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- Written by Clyde McMillan-Gamber Clyde McMillan-Gamber
All members of the weasel family demonstrate that species in any family of wildlife diverge into a variety of habitats to take advantage of foods and shelter in each one. That diversion created the many kinds of weasels found throughout much of the world.
All weasel species descended from a single ancestor, which is why they all have characteristics in common, including long, lean bodies; short legs; canine teeth; and being ruthless, secretive, and mostly nocturnal predators.
Weasel species are more common than most people know because those lithe creatures are seldom seen, though they are active all year around.
Each kind of weasel has unique traits, caused by adapting, over time, to a particular niche, apart from its relatives. Those characteristics identify the different members of the weasel family.
Long-tailed weasels inhabit woods, thickets, and farmland across much of the United States. They take shelter in crevices in rock walls, wood piles, and brush piles. And they prey mostly on mice, rats, small birds, and other small creatures on land, sometimes around barns.
Black-footed ferrets are a rare species of weasel in the remaining grasslands of the American Great Plains and prairie. This type of ferret feeds mostly on prairie dogs and other rodents in the grasslands and lives down prairie dog burrows in the ground. Some prairie dog tunnels were abandoned by the ferrets’ killing and eating the prairie dogs that lived in them.
Pine martens live in trees in Canada’s mixed coniferous and deciduous forests. There they hunt red squirrels, flying squirrels, and small birds among the trees. Martens live in tree cavities, some of which they obtained by killing the squirrels that lived in them.
Mink are semi-aquatic. They live along streams and creeks in woodlands and thickets in much of the northern hemisphere. There they prey on crayfish, frogs, small fish, mice, muskrats, and other small wildlife. Many mink live in muskrat burrows in stream banks, after those large rodents were dispatched and consumed by the mink.
River otters live along creeks, rivers, and lakes, where they mostly catch fish. Otters are naturally streamlined in the water and are speedy swimmers in it, which helps them catch fish.
Sea otters live in the Pacific Ocean, near shore. Probably close relatives of river otters, sea otters’ ancestors gradually adapted to living in the ocean and diving to the bottom to bring up sea urchins, mollusks, and other sea critters to ingest.
Sea otters learned to float on their backs on the ocean surface and use their front paws to hold small rocks to hammer open their sea-critter cuisine, which the otters balance on their furry bellies. What a distinction between pine martens and sea otters.
Exploiting different habitats and food sources, over time, created the various weasel species throughout the world. And they are just one example of divergence causing new species on Earth.
Clyde McMillan-Gamber is a retired Lancaster County Parks naturalist.