9. The Floating Slumber of Sea Otters
Perfectly suited to their aquatic environment, sea otters—those beautiful marine mammals noted for their playful behaviour and tool use—have evolved a distinctive and appealing sleeping approach. While many marine mammals must return to land for rest, sea otters have the amazing capacity to sleep while floating on their backs in the ocean. This sleeping position not only helps them to stay in their chosen habitat but also offers other benefits that support their survival and well-being in the sometimes difficult maritime surroundings. Sometimes with its paws curled across its breast, the picture of a sea otter resting quietly on its back has become iconic of these cute animals and provides an insight into their amazing sleep behaviour.
The way sea otters guarantee they won’t wander away while sleeping is among the most fascinating features of their sleep. Observations of sea otters engaged in a behaviour that can only be characterised as “holding hands” during sleep point to Two or more otters connect paws to create a tiny raft, anchoring themselves to stop separation during their repose. Apart from their pragmatic need, this behaviour emphasises the social aspect of sea otters and the need of group cohesiveness in their daily life. Not only beautiful but also evidence of their adaptive intelligence and social ties is the sight of a group of sea otters floating together, paw in paw, asleep.
Apart from clasping hands, sea otters have another ingenious way of remaining in position during sleep: they anchor themselves with kelp. Often wrapping themselves in kelp strands emerging from the ocean floor, sea otters will essentially be tethered in situ as they float on top. This clever use of their surroundings reveals how well the sea otters may control their surroundings to satisfy their demands. Apart from keeping them from floating away with tides or currents, the kelp gives otters security so they may relax more fully during sleep. In places with lots of kelp forests, which are vital sea otter habitat with food and cover, this activity is very common.
Sea otters sleep in a practical as well as a comfortable posture; their bodies float on the surface and their heads and paws are slightly raised. Sea otters assist retain the insulating qualities of their coat by keeping their fur out of the water as much as feasible. With up to one million hairs per square inch in some places, sea otters have densest fur among mammals. Maintaining body temperature in the frigid seas where they reside depends on a layer of air trapped by this dense fur next to the skin. Given their high metabolic rates and the energy demands of their aquatic life, sea otters minimise heat loss and conserve energy by sleeping on their backs with much of their bodies out of the water.
Regarding sea otter pups, the sleeping quarters become even more carefully guarded and protected. Lack of completely developed fur and body fat that give buoyancy and insulation in adults, young sea otter pups are not yet able to float on their own. Mother sea otters have created a kind and useful solution for this problem: they let their pups sleep on their bellies as they swim on their backs. While still near to its mother, this arrangement gives the pup a safe, warm, dry area to relax. Keeping the pup afloat and sheltered from the cold water, the mother’s body functions as a living raft. Crucially important for early growth of young sea otters, breastfeeding and bonding between mother and pup is also facilitated by this close sleeping position.
Sea otter sleep habits are intimately correlated with their daily activities and energy requirements. High metabolic rates of sea otters are well-known; they must eat a lot of food every day to keep their body temperature in frigid oceans. Their slumber is thus frequently broken with times of grooming and feeding. Usually sleeping in bouts of around one hour at a time, sea otters slumber throughout the day and at night. Their frequent feeding needs are balanced with their need for rest by this polyphasic sleep schedule. Additionally affecting the timing and length of sleep include tides, food availability, and predator or other disturbance present in their surroundings.