Lontra longicaudis is present from Northwestern Mexico, south into South America; it is the most common otter in Mexico and has the widest distribution of the three S. American Lontra species.

The range extends into Uruguay, Paraguay, and across northern Argentina.

Biogeographic Regions: nearctic (Native ); neotropical (Native )

Lontra longicauda generally weighs less than 12 kilograms. Sexually dimorphic in size, the males average 20-25% larger than the females (Lariviere 1999).

L. longicauda is also known as the Neotropical otter. Head and body length can be 360-660 mm, length of the tail 370-840 mm, length of the hind foot 94-144 mm, and length of the ear ranges from 18-22 mm (Lariviere 1999).

Some average measurements of the long, flat skull include: basal length about 96.4 mm, zygomatic breadth 68.1mm, and postorbital breadth averaging 17.9 mm. The head is small and flat, bearing small eyes and short, round ears. The otter's neck is thicker than the head (Lariviere 1999).

The Neotropical otter has short, dense, sleek pelage, which is described as a lustrous grayish-brown. This otter is slightly paler ventrally, especially on the throat. On its face, the upper lip, mandible, and tip of the muzzle are silvery white to yellowish. The muzzle appears broad. The tail is long, wide, and quite thick at the base. It tapers to a point. The legs are short and stout, and the toes on all the otter's feet are webbed (Lariviere 1999).

Females have four nipples on the abdomen. The males have a well-developed baculum with a total length of around 72 mm. It has a small ventral groove, shallow at the proximal end and running deeper at the distal end (Lariviere 1999).

Range mass: 5 to 15 kg.

Range length: 360 to 660 mm.

Other Physical Features: endothermic ; homoiothermic; bilateral symmetry

Sexual Dimorphism: male larger

• Terrestrial
• Freshwater

Lontra longicaudis generally shelters in a self-excavated burrow near permanent lakes or streams. They depend on a water environment with plenty of riparian vegetation (Nowak 1999).

One study looked at the use of shelters by the Neotropical river otter in Brazil, along the Betari River, between August 1993 and December 1994. There were several different types of shelters frequented by the otters. These shelter types include: a cavity among stones, cavity under tree roots, limestone dissolution cavity, cavity in a rocky wall, space among vegetation, and excavated burrows. The most common type of shelter used by the otters in this study was the cavities among stones (35.2%).This type of shelter is not deep and has a broad entrance. It is actually a space among pebbles and rock along the river bank (Pardini and Trajano 1999).

The Neotropical river otter is also known to use caves as shelters, which other otters tend not to do. A few of the caves were used to rear young. It was suggested the caves were generally far from the main river and were protected sites. These are features common to other otter rearing dens (Pardini and Trajano 1999).

It was also noted that otters' scent marking behavior is concentrated in those areas of the home ranges which they frequent more than others, in their activity centers. Along the Betari River, Lontra longicaudis did not concentrate its scent marks around shelters. Apparently, this means the shelters are not necessarily centers of activity for the otters in riverine habitats (Pardini and Trajano 1999).

Aquatic Biomes: lakes and ponds; rivers and streams

The neotropical otter feeds mainly on fish, crustaceans and molluscs. It is also an opportunistic feeder, eating insects, reptiles, birds, and small mammals. It has been suggested that foraging occurs all day, happening more commonly in the middle or late afternoon. Nocturnal activity is rare, but some neotropical otters have become completely nocturnal when their normal activities are disturbed by humans (Lariviere 1999).

L. longicaudis is a graceful swimmer and diver. They are always found in or near the water. Their foraging dives can last from 20-30 seconds. The otter consumes small prey while in the water but will take larger prey to the shore to eat it (Lariviere 1999).

Two separate studies were conduted regarding the feeding habits of the neotropical river otter and the results are described here. One study was conducted at a dam in the "Duas Bocas" Biological Reserve in Brazil, between July 1986 to July 1987. This reserve is covered mainly by the Atlantic Rain Forest. The study was based on otter fecal (spraints) analysis and compared with known species found in the dam. The material collected was resistant to gastric juice, including fish bones, rays, jaws, and teeth of a number of animals, plus crab and insect exoskeletons (Helder and DeAndrade 1997).

The most important food item was fish, which in this study was present in 97.2% of the samples. Also observed were crustaceans, amphibians, mammals, insects, and birds. Crustaceans were the second most commonly encountered food item. The authors indicated that greater abundance and easier capture of fish make them the main food item for the otters (Helder and DeAndrade 1997).

Between August 1993 and September 1994 another study was carried out in an Atlantic forest stream in south-eastern Brazil, the Betari River. Likewise, the author studied undigested remains in the otter's scat. In 93% of the samples fish was found. Aquatic insects and crustaceans were also found frequently (78.9%). The conclusion of this study was that otters are sometimes influenced in their selection of food items according to the availability of prey and its ability to escape (Pardini 1998).

These studies characterize L. longicaudis as a piscivorous mustelid that engages in opportunistic feeding.

There are a number of animals which prey on Neotropical river otters including anacondas, jaguars, caimans, dogs and birds of prey. Humans kill them for meat, fur, or incidentally in fishing operations, as these otters frequently get caught and drown in nets (Lariviere 1999).

Known Predators:

• anacondas (Eunectes murinus)
• Jaguars (Panthera onca)
• caimans (Alligatorinae)
• birds of prey (Falconiformes)
• domestic dogs (Canis lupus familiaris)
• humans (Homo sapiens)

Depending on the otters' locality, it breeds mostly in the spring, but may also breed throughout the year. Following a gestation period of 56 days, one to five young are born, but generally, there is only two or three in the litter. There is an indication of facultative delayed implantation, but it is not known how long the delay may be (Lariviere 1999).

Young are born blind, opening their eyes after 44 days. They are born fully furred. The young leave the den or nest when about 52 days old and spend most of the day playing near the natal den. At about 74 days post birth they start their aquatic activity with their mothers. Males do not provide any parental care.

Breeding interval: Neotropical otters breed once per year.

Breeding season: Some populations breed only in the spring, others throughout the year

Range number of offspring: 1 to 5.

Average number of offspring: 2-3.

Average gestation period: 56 days.

Key Reproductive Features: iteroparous ; seasonal breeding ; year-round breeding ; gonochoric/gonochoristic/dioecious (sexes separate); viviparous ; delayed implantation

Average gestation period: 57 days.

Average number of offspring: 2.5.

The Neotropical otter shows little fear of humans. All over its range the animal has been hunted for its valuable and beautiful pelt. The durable fur of river otters is used for coat collars and trimming. One estimate has about 30,000 otters being killed annually in Columbia and Peru alone during the 1970's (Nowak 1999).

During the period 1950-1970 L. longicaudis was heavily hunted and its numbers diminished greatly. From 1959-1972, at least 113,718 pelts were exported from the Peruvian Amazon. In Peru in 1970, over 14,000 pelts were exported and some believe this was only 50% of the animals killed (Lariviere 1999).

The Neotropical river otter is listed as endangered by the United States Department of the Interior, Appendix 1 of CITES, and also by the Mexican Ministry of Ecology. It is currently protected by many countries in its range including Argentina, Bolivia, Brazil, and many others (Lariviere 1999).

In Mexico, L. longicauda has disappeared from the highlands. Habitat destruction and fragmentation threatens the otter in the rest of the country (Nowak 1999).

In Argentina, due to excessive hunting in the 1970's, otter populations became very low. Once they received full protection in 1983, their populations recovered rapidly. Continued illegal hunting, water pollution and habitat destruction through ranching and mining are likely causes for the rareness of L. logicaudis (Lariviere 1999). A study of the wildlife in the lower delta of the Parana River in Argentina also shows that extraordinary floods in combination with human pressure has endangered the L. longicauda population there (Quintana et al 1992).

US Federal List: endangered

CITES: appendix i

IUCN Red List of Threatened Species: data deficient

None known.

In the past, the Neotropical otter was heavily hunted for its fur. During 1950-1970 this resulted in this otter becoming extinct over parts of its former range. The retail price of one L. longicaudis pelt around 1990, was U.S. $25-90 (Lariviere 1999).