By
RON TOEL

Mammals are associated to freshwater on land in all sorts of ways, but none of them are as adapted as the whales and dolphins, seals, and manatees are to the oceans.  There are freshwater dolphins in the Amazon River and in the Yangzte River in China; there is a freshwater seal in in Siberia; and the manatee  will go inland in freshwater streams to seek warmer waters, but other than these examples, there really is no need for the mammals of freshwater to develop the specialization of the mammals of the oceans.  The fact that freshwater is limited in extent and discontinuous in space, makes it advantageous for the mammals to make the best of both worlds…..land and water.

There are seventeen species of mammals that are primarily aquatic.  They are the platypus of Australia, the hippos of Africa,  the water opossum and the tapirs of South America and Asia, and the otters, muskrats, mink, nutria, and beavers of North America. One might even add the water buffalo of Asia. Except for the hippos and the tapirs, all have the special adaptations of webbed feet. So that they can swim more easily.

Of these mammals the beaver is by far the most interesting.  It has the ability to turn running water into still water, and streams into ponds.  Being the proverbial industrious busy beaver, and much has been learned and yet to be learned in their cleverness in building both their dams and lodges,  and how they can float large logs to be used in their dam building to the dam site, the beavers are difficult to study.  One just cannot take them into a laboratory and expect them to perform.  Also the fact that they are primarily nocturnal makes them difficult to study in the wild.

Beavers certainly are busy creatures.  This is one of those amazing things that takes place in the natural world, that just cannot be explained.  Who teaches them to build those dams and lodges?   They have been known to build a dam as long as a football field and twelve feet high.  Of course most dams are much smaller.  But these dams can and do change the landscape of an area by creating ponds, which provide habitat for many other animals .  These ponds usually silt up and eventually dry up and the beaver moves on.

Beavers are regarded as pest by farmers as they destroy the crops for their winter cache’.  Their meat is also very tasty, and their fur is very valuable.  Because of this reason, they have been eradicated from all of Europe except for two tiny spots.

Otters are busy too.  However, they are not busy building or working, but instead frolicking and playing.  Mink, a much smaller version of the otter, but take life much more seriously.  They spend less time frolicking and more time hunting for food.  Both usually live in tunnels along the faster moving stream water’s edge and share a similar diet of whatever they can catch.  Fish, and crabs and crayfish are preferred, but will eat other things as well.  They, too, have a very valuable pelt and are trapped for that industry.  Otters are being reintroduced to many area where they had been eradicated, and are making a comeback.

Nutria and muskrats, again are very similar except for size (muskrats are less than five pounds where the nutria can weigh as much as fifty pounds).  They prefer much slower moving or non-moving waters and enjoy the waters edge that is covered with aquatic plant life.  This is where they find their main diet.  They are mostly vegetarians.    They, too, build huts similar in style to the beaver home, but they use reeds and grasses where the beaver uses sticks and mud.  Muskrats are found everywhere in North America. Nutria are primarily a Southern animal, but have been found in as far north as Chesapeake Bay.  They, too are trapped for their pelts and meat.

One can see the similarities of the water mammals, even though they make use of the land as well.  The pelt is how they stay warm in cold weather and water and it is this temperature that makes the pelt very thick and soft is what also makes it valuable.  They all are interesting fun animals to watch and study.

Spend some time along the waters edge and see what is to be found there.