1. Sea otters have the densest hair of any mammal – around 900,000 hairs per square inch (140,000 hairs/cm2). That’s more than 500X denser than the hair on the human scalp, which averages at 1600 hairs per square inch (250 hairs/cm2).
2 Sea otters have individual preferences for prey. Some sea otters prefer to crunch on crabs, while others prefer mussels, even when comparing the diets of members of the same species in the same area.
Food preferences seem to be passed from mother to pup, probably as a result of teaching the youngster how to catch and consume their prey.
Sea otters typically return to the surface to enjoy their catch, making it easier for scientists to monitor their diet from shore. Video credit: Toru Higuchi, youtube
3. Sea otters are the smallest marine mammal. In California, female otters weigh about 50 pounds (about 23 kg) and males can reach up to 90 pounds (40 kg). The largest marine mammal, the blue whale, weighs around 200,000 lbs (about 91,000 kg).
Before you say pipsqueak, you might want to know that otters are the largest member of their family, the mostly land-loving Family Mustelidae, which includes skunks, weasels, and badgers.