River otters may be either diurnal or nocturnal; most are generally more active at night.
Giant otters are strictly diurnal.
Clawless otters are mainly nocturnal, though some individuals may be active during the day in remote areas that are free of human disturbance.
Sea otters are generally diurnal. Daily activities focus on feeding and grooming, interspersed with rest periods.
All otters must continually groom their fur to maintain its insulating qualities. Otters spend a substantial amount of time grooming, and many species of river otters have designated areas on land for drying and grooming their fur. Most vigorously dry themselves by rolling on the ground or rubbing against logs or vegetation.
Researchers have observed sea otters spending at least 11% to 48% of their day grooming. They use their paws and claws to remove debris and to comb their fur. They may also aerate their fur by blowing air into it and beating the water with their feet to whip it into foam. An otter's flexible body and loose-fitting skin allow it to reach every part of its fur.
River otter feces, commonly referred to as spraint by otter researchers, is enormously important in otter communication. Spraint is a visual and olfactory indicator of an otter's presence. Otters produce small amounts of spraint several times a day, depositing it in conspicuous designated areas and spraying it with scent.
Some researchers believe that sliding is a form of play in river otters. For some species, otters of all age classes have been observed sliding. Others believe otters only use these slides for low-energy travel, maintaining that otters generally do not climb to the top of a slope for another slide. These latter researchers have observed very little behavior they interpret as play.
Freshwater otters generally rest and sleep on land, either above ground or in dens. They are not particular about where they sleep and often do so even in areas of moderate disturbance. Individual animals often have several resting places.
Sea otters sleep at sea, floating on their backs on the surface. They often sleep in strands of kelp which keeps them from drifting.
Most male and female river otters form separate dominance hierarchies. The highest ranking males occupy the most favorable ranges. Males and females normally tolerate - but do not accompany - each other. A female with young may become dominant to males.
In Southeast Asia, smooth otters typically occur in social groups consisting of an adult male-female pair and their young.
Spot-necked otters have been observed in groups of more than 6, and as many as 20, animals. On Lake Victoria in East Africa, spot-necked otters may undergo a cycle of aggregation and dispersal, with males and females forming separate groups. A female group may contain 8 to 20 individuals, but become smaller during mating when females pair off with males.
A giant otter social group consists of an adult pair, one or more subadults, and one or more juveniles. Groups with as many as 20 individuals have been reported, but groups of 4 to 8 are more common. Giant otters exhibit a high degree of pair bonding and group cohesiveness.
Cape clawless otters have a clan-type social organization, with groups of related animals associating with one another and defending joint territories. Males may maintain a loose association with a female and her young.
Asian small-clawed otters live in loose family groups of about 12 animals.
Sea otters are basically solitary, but in Alaska they aggregate in large groups of as many as 2,000 animals. Males and females occupy separate sections of coastline, and only come together briefly for mating.
Social and Territorial Behavior
River otters tend to be solitary and fairly territorial. Avoidance is a very significant factor in river otter social behavior.
River otters defend their territories by marking, scratching, and occasionally fighting.
Male river otters ignore females and young through most of the year.
Giant otters are more social than river otters, but separate groups tend to avoid each other.
Clawless otters are relatively social.
Male sea otters set up territories in female areas, and attempt to mate with any female that enters their territory. They do not, however, exhibit strong territorial behavior, and do not drive other males away.