Sunday, November 9, 2014

Castoroides: Prehistoric Animal of the Week

This week we shall be checking out yet another R.O.U.S..  Make way for Castoroides ohioensisCastoroides was a kind of beaver that lived from the late Pliocene, about three million years ago, to late Pleistocene epoch, about ten thousand years ago.  Castroides was amongst one of the largest rodents in history, measuring as much as eight feet long from head to tail and weighing almost three hundred pounds in the largest specimens.  During the Ice Age, these bear-sized rodents would have occupied marshes and rivers all over the Western United States, Florida, and parts of Canada. In life, Castoroides would have coexisted with other prehistoric mammals like mammoths, sabre-toothed cats, Glyptodon, giant ground sloths, giant bison, and early humans.  The genus and species name of this animal translate to "beaver from Ohio"...which makes sense!

Castoroides life reconstruction by Christopher DiPiazza.  I made a slight mistake in basing the tail off that of a modern beaver's.  Many scientists believe Castoroides had a more narrow tail, more similar to that of a modern muskrat's.

Castoroides has many physical characteristics in common with modern beavers.  Like its modern relatives, Castoroides had eyes placed on the top and sides of its head.  This would have given it the ability to see in all directions except directly behind it at any one time while still staying mostly submerged in water.  Because of this it could also be assumed that Castoroides probably had webbed digits to help it swim.  Unlike it's modern cousins, Castoroides had proportionally larger feet, shorter legs, a longer tail, and longer, broader incisor teeth, whereas those of modern beavers tend to be short and chisel-shaped.  The molars were also different in Castoroides than in modern beavers.  This implies that Castoroides was not specialized for chewing trees, and would have sustained itself on a different, softer food source, like water plants.  In fact, the teeth of Castoroides, despite being a beaver, in some ways resemble those of other rodents, like Capybaras, which do eat water plants. There is also no evidence on the fossil record that suggests Castoroides ever built dams. 

Castoroides skeletal mount on display at the North American Museum of Ancient Life.

For a long time Castoroides was one of the most successful large mammals in North America, since its fossils have been found in so many different areas.  It is uncertain why they went extinct, but it may have had to do with drastic climate change at the end of the Ice Age.  Large animals, being more specialized and requiring more food and other resources in order to survive, are usually hit hardest and commonly go extinct first, when their habitat changes too rapidly.  Some also suggest that Castoroides may have been hunted too much by early humans for meat and their pelts but so far no evidence has been discovered that proves this. 

That is all for this week!  As always feel free to comment below or on our facebook page!  Have a Request?  Give me a shout out on either of those two places and i will make it happen!


Kurtén, B. and E. Anderson (1980). Pleistocene Mammals of North America. Columbia University Press. pp. 236–237. 

Korth, William W (1994). The Tertiary record of rodents in North America. Springer. p. 145. ISBN 978-0-306-44696-2.

 "Giant Beaver: Natural History Notebooks". Canadian Museum of Nature. 2011-05-02.

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