Playful river otters are often seen living and swimming into and out of dams. Slides, pathways, and other markings show that the otters are living in the area.
However, otters do not build dams, often causing confusion on who built them.
River otters, in particular, will use abandoned beaver dams. They develop the land around the home by making and marking circuit trails, slides, and nests. Otters use beavers’ dams as a source of protection, access to land and water, and for raising their young. They may also live in other spots such as hollowed logs, piles of rocks, or abandoned burrows.
Read on to learn more about otter habitats, and how they give information about ecological health in an area.
Where Otters Live
River and sea otters have different habitats. The table below outlines key differences between them.
|River Otter: Lontra genus||
|Sea Otter: Enhydra genus||
Note: Since sea otters do not use dams, the information in the remainder of this article will focus on the river otter.
Holt: A River Otter’s Home
A river otter’s den is called a holt.
A holt has multiple entrances and is set in a location with access to water, such as lakes, rivers, marshes, and estuaries. These multiple entrances may be both underwater and on dry land located close to the water line.
An otter’s home can be an abandoned dam or burrow near water left behind by beavers, foxes, muskrats, rabbits, or badgers. Or, otters will aggressively force another animal out of a burrow to claim it as their own.
They may also build nests underneath man-made structures, such as boat docks. An otter’s home could also be a hole in a riverside tree or hollow log or an excavated area underneath trees or rock piles.
Otters often add nesting materials to make the home adequate for their kits (babies), sleeping, and resting.
Otters often use beaver dams, but they upgrade both the area and the dam itself for their needs. These features include creating nesting spots, slides, marked territory and trails, and security.
Beavers will tear apart parts of the dam to let some water out in the winter.
This is to lower the water level inside to open up spaces of air beneath the ice. This will offer the otter shelter and protection as it hunts underneath the surface.
The otter will use local vegetation, such as bark, small sticks, grass, and moss to create nests for their young. Females maintain the den, giving birth to two or three kits annually.
Nests also create spots for resting and sleeping comfortably.
Clearing the Surrounding Land: Slides
Otters will roll around on nearby land close to the water to clear vegetation and to create a “slide”.
These slides are formed on river banks to create a way to enter the water quickly. They can be easily seen formed in mud or snow.
Riverbank slides are 12 inches or wider, with about 6 feet of flattened or removed vegetation around them.
There may be otter footprints or depressed divots, especially where the otters have repeatedly pushed off to slide into the water.
This offers a way to escape predators, such as bobcats and coyotes, and seek safety in the water.
Otters will also create circuitous trails, connecting access to other bodies of water and food sources. These routes can be up to 20 miles long.
Otters mark their land territory with urine and feces or scent-marking.
The feces, referred to as “spraints” come from the anal scent glands of the otters, giving off a fishy smell. Otter scat may have remnants of fish scales, bones, and other waste in it.
Otters also have four glands on the pads of each hind foot. They will shape absorbent materials with their hind feet, leaving the scent behind them.
These piles or scents are often placed along the same spots on a circuit trail, near the riverbank or intersection of two bodies of water, and near dams or habitats.
Otters often use abandoned beaver dams because they offer access to both land and water. They also provide hidden underwater protection from predators.
Indicator Species: Bioaccumulation Of Pollutants
Scientists pay close attention to otters’ habitats and their ecological role.
Otters are apex predators at the top of the food chain. They consume fish, ducks, snakes, turtles, small mammals, invasive species (such as common carp and largemouth bass), and other opportunistically found meats.
Pollutants, such as DDT (dichloro-diphenyl-trichloroethane) and PCBs (polychlorinated biphenyls), build up or bioaccumulate in otters.
Since otters are at the top of the food chain, they consume these pollutants from other food sources, which adds up exponentially in their bodies.
This creates a higher concentration of pollutants that are difficult to effectively eliminate from their internal tissues and organs.
If the otters’ watershed habitat, including food and water sources, becomes polluted, the animals will show increased signs of illness due to a poor endocrine system, low birth rate, and low kit survival.
If a river otter population is strong and active, their habitat is healthy. This indicates that the area is also healthy for other wildlife, vegetation, and humans.
River otters do not build beaver dams.
Instead, they use abandoned ones to create a livable area in conjunction with circuit trails, slides, and nests.
Dams are an ideal habitat for otters as they navigate the water and land for food sources. They also give underwater protection from predators. River otters may also use abandoned burrows, hollowed logs, or piles of rocks near water for their homes.
Otters are apex predators and give important clues to the health of an area and how it impacts other wildlife, local vegetation, and humans.