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Meadow Vole Circles

Congratulations to “Maine Naturalist” and Stein for identifying not only that a Meadow Vole made the mystery tracks, but why they were circular! Thank you all for your comments, many of which were laughter-producing!    

More NC readers have witnessed this phenomenon than I would have imagined – the tracks were made by a Meadow Vole that had neurological problems which could have been caused by a brain parasite, brain tumor, inner ear infection, or a stroke. While the exact nature of an affected vole’s neurological impairment cannot be confirmed without the vole in hand, it is highly likely that a common brain parasite, Toxoplasma gondii, is responsible for a vole running in circles.

The snow-covered corn field where these tracks were located was just down the road from a dairy farm, where it’s likely cats could be found. This is relevant because cats pass this particular parasite on to rodents (and birds) who eat the cats’ feces.  The parasite goes to work on the brains of animals that have eaten cat feces, causing them to become disoriented (to the point where they lose their fear of cats).  Cats then eat the fearless rodents and the cycle continues.  When infected and disoriented, the rodents will often run in circles – hence, the unusual track pattern in the snow.

 T. gondii can infect humans, too, through consumption of under-cooked foods, contaminated drinking water, and through contact with cat feces.  This is why pregnant women are discouraged from tending kitty litter boxes, as the parasite can infect their unborn children.

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17 responses

  1. libbet cone

    Or… Maybe the voles are making an attempt at crop circles!!! Thank you again, And again and know my song to you. Libbet Cone Portland Maine >

    February 5, 2021 at 8:12 am

  2. Stein

    Thanks for filling in the large gaps of my guess, Mary. The back story is as interesting as the tracks themselves!

    February 5, 2021 at 8:14 am

  3. Alice

    Ikky parasites.

    February 5, 2021 at 8:20 am

  4. Val Cunningham

    Morning, Mary:
    Good to know the explanation for the circular patterns in the snow. Is it possible that other animals might also be passing on the parasite, in addition to cats? In my Minnesota backyard I see gray squirrels with severe neurological problems, and the vets at the local wildlife rehabilitation center feel this could be caused by a parasite that reaches their brains. Raccoons are the carriers although they don’t seem to be affected, but pass it along in their feces.

    February 5, 2021 at 9:18 am

    • I honestly don’t know, Val. I have seen the circling behavior in two different porcupines as well and been told it’s a brain parasite, but not sure which one or how it’s acquired!

      February 5, 2021 at 11:46 am

    • Hi Pam,
      I wish I had the time to research the answers to your questions! I believe cats are the only known hosts in which the parasite may undergo sexual reproduction so I think (?) that means that as least as far as Taxoplasmosis goes, the squirrels might have a different brain parasite? Sorry my knowledge is limited!

      February 5, 2021 at 11:54 am

    • HI again, Val. I do know that humans can carry this parasite for years, and not show any symptoms, so perhaps that is true for all creatures? Also, the parasite only reproduces in cats, so I think the squirrels must have another parasite…

      February 5, 2021 at 11:56 am

  5. Betsy stewart

    Thanks Mary – for spreading the word about toxoplasmosis. I ate undercooked beef and ended up with the parasite and lost the central vision of one eye. I can read and drive etc – so Tis not too horrid.

    February 5, 2021 at 9:46 am

    • Oh, Betsy, that’s horrible. So sorry!

      February 5, 2021 at 11:48 am

  6. Sharon Walker

    Wow. Really interesting

    Sent from my iPhone


    February 5, 2021 at 10:07 am

  7. hellomolly

    Wow, fascinating! But poor vole!

    February 5, 2021 at 11:01 am

  8. The photo, with its beautiful pattern, now seems sad to me.

    February 5, 2021 at 11:08 am

  9. Pam Bullock

    Hi Mary—

    Fascinating! A beautiful trail for a sad demise. I assume the Toxoplasma gondii would eventually kill the rodent if a cat or other prey did not get it? How long does a vole live in circles before it dies? In other words, are those tracks the last day of that animals life, or might it have carried on for days or weeks that way — providing it doesn’t become prey first? Would a bird of prey become infected if it were to eat the rodent?

    Just Curious for more,



    February 5, 2021 at 11:31 am

  10. Shirley Weinberg

    THANK YOU !! What an amazing story.


    February 5, 2021 at 7:44 pm

  11. Jack Cole Sue Calhoun

    Can Toxoplasma gondii affect dogs? My dog loves to find and eat cat feces (ugh)

    February 6, 2021 at 4:01 pm

  12. Maine Naturalist

    Hi Mary, thank you for the shout out for “solving” the mystery photo! I’m so glad to have finally gotten one right!

    I filmed a healthy vole this weekend, running all around on the snow and searching for its subnivian trail entrance…

    February 8, 2021 at 11:03 am

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