The 13 otter species are members of the Mustelidae, or weasel, family and live in and out of water. For example, river otters reside along streams and waterways in freshwater areas within North America, and endangered sea otters inhabit the coasts along the Northern Pacific Ocean. These carnivores eat a variety of seafood, such as fish, frogs, crayfish, crabs and mollusks. They've been spotted playing with their food before eating it. Sea otters are also known to crack open shellfish by hitting them against rocks [source: Defenders of Wildlife].
Although adult animals often play with their babies or interact during breeding season, unadulterated playtime like this is a rarity [source: Beckel]. In addition to young otters, adult otters regularly engage in play. Studies have found a link between prey abundance and time spent playing -- when food becomes scarce, playtime and social behavior generally disappear [source: Tennesen]. Additional otter observations have confirmed that playtime ranks at the bottom of adult otters' priorities, and the mustelids must ensure that they've satisfied their basic necessities of nutrition and shelter first [source: Tennesen]. Perhaps that's why otters who live in zoo habitats goof off so much.
Specific otter play activities are useful for survival. Take sliding, one of the most common otter amusements. Both wild and captive otters will slide down the same mud or ice path repeatedly. Some scientists have theorized that sliding isn't play but rather a functional way to get around. However, a study of wild otters found that the group slid 16 times in less than a minute [source: Stevens]. Researchers noticed three otters in the study group slid down the same route more than once in a brief time period, indicating that sliding -- while an economical form of locomotion -- is an example of play behavior [source: Stevens].
What about non-aggressive wrestling bouts between two otters? In a study tracking otter wrestling habits over multiple seasons, the otters scrapped more often before mating season than during it [source: Beckel]. Interestingly, in cases when male and female otters wrestled each other, the female initiated the play almost twice as often as the male [source: Beckel]. As with the sliding study discussed earlier, wrestling can also be considered a play activity because of repetition and frequency, with some otters wrestling up to 20 times in an hour [source: Beckel]. The interaction between dominant and submissive otters participating in this type of behavior could reinforce social organization within groups.
During all of this sliding and wrestling, something important happens inside of otters. Activity -- whether through playing, hunting or foraging -- promotes spraint production [source: Carss et al]. Spraint is the term for otters' fecal matter, which they regularly deposit in community areas called latrines. With captive otters, spraint production took half the time when vigorously active, compared to inactivity [source: Carss et al]. Scent-marking with spraint helps otters with species identification, communication and location of potential mates during breeding season. Their numerous spraints throughout the day reinforce territories, thereby preventing conflicts.
From these examples, we learn that otter play is pleasurable but useful. Their characteristic playfulness may help otters survive in their varied environments. And for human children and adults alike, watching them at play brings us enjoyment as well.