One of the most fascinating and endearing behaviors observed in otters is their tendency to hold hands while asleep. This unique behavior is most frequently seen in sea otters (Enhydra lutri), and serves to prevent the animals from drifting apart during their slumber. The otters interlock their forelimbs by holding onto each other’s paws and, in some cases, even form chains with other otters.
The majority of otters sleep on land, either above ground or in dens. River otters in particular are known to find safe and cozy places to rest during the day, often in abandoned beaver lodges. They are opportunistic when it comes to selecting their sleeping spots, and aren’t picky about what type of habitat they choose as long as it provides shelter, warmth, and seclusion.
In general, otters are capable of staying afloat while floating on their backs at the surface of water. This is a natural and comfortable resting position for the animals, and helps to keep their heads above water during the non-REM stage of sleep. They may also bind themselves with kelp to stay secure in place and prevent drifting away from their slumber.
During REM, however, otters roll on their sides and fall below the water’s surface. This is an important behavioral distinction because the occurrence of REM sleep in aquatic animals is correlated with increased vulnerability to predators.