External Anatomy
* Otters range in size from 65 cm (Asian small clawed otter) to 180 cm (giant otter) long from nose to tail.
* Otter tails are long and strong. The sea otter has, comparatively, the shortest and least muscular tail of all of the otters.
* All species have long, flexible bodies designed for speed and agility, especially under water. River otters can run ~20 mph (likely faster in bursts) and giant otters can swim 9 mph.
* All otters, except sea otters, have anal scent glands at the base of the tail used for scent marking.
* Fur is very dense and usually very silky (composed of guard-hairs and fine under-hairs) and varies through shades of brown, frequently with lighter undersides and/or spots.
* Otters can close their ears and noses underwater.
* Otters have very good hearing.
* Noses are one of the distinguishing features between otter species, some even have hairy noses! Otters have a good olfactory sense (they have a good sense of smell!). They all have vibrissae (whiskers) that are so sensitive they can sense under water vibrations! (this is very helpful in detecting prey)
* Feet are generally webbed with claws. Otters' feet are distinctive and say a lot about where the species live. The soles of all otters' feet are hairless, except for the sea otter whose hind feet are furred.
Internal Anatomy
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| Internal Anatomy. L. Spelman 1994 |
* Otters hold their breath to dive for food, escape predators, and, likely, for fun! River otters can hold their breath 6-8 minutes. The longest sea otter dive recorded is 4 minutes 25 seconds (though they can likely hold their breaths a little longer).
* Otters have a higher rate of metabolism than most similarly sized mammals. Water conducts heat much faster than air, so they are constantly working to keep themselves warm. The super-dense fur just isn't enough to do it on its own, so they have to eat a lot!
* Otter's eyes have specialized lenses and corneas that correct their vision for the change in light refraction between air and water environments.
Some links to additional anatomical exams and necropsies:
* An interactive cryo-cross-section of a sea otter fetus.
* Step-by-step river otter dissection .
* A comprehensive "pictorial guide" of sea otter anatomical exams and necropsies from US Fish and Wildlife Service, Region7, Alaska Veterinary Pathology Services, and Alaska Sea Life Center.
