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Index of Subjects ------=_Part_34015_21687324.1222305806425 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Content-Disposition: inline Hello Steve, Dave and others, As everybody seems to be in a confession mode.... I made an assumption that may be erroneous should Dave's suggestion be correct. It is actually the gnaw marks of an adult beaver which measure approximately 6 mm in width. I assumed a this represented the width of the teeth of an adult beaver. If Dave's suggestion that the width of the gnaw marks represent 2/3 of the width of the incisor teeth is correct, then an adult beaver would have incisors 9 mm wide. Dave, is the skull you have that of an adult beaver? However, the above does not change my initial conclusions that the evidence still strongly points to a beaver (the presence of muskrats does not exclude beaver) and that the beaver responsible for the cutting was likely a sub adult. Ron 2008/9/24 Steve Shaw <srshaw@dal.ca> > Hi Dave and others, > No Dave, your note didn't come through on NNS, only the recent one direct > to me. One of my earlier 2 posts came through in the wrong order, though, > and NNS has seemed erratic or slow sometimes, recently, as others have > noted. > > Yes, you caught me with an inexcusable error when I converted 3.75 mm to > 5/64 inch (thinking that some out there may not like millimeters) when it > should have read approximately 5/32 inch. Actually I missed this error > because I didn't convert it arithmetically but stuck a ruler next to two > lines I'd drawn, and mis-read 32ths as 64ths on the ruler. ( No, I'm not > the guy who designed the lens in Imperial for the Hubble telescope which was > then made in metric units, or was it the other way round?). However and in > consequence, I'm VERY glad to find that you made complimentary (admittedly > smaller) error: 3.75 mm is actually IS a little bit larger than 1/8 inch, > not smaller -- I make it 1.181 eighths-of-an-inch if you want to get fancy. > > To be serious, your reply is useful because it helps to clarify my original > short post on this beaver size thing, which may have been well-intended but > was a really ill-conceived as written, I've realized since. The round > alder branches were gnawed at a shallow angle, so the en face view of the > cut was roughly elliptical, with the long axis of the ellipse in line with > the branch. The branch and the long axis of the cut would actually have > been parallel to the axis of the beaver's body as it stood up in the lake to > gnaw away. But the 8 or so gnaw marks that I measured as 3.75 mm each, ran > ACROSS the ellipse (i.e. parallel to the short minor axis of it). This > would have been orthogonal to (at right angles to) the beaver's incisors, > not parallel with them! It then makes no sense to ask (as I did) how wide > the teeth are in a beaver of a certain age in relation to these cuts: the > marks will not be related to tooth width, but to the depth of each of the 8 > chisel-cuts it made in lopping off the branch, as you correctly point out. > So the question should be reformulated to ask how long or deep is each of > the series of chisel-cuts made by a beaver of a certain age or size, > probably harder to assess accurately. From Ron Arsenault's reply that the > teeth on an adult are about 6 mm wide which agrees with your specimen, it > sounds like you may have an adult beaver skull in your possession. If your > estimate of a cut-depth of 3.4 mm for such a beast is realistic, "ours" then > could have been a pretty large beaver. > > I also put the local observations round an e-mail list for people who live > on Chocolate Lake here, and a few replies revealed that a muskrat called > Charlie lives under a neighbour's dock, eats his irises and hostas and has > even been seen swimming back home with lake vegetation in its mouth. This > has prompted humorous bets which so far rate the likely identification of > the culprit as muskrats 2, beavers 1 (I'm the '1'), but no-one has seen the > muskrat eating woody stuff including alders, and these are mostly townies > whose opinions may not be reliable as those of folk who actually know about > beavers, to put it mildly. The clincher may be a third hand report from a > few days ago that a workman actually observed a beaver swimming towards the > water inlet pipe for the lake with a bundle of sticks, and my bet is firmly > on a beaver. If correct, we may be about to experience a drop in lake > level that has little to do with global climate change. > Steve > > ***************************************** > On 24-Sep-08, at 2:15 PM, David & Alison Webster wrote: > > Hi Steve. Sept 23. 2008 >> I sent this yesterday to Naturens but for some reason it didn't get >> through so will send it offline to supplement your fund of gnawledge, >> especially beaver gnawledge. >> Also I notice that I said 3.4 mm apart when I intended to say 3.4 mm >> wide, i.e. ridges 3.4 mm wide (& ~ 4.00 mm apart). >> And that 1/8' was intended to be 1/8" >> Yt, DW >> >> -------- Original Message -------- >> Subject: Re: [NatureNS] beaver - size estimation >> Date: Mon, 22 Sep 2008 12:10:41 -0300 >> From: David & Alison Webster <dwebster@glinx.com> >> To: naturens@chebucto.ns.ca >> References: <BE20011C928B4CC38A2D1CEBD6F14ABF@bernard> < >> 50035.216.118.137.234.1222010582.squirrel@webmail.seaside.ns.ca> < >> 20080921185446.h82rrgkcqvusococ@my4.dal.ca> >> >> Hi Steve & All, Sept 22, 2008 >> The incisor teeth of a beaver skull, that I happen to have, are 6 mm >> wide at the cutting edge and are spaced 1.4 mm apart. The teeth have a >> curved face like a gouge (1/4" #7 spoon gouge as shown in Lee Valley) and >> to avoid torn wood, buried teeth, splinters between teeth, shavings that >> don't curl well, damaged cutting edges etc a wise beaver would never cut to >> the full depth of the curve (i.e. full width of the cutting edge) and likely >> would seldom use more than 2/3 of the cutting edge. >> >> Thus this beaver would likely have left ~parallel ridges of wood at >> least 3.4 mm apart so this fits your 3.75 mm well. >> >> BTW 3.75 mm is less than 1/8' and 4 x 8 =32 not 64 :>). >> Yt, DW >> >> Stephen Shaw wrote: >> >>> Hi again Billy, or anyone else, >>> As an afterthought on a recent reply from me about this, could an >>> experienced >>> woodsman tell the approximate size of the beast from the spacing of its >>> gnaw >>> marks? Somebody must have looked into this in