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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 the past. >> >> One of the diagonally cut alder stems had 8 fairly parallel gnaw >> marks. These >> were not fully regular (each was not the exact same width), but they >> were >> spaced on average 3.75 millimeters apart (a bit over 1/8 inch, more >> like 5/64" >> if you prefer inches). >> Would that be a little beaver or a big sucker? >> Steve, Halifax >> >> >> Quoting bdigout@seaside.ns.ca: >> >>> Earlier, I sent a reply indicating beaver... If Chocolate Lake >>> was in >>> Cape Breton, then beaver would have been the only choice; since we >>> have no porcupines. >>> Because only muskrat and beaver were mentioned, was there any >>> indication the culprit came from the water, or was there no visible >>> sign of directionality? >>> Billy
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