River Otter
(lontra canadensis)
Amongst the wildlife that live in and around Hotel Lake, it is always a pleasure to catch a brief glimpse of an otter. Such sightings of our local river otters (lontra canadensis) are usually highly animated, funny and cute; they always seem to be in motion. On those rare days when ice forms on the lake, otters delight in running and launching themselves and sliding across the ice as otter-toboggans. These intelligent and resourceful creatures can be seen solitary or in groups. They are inquisitive but also secretive and shy, and in rare cases, aggressive. Lets take a closer look at this delightful neighbour.
Range of the North American River Otter
Shyamal, Public domain, via Wikimedia Commons
North American river otters inhabit a wide range on our continent. They live in every Canadian province and territory except PEI where they are said to be extirpated (meaning eradicated or exterminated). They do not inhabit desert or tundra landscapes. River otter populations in Canada tend to be found in rural or wilderness areas (except southern parts of our prairie provinces) and in coastal regions where they inhabit lakes, rivers and wetlands and even our coastal shorelines.
River otters are semi-aquatic mammals related to weasels, mink, stoats…and others in the Mustelid, family. They are carnivorous and hunt primarily for fish, mussels and crayfish as well as other animals and even plant life. They have sharp canines and carnassials (teeth adapted to shear flesh).
Adult river otters have muscular and elongated bodies which can measure up to 1.4 meters long and weigh up to 14 kg. They are highly streamlined with a long tail for aquatic efficiency and agility. Their water-repellent fur is primarily dark brown (when wet) with dark grey undersides. A thick layer of fat lies under their skin providing insulation. They are capable of diving up to depths around 20 meters and can remain underwater for up to 8 minutes and travel long distances below the surface. Webbed feet propel them underwater at astonishing speeds up to 11 kilometres per hour. Like beavers, river otters close their ears and nostrils when underwater. They have a third eyelid for added protection. The long whiskers around their noses, called vibrissae, play an important role in finding food when hunting in dark or turbid waters.
They are equally comfortable and mobile on land and can run as fast as 24 kilometers per hour, which is much faster than we humans.
Differences between river otters and and beavers.
At any time you are on the water or walking around Hotel Lake you might suddenly see a river otter. Or is it a beaver? With careful observation it is quite easy to tell the difference
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Differences between river otters and sea otters.
Although it is very unlikely that we might find a sea otter in Hotel Lake, it is not uncommon for our river otters to to roam freely in North Pender Harbour and to be sighted along our ocean shoreline. In order to differentiate between sea otters and river otters the first thing to know is that the river otters we see in Hotel Lake are the smaller of the two, about 1/2 to 1/3 of the size of sea otters. Our river otters are primarily dark brown (when wet) with lighter shades on the underside of nose and chest. Sea otters have lighter fur in the head, neck and chest areas. The river otter has a very long and pointy tail (about 1/3 of its total length) while the sea otter has a shorter and rounded tail. The sea otter has large webbed feet while the river otter has short legs and smaller webbed feet. And, while sea otters are well known for floating on their backs, river otters simply don't do that. River otters are equally comfortable and nimble on land as they are in the water but sea otters rarely leave the water. When sea otters venture on land its called "hauling out" which can be for various reasons such as safety and to warm up, but they are awkward and slow moving on land.
The life of an Otter
River otters are known to live for about fourteen years in the wild. Males may live alone for periods or can congregate in pairs or larger groups of males. Females raise successive litters of young pups to adolescence.
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Female river otters may give birth annually but most tend to reproduce every two years, delivering as many as 6 pups, but with litters of 2-3 pups being most common. Adult males are polygamous and travel in search of females in the early spring when breeding takes place. Once pregnant a process called delayed implantation commences, where the fertilized otter eggs begin to develop into embryos, but then stop development and float freely in the uterus for about 7-10 months. Then, triggered to implant onto the uterine wall, embryo development continues for about 70 days until birth. This delayed implantation process means that gestation takes as long as a a year to complete and this results in births that occur usually in March or April when the temperatures are warming and food is abundant.
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Otter pups are born fully furred, blind and weigh about 140g. They remain in the den with their mother, for about a month before venturing out and being introduce to the water. A month later the pups, now fully sighted, are taught how to swim by the mother. Pups stay with the mother, swimming and hunting, for about one year and disperse at roughly the same time that their mother is about to produce another litter. The pups, now on their own, reach sexual maturity when they reach two years of age although young males may not mate until they reach the age of five to seven years.
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River otters are nocturnal and therefore most active between dusk and dawn but they often extend their activities and hunting into the mid-morning. Their daily foraging movements can routinely take them between 2 and 5 km per day as they search for food or explore new territory. The river otters in Hotel Lake can often be seen in mornings as they patrol around Hotel Lake's shoreline. In calm water conditions, the otters swimming underwater can be visually tracked because they leave a trail of fine bubbles on the surface. It is very impressive to watch how fast this trail of bubbles materializes as the otter streaks along below the surface.
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Playful activities such as sliding and tail chasing, combined with burrowing and hunting are all part of a young otter’s upbringing. Often seen “frolicking” river otters will delight in any chance to slide on mud, grass, snow or ice.
These highly active and flexible creatures communicate with each other through body language as well as various vocalizations which include low growling, yelping, whistles, screams and high pitched chirps.
River Otters and Territory
River otters can be territorial concerning dens and their young pups and they mark their territory by urination and defecation and also the release a strong odour from scent glands at the base of their tail. However, territory is not as important to otters as the availability of food along shorelines. It is food availability that can cause otters to relocate to other water bodies where food is more plentiful.
While otters may move about and relocate, they tend to remain generally in the surrounding area of about 8-40 square kilometres. A quick look at a 4 kilometer diameter circle over the North Pender area reveals that all our lakes and most of the salt water shoreline are in a 14 square kilometre area. This means that the otters we see on Hotel Lake may, over time, migrate elsewhere to other lakes, streams or ocean shoreline; conversely other otters may move to and take up residence at Hotel Lake.
River otters build or occupy dens along the shoreline of their aquatic home. Although capable of limited burrowing they prefer to occupy existing dens or to take advantage of existing spaces beneath trees, amongst deadfall and even in small caves along the shore. A common characteristic of otter dens is the presence of two or more entrances with one being underwater to enable the otters to access the lake or stream during winter freeze up.
River otters do not store food for the winter, nor do they hibernate. Their high metabolism and rapid food digestion requires that they remain actively hunting all winter which is why they can be seen all year long. If ice forms on Hotel Lake they will explore gaps in the ice to breathe and can often be seen playing and sliding around on the ice surface. Their high metabolism drives them to constantly hunt and as there are very few predators that hunt them, river otters are considered to be apex predators.
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Apex Predator
An apex predator is at the top of the food chain. When river otters are on land or frequent the shores and bays of the ocean they are vulnerable to higher predators. On land, river otters may face attack by bears, coyotes, bobcats cougars and dogs. However, adult river otters in an aquatic environment such as in Hotel Lake, face no predators that hunt and eat them which means they are considered apex predators. It is only the young river otters who are susceptible to predators.
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A river otter's wide range of food preferences starts with fish such as carp, sunfish, minnows, suckers, sculpin and salmon but they will also eat just about anything they come across such as bivalves, mussels, snails, crabs, crayfish, as we’ll as turtles, frogs, snakes, beetles and worms and, the list goes on to include opportunistic meals of fish, bird, and snake eggs. Small mammals such as mice or young muskrats and beaver are also food for river otters and to round out the diet, river otters can also be seen munching on Hotel Lake’s aquatic plants and tubers.
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As apex predators, river otters help thin invasive species and protect biodiversity. Without river otters, watershed food webs would suffer. Protecting these fascinating and playful animals will aid many species.
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Realistically and historically adult river otters face only one ultimate predator, humans! In the past humans over-hunted otters. Today, humans continue to take a detrimental toll on river otters when they cause otter-habitat-loss or pollute water habitats.
River Otters and Humans
They are cute, playful and intelligent. They are also carnivorous predators who are primarily concerned with hunting for food. They exhibit territorial behaviour in the protection of their dens and also the safety of their young pups and other members of their group. Their reaction to humans is one of flexible tolerance and yet isolated cases of aggressiveness have occurred in the past.
A river otter’s aggressive capabilities must be acknowledged and respected. They are equipped with pointed canine and incisor teeth as well jagged molar and premolar (carnassial) teeth. They have a powerful bite, very much like a dog bite. Their web feet are equipped with claws. They are muscular, highly mobile and agile in their aquatic environment. They are unmatched swimmers. On land they can run much faster than most humans.
In a 2011 study of violent otter attacks against humans, most of the cases studied occurred in North America. 77% of the otter attack cases studied involved river otters. Rabies was confirmed in 66% of the documented cases that were studied. In some cases pet dogs or other humans were also attacked. Injuries ranged from nips to deep gashes requiring stitches. One fisherman “trapped a cub (otter cub) in his net and a group of otters gathered and attacked with the result that he died from scratches and bites”.
Efforts in recent years to reintroduce the otter and increase populations in North America have been successful and the study found that otters, although somewhat territorial, tend to avoid areas of human activity.
On the other hand the encroachment by humans into otter habitats may be one reason for the increases in otter attacks in recent years. Most attacks on humans occurred while the human was swimming in a pond or lake or walking along a river.
Threats
During the late 1800s, river otter pelts were in high demand and trapping resulted in a sharp decline in population. This was reversed when conservation efforts succeeded in the reintroduction and protection of this species. Today the river otter population in Canada is considered stable and thus they are not currently at risk. In British Columbia the river otter is officially designated as a Class 2 furbearer and can be legally harvested, but only by licensed trappers. Perhaps because the demand for otter pelts is low, British Columbia does not currently have any quota or bag limits or compulsory inspection nor are there any reporting requirements for the trapping of river otters.
How can we help?
As we gather information about the river otter and share that with you, we hope to develop a better understanding of the environment and the true and natural circumstances of our lake and its wildlife.
For the river otters in Hotel Lake, to survive, they need a healthy aquatic habitat. The river otters that we see on a daily basis, hunting, eating, rolling, sliding or playing with litter mates are simply being themselves. They seem to thrive in the hottest weather and are equally active and happy sliding across frozen ice on Hotel lake. Because they seem so energetic and playful, it is hard to believe that our local river otters need any help at all. However they they are seriously affected by any pollution in their environment. They are also susceptible to human interference or the destruction of their shore-line habitat and their dens.
We can help by doing our best to prevent pollution in Hotel Lake. Water quality is just as important, to the our river otters as it is to we humans.
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We can help by preserving the natural state within the Riparian Area around the lake because this is where river otters make their dens.
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We should also avoid disturbing otter dens around the lake and keep a safe distance.
Although they may seem playful and harmless, never approach a river otter. They are known to attack humans and their pets on water and on land. When cornered on land or in the water they may attack, fight, bite and scratch. A female otter with young pups can be very defensive.
Be respectful, keep away, maintain a safe distance at all times.
Library of references:
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E-FAUNA BC: ELECTRONIC ATLAS OF THE WILDLIFE OF BRITISH COLUMBIA
Lontra canadensis (Schreber, 1777), River Otter, Family: Mustelidae. introduction to the Mammals of BC
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A REVIEW OF VIOLENT OR FATAL OTTER ATTACKS Michael BELANGER, Nicole CLOUGH, Nesime ASKIN, Luke TAN, Carin WITTNICH. Oceanographic Environmental Research Society, Barrie, Ontario, Canada.
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FURBEARER MANAGEMENT GUIDLINES, River Otter, 2003, document formatted for insertion into the BC Trappers Association Trapper Education Training Manual.
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