Gallo




Food composition of Neotropical river otter is very variable seasonally and geographically. Fishes and crustaceans are the most frequent items. The next table summarizes the preferences in some study areas (approximated).











Species (n)

Occurrences %























Neotropical river otter female from Chiapas, México..

                                                                                                                                             © Juan Pablo Gallo




Sprainting sites are placed on the banks of rivers, lakes and dams, usually over big boulders, rocks, rocky and sandy islands, large roots, branches over the water and felled trees. A place widely used for sprainting is usually called latrine.

 Spraints are also deposited in muddy areas when there is a lot of grasses. Sprainting sites may be found mainly where two rivers come together, separate or change direction and flow, and in the foundation of bridges and other man made objects.

Fresh scats are of soft consistence, with visible contents, mainly fish scales, crustacean exoskeletons and bone fragments of fishes, amphibians, reptiles, birds and mammals, and sometimes with parts of vegetation and fruits.

Color is black to dark brown, pale brown when is composed mainly by fish remains. Old scats composed by crustaceans and fish remains become gray to white.

Scats have a characteristic smell like “musk”.



Spraints deposited on a rock in the river bank.

                                                       © Juan Pablo Gallo










Tracks (original sizes) measurements



Hind foot length (cm)

Hind foot width (cm)

Forefoot length (cm)

Forefoot width (cm)


7.5 – 8.2

7.5 – 8.5

7.0 – 7.5

6.5 - 7.5


6.5 – 7.0

6.5 – 7.0

6.5 – 7.0

6.5 – 7.0


Stride trotting 20 – 30 cm


Forefoot track 7.0 – 7.5 cm


Hind foot track 7.5 – 7.5 cm






Foot prints may vary in size and shape according to the substrate. For example in thick sandy beaches or mud foot prints may measure up to 10 to 12 cm long, and in hard surfaces can be very small, 4 – 5 cm long. The stride while trotting is about 20 – 30 cm overlapping hind foot on forefoot.

 Foot prints may also vary depending on the age and sex of the individual.


                                                                       © Juan Pablo Gallo





A typical den of neotropical river otter. Dens usually have two entrances, one from land and another from the water. They are usually found were large boulders form caves, holes on trees and roots, holes on the ground or dens usually excavated by another animal, mud mounts and inside tall grasses in the river banks.



                                                                       © Juan Pablo Gallo




Aranda, J. M. 1981. Rastros de los mamíferos silvestres de México. Manual de campo. Instituto Nacional de Investigaciones sobre Recursos Bióticos, Xalapa. Veracruz. 198 p.


Gallo-Reynoso J. P. 1989. Distribución y estado actual de la nutria o perro de agua (Lutra longicaudis annectens Major, 1897) en la Sierra Madre del Sur, México. Tesis de Maestría, Facultad de Ciencias. UNAM. 236 p.


All photographs taken by the author with the exception of the close up of a face of a river otter taken by Fulvio Eccardi. Rhinarium drawings were done by the author. Foot print drawings were taken from Aranda (1981).
















Conditions of use: The contents of this page (photographs, drawings and text) can be used for educational purposes, giving the appropriate citation; please notify the author. They can not be used for commercial purposes without the written permission by the author.


Citation example:


Gallo-Reynoso, J. P. 2002. Neotropical river otter (Lontra longicaudis) identification sheet.

     Grupo de Conservación de las nutrias en México. CIAD-Guaymas.














Design and elaboration: © Juan Pablo Gallo Reynoso

Page created January 15, 2002.

Comments on this page, send to:

Dr. Juan Pablo Gallo Reynoso

Centro de Investigación en Alimentación y Desarrollo, A.C.

Unidad Guaymas

Carretera a Varadero Nacional Km 6.6

Colonia Las Playitas

Guaymas, Sonora

C. P. 85480



Cuadro de texto: Grupo de conservación de las nutrias en México