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#7403 - 03/22/08 08:21 AM Re: Question: An Otter's Favorite Diet
Hal Online   content
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Registered: 07/17/00
Posts: 10080
Loc: Blue Creek, Ohio, USA
You're the second person on this thread who has mentioned otter eating beaver. Yet I can find no documentation.

Can either of you fellows cite research or any study that shows beaver found in the stomach contents of otter?

There is no shortage of beaver in Missouri, yet of those 443 otter necropised there not even one had eaten a beaver.

I find this curious.

Hal
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#7404 - 03/22/08 12:16 PM Re: Question: An Otter's Favorite Diet
northern trapper Offline
Member

Registered: 10/05/00
Posts: 274
Loc: Wood Buffalo, Alberta, Canada
This is pretty common knowledge up here. I'm not sure I have the time to hunt up a study however there is no shortage of written material in government publications.

The predatory nature of northern otters likely has to do with prey availability. The otters in winter spend as much time above as below the ice. Fish and clams are not always around in this habitat so the beavers which number in the thousands on most trap lines are the most prevelant prey species.

Fish is a much easier target than beavers for an otter, as the otter has to fight the adults to get at the yearlings and kits...so if there is an abundance of fish in a habitat full of beavers I have no doubt the otter will choose fish.

A good analogy is the mink/muskrat relationship...up here the mink is the dominant predator of the muskrat, and the hunting technique is very similar to that of otters and beavers

When the otters hit a beaver colony on a drainage they chew through the ice below a dam and hunt the dens and lodges entering the runs under the ice.

I have seen otters nail young beavers in the spring/summer on several occations.

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#7405 - 03/22/08 03:26 PM Re: Question: An Otter's Favorite Diet
Hal Online   content
Moderator

Registered: 07/17/00
Posts: 10080
Loc: Blue Creek, Ohio, USA
That's interesting. If beaver were high on the otter's food list in the south, they would probably be protected with all the problems nuisance beaver have created.

I've caught a lot of otter with beaver bites on them too. But most of the time these bites are on the otter's tail or butt. I figured the otter just made the mistake of entering an active beaver den/lodge, and got bit on the butt as they turned to escape. I don't think I've ever seen one bit on the head or the shoulders, as if they had been fighting.

But again these are all southern otter. There's not much "under ice" activity, because there's not much ice.

smile -- Hal
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#7406 - 03/23/08 01:26 AM Re: Question: An Otter's Favorite Diet
Dusty Offline
Member+

Registered: 12/15/00
Posts: 420
Loc: North Pole, Alaska, USA
Interesting. I've seen plenty of places where otters have used beaver dams or lodges to get in or out of the ice. I've followed their trails for miles, found my share of "toilets," and even manged to catch a few. I've also caught a few otter in under-ice beaver sets. I've never seen any evidence of otter targeting beaver, and frankly, the possibility never really occurred to me.

I managed to dig up one paper that has actual data (Reid, D. G., T. E. Code, A. C. H. Reid, and S. M. Herrero. 1994. Food habits of the
river otter in a boreal ecosystem. Can. J. Zool. 72:1306-1313.). They found 27 beaver-bits in 1191 turds. Another (unpublished and unreviewed) paper (Heidi Hansen, University of Wyoming, 2003) said "it is commonly contended by trappers in Alberta that otters are significant predators
of beavers," but offered no evidence. I also found in a USFWS bulletin written by a forester (or the technician thereof), and claiming no particular credence that I can identify, "Northern river otters may kill young beavers found alone in a lodge."

So, it looks like there are data to support otters eating at least some beaver, but 2% of a reasonable sample of otters having beaver in their turds doesn't evoke the words "favorite" or "major predators" to me. Otters are fairly frequent visitors to moose kills. I'd not be surprised to find moose hair in >2% of the otters in some areas I trap, but that's not great evidence that otters are killing moose either! There's also lots of acknowledged conjecture, which generally says nothing meaningful about actual behavior.

I'd think I'd have found an otter-killed beaver or two in all the time I've spent flying around following otters. I find plenty of fish-bits that they've pulled up on the ice, especially in the spring when they're spending more time on top. Assuming they are killing beaver, what are they doing with them?

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#7407 - 03/23/08 10:36 AM Re: Question: An Otter's Favorite Diet
Top Jimmy Offline
Member

Registered: 09/10/06
Posts: 71
Loc: Alaska
Dusty,

I find that interesting. We have had Otter eat beaver out of under ice sets on the flats, so maybe they tend to scavange when the opportunity presents itself. Though I know of one instance where we are pretty sure that they wiped out a beaver hut, but couldn't verify it for sure as we coudln't go back come spring time to see.

We set up a hut with an under ice set and caught a beaver. However, the otters found the set and were going in and out of our hole. They spent some time there as they kept the hole open for the entire week and were in and out and playing on the hut and around the area. They ate out the entire inside of the beaver and around the head and tail area, pretty much leaving a bag of bones. However, after that, we didn't catch another beaver and that hut is now dead for the past two seasons. We are pretty sure they went in there and killed off the remaining beaver.

-TJ

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#27009 - 01/07/20 10:54 AM Re: Question: An Otter's Favorite Diet [Re: redsnow]
Archive Offline


Registered: 03/12/03
Posts: 1486
Dated for search.

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