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Hi, Sept 27, 2008
I get 3.56" and there is a good (probably full) complement of
readily visible sutures, which would indicate 2-year old.
DW
Ronald Arsenault wrote:
> David,
>
>
>
> I have no information on skull length for beavers. However, I did find
> the following on zygomatic breadth:
>
>
>
> Kits: 2.50 - 3.00 inches
>
> Yearlings: 3.20 - 3.40 inches
>
> Two-year olds: 3.50 - 3.60 inches
> Adults: 3.65-up
>
>
>
> (After Patric and Webb 1960 as reported on page 378 in Wildlife
> Management Techniques 1971)
>
>
>
> My apologies for not offering metric conversions (calculator not handy).
>
>
>
> I have no information whether or not Nova Scotia beavers are likely to
> differ in size from the size range indicated above. In addition,
> there is also no indication of the geographical origin of the beavers
> used to determine the above measurements.
>
>
>
> As I recall, one can also use the suture lines as an indication of age
> on mammalian skulls. Easily visible suture lines suggest a young
> animal. These sutures gradually disappear, with the bones fusing as
> the animal ages. Dave, are the cranial sutures readily apparent?
>
>
>
>
>
> Ron
>
>
>
>
> 2008/9/26 David & Alison Webster <dwebster@glinx.com
> <mailto:dwebster@glinx.com> >
>
> Hi All, Sept 26, 2008
> The skull, measured from the bulge that is dorsad of the upper
> incisors to the posterior extremity of the part that articulates
> with the neck, is 129 mm long. I suspect , sheer guess by
> picturing beaver, this is about 3/4 adult size.
>
> The right lower jawbone was missing but, in the left jawbone (in
> looking at this more carefully, I see that the lower jawbone was
> from a different and smaller beaver; both bones were within feet
> of each other near the small dumbell-shaped pond on Little River),
> the curved incisor pulls out readily and is essentially the same
> width (6.2 mm) from one end to the other. This I think follows
> from, if I understand correctly, the teeth growing from the base
> as use wears the cutting edge away. Thus incisor tooth width would
> not increase with age (unless nursing beaver have baby teeth ?).
> Perhaps Randy or Andrew can comment on this. This left lower
> incisor, measured along the curved anterior face is 98 mm in
> length (~80 mm from end to end).
>
> My estimate of 2/3 width, if it applies at all, would apply
> especially to initial cuts where there is no opportunity for
> sideways motion of the chips. Once there is a gap, into which
> chips can by pried, they likely do cut to full width and rather
> than make shavings make fairly thick chips (again by sublimital
> memory) chip size being dependent somewhat on the wood being cut.
>
> Yt, DW
>
>
>
> Ronald Arsenault wrote:
>
> 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 <mailto:srshaw@dal.ca>
> <mailto:srshaw@dal.ca <mailto: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
>