We used to only have the cute, little grey deer mice at the cottage. But I just found five brown ones in the sleeping bag in your room. Aren’t the brown ones “city mice”?—Jackie’s Mom, via email
Hey, Mom! Don’t hate: all mice are cute. Just not when they’re inside a sleeping bag on a bed where someone is expected to sleep in the future. Or dead, as in the photo that you emailed Cottage Q&A. The image was too grim to print in the pages of this magazine, but not too grim to send to some experts. The verdict? Both the grey mouse and the brown mouse in the image are deer mice (Peromyscus maniculatus).
When it comes to mouse ID, “Colour doesn’t really mean a whole lot,” says Lauralee Proudfoot of Cottage Country Pest Control near Midland, Ont. Deer mouse fur varies from grey to brown; the species’ common name stems from the fact that their colour is similar to that of a deer. The one (colour) feature that distinguishes deer mice from house mice (Mus musculus) is their white underparts—look at the bellies and undersides of the tails of the mice in the photo.
Tom Sullivan, a professor emeritus in applied biology at UBC, ID’d the grey mouse in the photo as a juvenile and the brown one as an adult—that could explain why their body shapes are slightly different. We don’t know why you used to only catch grey mice. Maybe there are just more deer mice with brown fur in the local population now.
See you at the cottage, Mom! Please launder that sleeping bag.
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This article was originally published in the May 2022 issue of Cottage Life magazine.