FLORIDA’S RIVER OT­TERS

One of na­ture’s more lov­able faces

RSWLiving - - Departments - BY WIL­LIAM R. C OX

The river ot­ter (Lon­tra canaden­sis) is a mem­ber of the weasel fam­ily, Mustel­idae, in the or­der Car­nivora. This semi-aquatic mam­mal is 3 to 4 feet long, in­clud­ing its tail, and weighs 11 to 30 pounds. The fe­male is smaller than the male. The river ot­ter has black to brown fur, with a lighter brown on its face and belly. It has short legs with webbed feet with five toes. Its body is long and nar­row with a flat­tened head. Its strong tail is one-third the length of the body.

Be­cause of these body fea­tures, the river ot­ter is an ex­cel­lent swim­mer and thrives in wet­lands, ponds, lakes, streams, canals and es­tu­ar­ies. It can stay un­der wa­ter for four to eight min­utes chas­ing its prey, which in­cludes cray­fish, snakes, tur­tles, crabs, small al­li­ga­tors, birds and fish. The river ot­ter is even known to prey on rab­bits and muskrats. Its long whiskers help de­tect prey in dark and murky wa­ter. Its long nails help them hold slip­pery prey, and its sharp teeth help catch and chew prey.

The river ot­ter has a large home range. The fe­male’s range is 12 square miles when ac­com­pa­nied by young for ap­prox­i­mately a year, then in­creases to 30 square miles with­out young. The male home range is 60 square miles. The fe­male home range is lo­cated in the best feed­ing ar­eas and does not over­lap with other fe­males. The male home range does not over­lap with other males, but does over­lap with sev­eral fe­males. The only time the male spends time with the fe­male is dur­ing the fall and win­ter mat­ing sea­son in Florida when the fe­male is in es­trus.

Ot­ter mat­ing sea­son runs ap­prox­i­mately from Novem­ber through April. Es­trus lasts only six weeks with re­cep­tiv­ity to the male oc­cur­ring about ev­ery six days. The fe­male re­leases es­trus scents at prom­i­nent points such as ot­ter la­trines (scent posts), dens or rolling places. There can be as many as 40 scent posts within a half mile of suit­able habi­tat. The fe­male ot­ter has a de­layed im­plan­ta­tion where the fer­til­ized egg cell does not de­velop un­til im­planted in the wall of the uterus nine or 10 months later. Ges­ta­tion takes ap­prox­i­mately seven weeks. Young cubs are born in a den with two to four per lit­ter. The fe­male has one lit­ter per year or ev­ery other year.

The river ot­ter does not ex­ca­vate its own den. Ot­ter dens are se­lected in nat­u­ral cav­i­ties along a ditch, creek, wet­land bank, hol­low stump or log. I have found ot­ter dens in large pipes along drainage canals. Dens are one to two feet above wa­ter.

At birth the cubs are fully furred but their eyes are closed and they have no teeth. Af­ter five weeks they open their eyes and play with each other. The cubs are not seen out­side the den for 10 to 12 weeks. They are given solid food at this time and are weaned sev­eral weeks later. They have to be taught how to swim as they have a dif­fi­cult time keep­ing their head above wa­ter. A male is not al­lowed to come near the cubs un­til they are 6 months old. A male is sex­u­ally ma­ture at 2 years, but is not usu­ally suc­cess­ful un­til 6 or 7 years old.

Be­cause of their large home ter­ri­to­ries, river ot­ters travel long dis­tances over both land and wa­ter, cross­ing many road­ways, which re­sults in many road kills. The ot­ter is most vul­ner­a­ble to pre­da­tion when on land as it is very clumsy out of wa­ter. Although it can run up to 15 mph, it is eas­ily caught by coy­otes, bear and bob­cats. It can live up to eight or nine years in the wild or 20 years in cap­tiv­ity.

The great­est chance of ob­serv­ing an ot­ter is from dawn to mid­morn­ing and near sun­set. It spends the ma­jor­ity of the day groom­ing and sleep­ing. It can be ob­served through­out Florida, with the ex­cep­tion of the Keys. I have ob­served river ot­ters in South­west Florida along fresh­wa­ter wet­lands, lakes, ponds, streams and es­pe­cially canals and ditches. Dur­ing drier times of the year ot­ters can be seen at Six Mile Cy­press Slough. I have also seen them in saltwater en­vi­ron­ments on Sani­bel and Cap­tiva is­lands. I have ob­served river ot­ters tak­ing bait out of live wells of fish­ing boats at Bar­na­cle’s Is­land Re­sort (for­merly Bar­na­cle Phil’s) on North Cap­tiva and the Green Flash Wa­ter­front Restau­rant on Cap­tiva Is­land and in Bray nerd Bayou near the north­west tip of Buck Key.

Wil­liam R. Cox has been a pro­fes­sional na­ture pho­tog­ra­pher and ecol­o­gist for more than 35 years. Visit him on­line at wil­liam rcox­pho­tog­ra­phy.com.

River ot­ter

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