Otter Pups Can’t Swim, Here’s How Moms Turn Babies Into Buoys

Otter babies fur inflates like a life jacket, but before they hunt, moms need to find a way to secure their pups so they don’t float away.

Sea otter pups lay on their mom’s chest as she floats on her back because they cannot swim. An intriguing fact, considering sea otter pups are born in the water whereas other aquatic mammals go onto the shore or ice in order to deliver their babies. In addition, sea otter pups are the most altricial aquatic mammals – meaning the babies are helpless and would die without their moms.  

Sea otters can be found in the frigid kelp forests of Northern California, and would not survive the cold without their specialized fur. It is the densest of any mammal on Earth, with up to a million hairs per inch. Because of their fur’s density and texture, otters are able to sustain a layer of air directly next to their skin.

Warmth requires constant maintenance. Mother otters spend many hours a day grooming herself and baby so they both can keep a layer of warm, dry air. This layer of air also acts as a self-inflating life jacket, so baby otters can float in the water.

This is useful during feeding time. Before a mother goes hunting, she has to find a safe place to leave her young otter behind. She’ll blow air into her newborns fur to make the baby float. But to make sure her newborn doesn’t float away, mom will typically find a blade of kelp to act as an anchor.

Once her newborn is secure, the otter mother will dive into the kelp forest to look for clams and oysters. Hunting is serious for otters. Since they don’t have blubber to help store energy and fat, otters need to eat the equivalent of around 20 to 25 percent of their body mass in food every day to survive. That percentage is even higher for females nursing a newborn. So when she isn’t grooming, mom spends her time scanning the floor for food. Mothers also have to hunt quickly to prevent predators from attacking her young otter floating on the surface.

Once the mother gets back to her baby, she quickly eats her own meal using rocks as tools to break open the food. Then it’s the babies turn to eat. Mom will nurse her newborn for the first six months of its life The energetic needs of growing pups remain extremely high. The ‘End-of-lactation-syndrome’ is a term applied to mothers that make the ultimate sacrifice for their babes, and it’s implicated in a significant number of deaths in California otter populations.

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