Sociable

Thursday, 4 November 2010

Provenance and Some Physics

Now, here is the abstract of a very interesting paper by Duncan Halley on the important subject of what kind of beaver you should get if you are thinking of restoring the species to your country.

onlinelibrary.wiley.com/doi/10.1111/j.1365-2907...x/abstract


In Scotland the official line is to go for beavers from Norway on the grounds that they resemble most the few skulls and bits of jaw that are preserved in the National Museum of Scotland. This seems reasonable enough until you learn that the beavers of Norway lack genetic variety and so could be vulnerable to various problems. It would be worth following the link that I have given to learn more about this.


To my mind the choice of the genetically more diverse beavers from Bavaria makes a lot more sense as candidates for returning to the rivers of Scotland, but there you go.




I had not visited the Wet Wood for about a week, so I thought I should take a walk along there this afternoon. Here is the dam that stops the main ditch and the pond that lies next to it. A little to the left of the dam you can make out the still exposed top of the straining post of a fence. You will find a recent photograph of this post and a shot I took back in 2002.



Here is that straining post as it was this afternoon.




Further into the wood I found that the beavers have been working on the canal. 

My copy of 'Beaversprite' arrived this evening. Reading through President Owen Brown's editorial I found this interesting information. 



'Did you ever wonder how a
beaver can pull a 20-40 pound floating
log through the water? A log that may
weigh more than half the beaver’s
weight? PHYSICS!
Oh my, why did I bring up a
subject most people avoided or hated
in school?. Well, here is the answer.
Weight is the pull of gravity on the
Mass of the log and can be represented
by the equation W = M x g where g is
the acceleration due to gravity and is
9.8 (I will
leave off
the units
to the
chagrin of
all of you
who like
physics).
What this
means is Weight is nearly ten (9.8)
times the Mass, so what the beaver has
to pull through the water is only one
tenth of the Weight. Now the beaver
only has to apply a force of two pounds
(lbs.) for a 20 lb. log and four lbs. for a
40 lb. log. Who would ever think that
physics could be so illuminating!!!'

I have often wondered about the relative cost to the beaver of digging a canal to float timber down it and the cost of dragging branches to a dam or lodge. 

By the way, I have left the quotation in the form it pasted into my post rather than reorganise it.


Here is the web address of Beavers, Wetlands and Wildlife: http://www.beaversww.org

BWW is an excellent organisation, whose purpose is, among other things, to show how people and beavers can live with each other.



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