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Sex of a beaver

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TimR

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Nov 25, 2009, 8:43:14 AM11/25/09
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I sometimes stop for an intact roadkill, if it's one I don't have a
good photo of.

I found a couple of beavers this week, in such good shape I'm not sure
what killed them. I was asked if they were male or female.

There were no external genitalia - if they were dogs I'd conclude both
were female, but I'm not sure what a male beaver looks like. I asked
a couple friends who trap, but they said they just skin them without
caring about the sex.

Frank

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Nov 25, 2009, 6:47:16 PM11/25/09
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Inquiring minds want to know. Googled this up.

10. Q: How can you tell the sex of a beaver?
A: Both sexes have a cloaca similar to a chicken, i.e. only one opening
for the digestive, urinary and reproductive systems. Since there are no
external sex organs, observation of enlarged nipples can be used to
identify a nursing female. Because the penis has a bone, X-rays or
palpatation are other common methods. Another way is to express the anal
glands of a tame, or immobilized animal. If the secretion is dark
(brownish), then it is a male. If light (clear or whitish), it is a female

Brian G

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Nov 26, 2009, 12:33:55 PM11/26/09
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From wdfw.wa.gov I found this information on sexing and aging beaver.

"Aging and Sexing
Sexing beaver is difficult since they do not have external sex organs
and they have a cloaca, which makes identification extra difficult.
Palpating for the baculum is the most common methods of sexing beaver.
Teats are evident in females only while they are nursing. Beaver can
be easily handled with a commercial catchpole and these allow you to
handle the beaver for sexing, ear-tagging, or attaching radio
transmitters.
There is no way to positively age live beaver. However, beaver can be
placed into one of four age classes (kit: 0-1 year, juvenile: 1-2
years, subadult: 2-3 years, adult: 3 years or more) based on weight,
total length, and tail width. Use at least two criteria to determine
age10.
Age of Beaver Adult Subadult
Juvenile
Weight ≥43lbs 30-43lbs 10-29lbs
Total Length ≥42" 38-42"
27.5-37.7"
Tail Length ≥11.5" 10.2-11.3" 7.1-10"
Tail Width ≥6.5" 5.0-6.2"
3.1-5.0"

Here is the link if you want to read everything they have about
beavers, which, with a quick review seems to be pretty detailed.
http://wdfw.wa.gov/hab/ahg/shrg/13-shrg_beaver_reintroduction.pdf

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