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Living Sanibel: The River Otter

By Staff | Jan 12, 2012

By Heather Green

There are 12 species of otters worldwide. This mammal appears on every continent except Australia and Antarctica. The largest of the freshwater species is the giant otter of the Amazonian basin, weighing up to 66 pounds; the shorter but heavier sea otter of the north Pacific coastline can weigh up to 90 pounds. Throughout its range, otter populations are declining as a result of habitat loss and the harvesting-often overharvesting-of its meat and fur.

The only aquatic member of the weasel family, the otter is renowned for its playfulness. Curious and entertaining to observe, it is a favorite at zoos and aquariums. Children seem to gravitate to the otter naturally, as they do with the dolphin. In the wild, the otter is far less playful but is still known to slide down a muddy embankment repeatedly or engage in other behavior that can only be described as having fun. Aside from primates, the sea otter is the only mammal known to use tools when harvesting food.

The diet of the river otter that inhabits all of Southwest Florida is largely made up of fish, both fresh and saltwater species. It prefers slower-moving fish such as gar, panfish, and catfish, but will catch just about any fish it can. It also eats crawfish, horseshoe crabs, frogs, coots, ducks, beetles, and on rare occasions, muskrats and marsh rabbits.

An otter is capable of holding its breath for up to four minutes, diving as deep as 60 feet and swimming as fast as six miles per hour. Its fur is so dense that its skin never gets wet. Young otters, even though they are born with webbed feet and will eventually spend most of their lives in the water, must be taught how to swim by their parents. The otter is very vulnerable to water quality issues and will quickly abandon any polluted lakes or streams. Poor water quality has been a major factor in the otter’s decline worldwide.

The river otter is slowly being reintroduced into states where it once was plentiful, including Iowa, Kansas, Kentucky, Nebraska, New Mexico, North and South Dakota, Ohio, Oklahoma, Tennessee, and West Virginia. Over the past few centuries it has been trapped for its high-quality fur, causing localized extinctions. Most states now prohibit trapping and hunting the otter.

By Dick Fortune and Sara Lopez

The otter is preyed upon by alligators, bobcats, coyotes, and wolves. Because of its unusual method of running, arching its back high into the air as it runs, it is very vulnerable to automobile collisions. Oil spills are especially troublesome for the otter. The Exxon Valdez spill in Prince William Sound killed more than 1,000 sea otters and dozens of river otters within days.

An offshore spill in Florida would not impact the river otter as severely because it tends to favor freshwater over saltwater or brackish environments. The same cannot be said for the manatee, a species that could literally be wiped out along the gulf should a spill like the Deepwater Horizon occur close to the coastline.