The North American River Otter

The Deep Stuff

A Quick Overview

We all know the river otter: what it looks like, where it lives, what it eats and what eats it. But now we will take a closer look at our furry little friend. We will be diving into different subjects like its fossil record, morphology, a DNA analysis, its embryology, a geographic distribution of a related species, and a bit on artificial selection. Enjoy!
River Otters - The Wild Center

A Little Video on Our Little Friends

Here's a special video with a little overview on the north american river otters, Squeeker and Squirt. Special thanks to The Wild Center!!!!!

The Fossil Record of a River Otter

Around 5-23 million years ago, scientists found through molecular biological techniques that the river otter and giant otter separated into their own species. This occured in the miocene period, around 5-23 million years ago (1), which was, however, earlier than what the fossil records indicated (3). The fossil records showed that this divergance had occured in the late pliocene period, which was 3.6-1.8 million years ago (1).

A River Otter's Morphology

Over time, the river otter has changed and adapted in many ways. According to our fossil records, most of the ancient species of otters were a form of a giant river otter. As time passed, different species of otters began to come about; species such as the sea otter, the north american river otter, and the giant otter mentioned earlier (1). As the north american river otter adapted to its watery enviroment, special changes, including the closing of its nostrils under water, occured (2). Today, the average river otter is about 40 inches long (head to tail), and about 30 pounds. Its fur coat contains two layers: an inner coat and an outer coat, in which the inner coat contains more fur (2). Its whiskers are highly sensative to vibrations underwater, and it has short, webbed feet to move fast in the water.

DNA Analysis of a River Otter

According to our fossil records, most of the ancient species of otters were a form of a giant river otter (1). As time passed, different species of otters began to come about; species such as our north american river otter, the marine otter, the southern river otter, and a few more (4). In the cladogram below, you would find the north american river otter with the sea otter.

Embryology and Reproduction of a River Otter

A female north american river otter often spends most of the year when it comes to reproduction. It first starts with a 1 month period, where the fertilized eggs are formed. However, the eggs don't begin to form for about 7-10 months, and then around 70 days later, a litter of 2-3 kits are born. The female otter isn't limited to just two or three kits per litter, there have been up to 6 kits in a litter (5).

Geographic Distribution of Otters

A north american river otter (top picture) can often be found in mostly in Canada as well as the Atlantic Coast and the Pacific coast. They have also been found in the Gulf Coast (1). Another closely related species would be the marine otter (bottem picture), also known as the sea otter, is often found in the south western regions of South America, in countries such as Argentina, Chile, and Peru. Some have even been spotted in the Falkland Islands (6).

What Have We Done?

As time has passed, we have found ourselve closing in on our otter populations. No need to press much worry, for the north american river otter isn't an endangered species as a whole, but it would help if we dialed it down on the trapping for pelts. Around 20,000- 30,000 otters are killed for their fur each year (5). We have also been causing river pollution with factory fumes and dumping our trash in the streams as well as poor waste management in the cities. Another cause is our continuous movement and building in habitats of otters. Otters are extremely shy, and as we move, we continuously push them into smaller and smaller habitats (5). We can do many things to help stop the decrease in the north american otter's population, such as not dumping trash in our streams and tributaries as well as banning fur trapping in certain places.