NORTH AMERICAN RIVER OTTER
The North American River Otter is a semi aquatic mammal and a member of the weasel family. It is physically well equipped for the aquatic life. Nostrils and small ears close during submersion preventing water from entering. The neck is the same diameter as the head, legs are short and powerful, toes are fully webbed and the tail (one third of body length) is tapered. Smell and hearing abilities are acute. The sense of touch in the paws is delicate and dexterous. Whiskers are long and thick enhancing sensory perception. Fur is short and dense, a good water repellent. Color ranges from light brown to black, but the throat, chin and lips are grayish white. It is a streamlined vision of strength, speed, and agility in the water.
River Otter is a misleading name as they inhabit marine as well as fresh water environments such as lakes, rivers, inland wetlands, coastal shorelines, marshes and estuaries. They tolerate a great range of elevation and temperature and are found throughout Canada and the United States except for areas of southern California, New Mexico, Texas and the Mohave Desert of Nevada and Colorado..
They live in holts or dens such as hollow trees, logs, undercut banks, rock formations, back water sloughs and flood debris. The dens are constructed in burrows of other animals such as woodchucks, muskrats, red foxes, or beaver lodges. They have many tunnel openings one of which generally allows the otter to enter and exit the body of water.
River Otters are polygamous. Females do not usually reproduce until two years of age and males are sexually mature at the same age. They breed from December to April. True gestation lasts 62 – 63 days, but because implantation is delayed for at least eight months, the interval between copulation and birth can reach 10 – 12 months. The young are born between February and April of the following year.
In early spring, expectant mothers begin to look for a den and when they have established their domain, usually give birth to several pups. Each otter pup weighs approximately five ounces and is fully furred, blind, and toothless. The claws are well-formed and facial vibrissae are present. They open their eyes after 30 -38 days, start playing at 5 – 6 weeks and begin consuming solid food at 9-10 weeks. Weaning occurs at 12 weeks and their mothers provide solid food until 37 – 38 weeks have transpired. Their diet consists of an extensive assortment of fish in addition to reptiles, crustaceans, amphibians, birds, aquatic insects, small mammals and mollusks. The maximum length and weight (26 – 42 inches and 11 – 30 lbs.) of both sexes are attained at three to four years of age.
The mothers raise their young without aid from adult males and when the pups are about two months old, introduce them to the water. Otters are natural swimmers and with parental supervision, become more skillful. They can remain under water for nearly eight minutes traveling 400 meters, swim at speeds approaching 11km/h, and dive to depths nearing 20 meters. Otters usually stay with their families, which sometimes includes the father, until the following spring. Prior to the arrival of the next litter, the otter yearlings venture out in search of their own home ranges. They usually live to twenty one years of age in captivity, eight to nine years in the wild.
Olfactory (scent markings) and auditory signals are imperative for inter-group communication. Otters scent mark with feces, urine, and possibly anal sac secretions. Musk from the scent glands can also be secreted when they are frightened or angry.
They snort by expelling air through their nostrils when shocked or distressed by potential danger; snarl or hiss when bothered; whistle shrilly when in pain; chirp like a bird when communicating over long distances and purr when at play.
Aquatic predators are the American Alligator, American Crocodile, and Killer Whale. Land and ice, predators are the Bobcat, Mountain Lion, Coyote, Domestic Dog, Gray Wolf, Red Fox and Black Bear. Most mortality is caused by human related factors such as trapping, illegal shooting, road kills and accidental captures in fish nets or set lines. Death may also be the result of ice flows and shifting rocks. Starvation may occur due to excessive tooth damage. In addition, they can contract jaundice, hepatitis, pneumonia and feline panleucopenia and they have numerous parasites such as ticks, lice and fleas.
River Otters are highly sensitive to pollution and readily accumulate high levels of mercury, organochlorine compounds and other chemical elements. Oil spills, water pollution, acid drainage from coal mines drive otters away and can result in illness and death.
This species is often used as a bio indicator because of their position at the top of the food chain in aquatic ecosystems and are in the category of “Least Concerned” as their numbers are not currently declining at a rate sufficient for a “Threat” category. River Otters frequent Green Cay and may be spotted swimming or meandering through the wetlands foraging, looking for dens or playing. Come visit and enjoy nature’s ever present welcome.
By Stephanie Canter