Males are larger than females. Adult males may measure 48 inches in length, and weigh up to 25 pounds. Adult females are usually 4 to 6 inches shorter, and seldom weigh more than 19 pounds. There are 5 toes on each foot. A web of skin connects the toes on each foot.
Claws are strong and nonretractable.
Otter have 36 teeth, including 4 long and sharp canine teeth. Valves are present in an otter's nose and ears which close automatically as the otter submerges. A pair of anal musk glands are present on both males and females. This musk can be released when the otter is frightened, but it is not as offensive as the musk of other members of the mustelid, or weasel, family. Reproduction Breeding occurs over most of the otter range during March and April, only a few days after the litter is born.