Short-tailed Shrews and Late August

[Mike Ruzich]

This is the second deceased STS I have found in the past week. Based upon past observations, this seems to be an annual phenomenon. Shrews do no appear to have suffered any trauma, and they are always on a trail, pathway, or open area. This not to say there aren’t many more dead shrews in the undergrowth.

Also, late August appears to mark the onset of deer mouse invasion into the cabin. When the mouse droppings are found where one doesn’t want them, the traps come out in earnest, and I’ve trapped 8-9 mice in a day and a half. The ravens appreciate the snacks.

[Roger Powell]

Dear Mike and other Naturalists,

When tracking critters in snow, I have encountered shrews killed by
foxes.  The shr4ew and fox tracks meet, the shrew is left dead in the
snow with almost no sign of having been killed by a fox. Skinning the
shrew shows the wounds.  When finding dead shrews on unpaved roads in
the no-snow seasons, I have assumed that a number of them have been
killed by foxes, which often travel unpaved roads.  The moisture on the
shrew in your photo could be rain or could be fox saliva, were the shrew
really fresh.

    peace , , , , , ,

        rog . . . . . . .

Roger A Powell
Department of Applied Ecology
North Carolina State University
PO Box 918, Ely, Minnesota 55731

tel. - 218-235-8808
https://cals.ncsu.edu/applied-ecology/people/rpowell-2/

Husk at leve
mens du gør det.
Husk at elske
mens du tør det.
Piet Hein

On 24-Aug-23 08:16, Mike Ruzich wrote:
> This is the second deceased STS I have found in the past week. Based upon past observations, this seems to be an annual phenomenon. Shrews do no appear to have suffered any trauma, and they are always on a trail, pathway, or open area. This not to say there aren’t many more dead shrews in the undergrowth.
>
> Also, late August appears to mark the onset of deer mouse invasion into the cabin. When the mouse droppings are found where one doesn’t want them, the traps come out in earnest, and I’ve trapped 8-9 mice in a day and a half. The ravens appreciate the snacks.
>
>
>

> Sent from my iPhone
>

[Bill Hohengarten]

Interesting paragraph about the die-off!

In terms of foxes as predators, they would be the first thing that comes to mind for me, and certainly they travel the trails where dead shrews are found.  But if they kill them, why don't they eat them?

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[Tobi Mackey]

I was just thinking about this.  In past years , I took have found several shrews without any indication of trauma.   So far none this year.  Curious as to why I find these in August and September.

Do predators actually consume short tailed shrews?

Tobi

On Thu, Aug 24, 2023, 8:17 AM Mike Ruzich <michae...@att.net> wrote:

This is the second deceased STS I have found in the past week. Based upon past observations, this seems to be an annual phenomenon. Shrews do no appear to have suffered any trauma, and they are always on a trail, pathway, or open area. This not to say there aren’t many more dead shrews in the undergrowth.

Also, late August appears to mark the onset of deer mouse invasion into the cabin. When the mouse droppings are found where one doesn’t want them, the traps come out in earnest, and I’ve trapped 8-9 mice in a day and a half. The ravens appreciate the snacks.

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Sent from my iPhone

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[Roger Powell]

Dear Bill and other Naturalists,

Why do foxes and other predators not eat shrews?

One hypothesis is that shrews do not taste good.  Having never tried to eat one, I would not know.  Shrews do tend to have an interesting odor that is a bit astringent.  But, I have always figured that a hungry fox or coyote or bobcat would eat a shrew if hungry and that has been supported by scat analyses I have done.  Yes, foxes and coyotes do eat shrews, at least when they are hungry or mistake them for voles.  I had 1 coyote scat that had 6 compressed skeletons lined up in it head to tail.  Five of the skeletons were meadow voles but in the middle was a short-tailed shrew.  I wondered if the coyote caught and ate the shrew on purpose or if the coyote had been in a good vole spot and just happened to grab the shrew because it happened to be there with all the voles.

Another hypothesis is that predators avoid short-tailed shrews because of their venomous saliva.  On this hypothesis, again, I have figured that a hungry predator would eat a short-tailed shrew.  The little bit of venom in the saliva and salivary glands, enough to subdue big insect or another small mammal is small enough that I can not think that it would affect a fox or larger predator.  I have been bitten by short-tailed shrews and afterward felt as though I had drunk a gallon of coffee -- all jittery and such.  But, then again, my response could have been from adrenaline from having been bitten and wondering about the saliva.  My bet is -- adrenaline.

Nonetheless, foxes etc. do have a habit of killing but not eating shrews . . . and no one really knows why.  Biologists have generally figured that they have more important questions to answer.  But, who knows, answering this question just might lead to something really interesting.

Thazit.

    peace , , , , , ,

        rog . . . . . . . . .

Roger A Powell
Department of Applied Ecology
North Carolina State University
PO Box 918, Ely, Minnesota 55731

tel. - 218-235-8808
https://cals.ncsu.edu/applied-ecology/people/rpowell-2/

   Husk at leve
      mens du gør det.
   Husk at elske
      mens du tør det.
              Piet Hein

[Bill Hohengarten]

Until I read Roger’s reply I assumed shrews, as insectivores, only ate … um … insects (or at least invertebrates). But apparently they eat voles and maybe other small rodents too (as well as other shrews).  That suggests to me that foxes may kill them not as prey, but as competing predators. 

Bill

[Carl Karasti]

I've seen evidence of house cats catching and killing shrews – and never eating them or even any part of them.

The cats have never revealed why they consistently kill but never eat shrews.

But, come this time of the year, they sure kill a lot of them.

And there are always teeth marks from making the kills.

Carl Karasti

To view this discussion on the web visit https://groups.google.com/d/msgid/elyfieldnaturalists/de3c822b-c26c-66ea-4acd-04423fcde018%40ncsu.edu.

[Michael Joyce]

This is a topic that has come up before. I have also found many dead shrews (and star-nosed moles) this time of year along trails. Roger has given some nice information, so I won't rehash what he has shared, other than to add some additional context to predators eating shrews and one other factor that may contribute to dead shrews being found more frequently this time of year.  

Many predators do eat shrews, even those who also sometimes kill but don't eat them. I am unaware of any data on how many shrews killed by predators are eaten vs. discarded, but that would be interesting information to know. To echo Roger, we have also seen shrew remains in scats of martens, fishers, foxes, coyotes, and bobcats that we collected in Minnesota and analyzed for our research projects. Additionally, we recently got genetic barcoding data back from marten scats collected in northeastern Minnesota, and the scats contained DNA from 5 species of shrew: short-tailed, arctic, masked, smoky (!), and pygmy. We see shrew remains in marten scats we dissect more frequently than we see Peromyscus remains. I am not aware of any observations of martens discarding shrews they have killed, so perhaps they are not pertinent to this conversation as they may be less likely to discard shrews they have killed. But I figured it was still interesting information to share.  

Most of the shrews I have observed dead along trails this time of year are short-tailed shrews, but I have also found masked and other shrews dead along trails this time of year. I have also found dead masked shrews laying along cross country ski trails in the winter on 2 separate occasions. Other shrews are also thought to taste bad, but Blarina is the only shrew in Minnesota with venomous saliva. The fact that I (and most people I know) mostly find short-tailed shrews could suggest that the second hypothesis Roger brought up is more likely. But smaller shrews may also be harder to detect when present given their small size. 

Shrews and other small mammals are at their annual population maximum this time of year, which could be on additional factor contributing to higher observations of dead shrews this time of year. Additionally, carnivore populations at their annual population maximum this time of year, which could also contribute to more shrew-predator interactions and a higher frequency of discarded shrews right now. We collected a handful of scats from a pair of juvenile fishers this time last year and noted that relatively more of them had short-tailed shrew remains relative to fisher scats collected in other seasons. One of those scats also had a star-nosed mole in it. Roger can correct me if he knows better, but I am also unaware of observations of fishers killing and discarding shrews. 

Lastly, as Roger noted it isn't always apparent that there are puncture wounds in shrews killed by predators. On three separate occasions, I have collected shrews that did not appear to have any puncture wounds only to skin them and find that they did, in fact, have puncture wounds to indicate predators had killed them. 

Best,

Michael Joyce

Wildlife Ecologist

joyc...@d.umn.edu / office: (218) 788-2656

- -

Natural Resources Research Institute (NRRI)

University of Minnesota Duluth

5013 Miller Trunk Hwy, Duluth, MN 55811

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NRRI Mission: Deliver integrated research solutions that value our resources, environment and economy for a sustainable and resilient future.

Find out more: NRRI website / Facebook / Twitter / Instagram / YouTube / LinkedIn

[Michael Joyce]

Whoops, I guess this is the last thing I will share. To Bill's comments on thinking shrews only ate insects, one other item shrews eat is fungi, including mycorrhizal fungi. They don't eat as much as other small mammals (especially red-backed voles and squirrels), but they still play a role in dispersing spores of mycorrhizal fungi. 

We collected a handful of scats from a pair of juvenile fishers this time last year and noted that relatively more of them had short-tailed shrew remains relative to fisher scats collected in other seasons. One of those scats also had a star-nosed mole in it.

Michael Joyce

Wildlife Ecologist

joyc...@d.umn.edu / office: (218) 788-2656

- -

Natural Resources Research Institute (NRRI)

University of Minnesota Duluth

5013 Miller Trunk Hwy, Duluth, MN 55811

- -

NRRI Mission: Deliver integrated research solutions that value our resources, environment and economy for a sustainable and resilient future.

Find out more: NRRI website / Facebook / Twitter / Instagram / YouTube / LinkedIn

[Mike Ruzich]

Another one this morning.

Sent from my iPhone

On Aug 24, 2023, at 11:20 PM, 'Michael Joyce' via Ely Field Naturalists <elyfieldn...@googlegroups.com> wrote:

Whoops, I guess this is the last thing I will share. To Bill's comments on thinking shrews only ate insects, one other item shrews eat is fungi, including mycorrhizal fungi. They don't eat as much as other small mammals (especially red-backed voles and squirrels), but they still play a role in dispersing spores of mycorrhizal fungi. 

To view this discussion on the web visit https://groups.google.com/d/msgid/elyfieldnaturalists/11b7e5fc-ecd5-4201-be65-07cf7c2f9f6dn%40googlegroups.com.

[Mike Ruzich]

And yet another this afternoon.

Sent from my iPhone

On Aug 26, 2023, at 1:50 PM, Mike Ruzich <michae...@att.net> wrote:



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