Shrew-eating Trout

Rainbow trout with a stomach full of shrews in Togiak National Wildife Refuge, Alaska: http://blog.nature.org/science/2013/09/03/shrew-eating-trout/

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5 Comments on “Shrew-eating Trout”

  1. Jon Hall Says:

    Matt, fascinating story. The voles I could understand but the shrews not. You’d imagine these would have to be water shrews but they don’t look like they are from the picture. Do you know – or can you find out – what species they are? cheers Jon

  2. mattinidaho Says:

    Hi Jon
    There are no records of water shrews at Togiak according to US Fish & Wildlife Service surveys. There are 4 species found there: common, tundra, pygmy and Alaska tiny.

    Here is a note I received from Togiak education specialist Terry Fuller about trout and shrews:

    “I spoke with our supervisory wildlife biologist, Pat Walsh, and he was uncertain on the exact species but the two best bets are tundra shrew and common shrew; they are far and away the two most common species found on the refuge. He said that without a careful firsthand examination it was impossible to tell, but that tundra shrews or common shrews were very likely. He also said that for whatever reason shrews get targeted far more than other small mammals. He said shrews are frequently found in fish on the refuge, far more so than voles (for example) even though voles are much more abundant than shrews. He said they don’t have an explanation for why that would be but it certainly the case. Both inhabit the same places and both wind up swimming from time to time but it seems to be the shrews that fish tee off on.”

    Togiak looks like a cool place; it has walruses–and a lot of other mammals (and fish!).

  3. Jon Hall Says:

    This is really interesting… the number in the stomach alone. Any idea how long they would stay in there before decomposing? I spoke to Fiona Reid (author of the Mammals of the USA) about this and she thought they might well be Common Shrews if they were one of the 4 on the list, but also that this must mean S. cinereus must swim a lot more than we realise. Unless the Trout are making like the Orcas of Patagonia and grabbing them on the beach. Yes I’d love to go to Togiak! jon

  4. mattinidaho Says:

    Hi Jon and Fiona,
    Here’s more from Terry Fuller of Togiak…an interesting theory from a fishing lodge:

    “I have another shrew/trout tidbit for you. My supervisor was speaking to the manager of one of the bigger lodges in our area. He used to guide on the Kanektok. I guess he saw the photo and said that he and the other guides use to study the small mammals, trying to get a feel for the why of it all with regards to small mammals and trout. The voles apparently swim very well but the shrews do not swim well at all. He said the shrews flounder and eventually succumb in many cases. He thinks that many of the shrews that are eaten are taken after they drown. Nothing scientific here, but supposedly this was witnessed between 50 and 100 times. “

  5. vdinets Says:

    Shrews have negative buoyancy and drown easily. I think that’s what allowed so many aquatic shrews to evolve: they have no problem diving, even with a lot of air trapped in the fir. Siberian taimen (giant relatives of salmon) also often have shrews in their stomachs.


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