• Head and body measure 25.98" to 42.13"
• Tail length is 12.40" to 18.11"
• Total body length is 39.37 " to 60.24 " 
• Weight is from 6 to 31 lbs.
• Small, round head & small eyes
• Short powerful legs
• Prominent long, thick whiskers
• Thick, tapered tail
• Color is dark brown and black on dorsal side, a lighter color on ventral side
• Webbed feet with claws

The river otter tends to travel in pairs and hang out in groups.  They are very playful animals.  They enjoy mud/snow sliding and burrowing through the snow.  By "playing around" they build up strength while still having fun. To keep in touch during all this playing they whistle, growl, chuckle, and scream.  The reproductive patterns of these animals tend to occur in the spring.  At this time the female mates, but the fertilized eggs do not begin to develop until the fall, this is called delayed implantation.  There is something within their body that allows this to occur.  The babies are born 10-12 months after the implantation.  After the birth of the young the male leaves and does not return until he is needed to care for them.  The babies are born blind, so they require much attention from their mother for the first two months.  Within a year they leave their home to begin a home of their own.  River otters live to be about 15 years old in their natural habitat and about 20 years old in captivity. 

River otters are able to withstand the cold waters and weather because of their coarse fur hair.  This hair helps "water-proof" them and keep them warm.  While swimming in the water they can close their ears and nostrils tightly, this helps keep out the water.  While diving their pulse slows down to a tenth of its normal rate to conserve oxygen that will be needed to stay under water.  Otters can go without air for up to eight minutes!  They use a pair of scent glands towards the end of their tail to mark their home territory.

The North American River Otter at the zoo seemed very hyper.  It swam around and was playing with some of its companions.  The signs at the zoo say that the river otter builds its home near water and has underwater openings to the water for easy access and escape.  They also keep two dens, one is for nesting and the other is for use during the day.  These beautiful creatures can swim at 7 mph and on land can run at 18 mph.