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River otter fascinates with engaging behavior

By Staff | Dec 31, 2009

River Otter (Lutra canadensis) Other names: common otter / Status: FL=stable but extirpated in 11 states and endangered in 13 more, IUCN=LC / Life span: to 20 years / Length (including tail): 26-42 in. (66-106 cm) / Weight: 11-30 lb (5-14 kg) / Reproduces: near water in suitable dens; will often use another animal’s burrow or find natural holes in riprap and tree roots / Found: diurnal in Mangrove Zone, Interior Wetlands.

There are 12 species of otters worldwide. The 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 continued habitat loss and the harvesting 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 Sanibel and Captiva 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 V irginia. It was formerly found in all of these states, but over the past few centuries has been trapped for its high-quality fur, causing localized extinctions. Most states now protect the otter.

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.

On Sanibel and Captiva the otter is a rare sighting. It sometimes frequents the Captiva marinas and can be seen around Buck Key and in the Bailey Tract of the “Ding” Darling refuge. Hurricane Charley in 2004 had a negative impact on the local otter population, though the specific reasons for this are still unclear. Further studies will be needed to determine the true impact hurricanes have on these engaging aquatic mammals.