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Mice Missing Ears
Mice Missing Ears  
I recently went to a pet store and all the mice were missing their ears with crusted blood around the area. The store owner claimed the mice did this to each other. I doubt this is true, as all the mice had these wounds and were otherwise uninjured (although one of the mice had an ugly red cut on the top of its head). Would mice do this specific injury to their cage mates?

Hi Lucy,

That... Is absolutely horrifying.  I would find another pet store immediately, and consider letting your local animal control officers know that the owner feels keeping these mice this way and in this condition is in any way appropriate.

Without a consultation from a veterinarian, I can only speculate as to the cause, but here are a few possibilities going through my mind:

- If the mice are all male, this may indeed be the way they've chosen to fight. In a one-on-one situation they may fight to the death, but when there are several crowded mice, they don't always get a chance to pick on one mouse in particular. I have NEVER seen mice chew off each other's ears... And stop there.  I have, however, seen mice bite at another's ears when fighting.

- If this was indeed done to each other, it is likely learned, and should NOT have new mice brought in or sold to other colonies where this habit could be spread.

- Disease/Parasites. Things like mites, lice, allergies, ear infections, and other irritants frequently cause itchiness around the ears, face, and shoulders.  A heavy mite infestation could cause such severe itching that they could, indeed, scratch their ears off, leaving scabs and irritated, weeping skin.  This isn't usually confined to the ears, but I would consider this a HUGE and immediate reason for the owner to get at least one of these animals to a veterinarian for a skin scrape to identify or rule out parasites causing them to do this to themselves.  These are obviously not healthy, and selling them would be unethical at best, and a danger to the lives of other rodents and reptiles at worst.

- Neurological disorders.  If these mice came from the same line, and if that line happened to be prone to self-harming ticks when distressed, then keeping them together in this manner could absolutely bring out self-destructive habits.  There is evidence of some mice hurting themselves when stressed if a neurological problem is at play, much like when people pick at their skin or hair when stressed, but obviously much more severe in this case.

Lucy, there is no way for me to know exactly what the cause is, but it's clear to me from this photo and your description that something is VERY wrong in this enclosure.  If the owner is friendly, please encourage an immediate trip to a veterinarian, and if they are not willing to listen, do NOT be afraid to report poor conditions to your local authorities.  I can think of absolutely no reason in which twenty mice or more as you mentioned should live with scabbed, crusted, missing ears with no cause identified and still available for sale!

If you have any other questions or need help figuring out how to speak politely with the owner, please let me know and I will do what I can to help.



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I can answer questions regarding mice as pets, mouse behavior, color and coat genetics, breeding techniques, and general health questions. I can help with caging and setup, nutrition, social issues, and what to do in most mouse emergencies (such as unplanned litters, injuries, fighting, etc.). I can also assist with questions pertaining to orphaned mouse pups, weaning litters, and questions of mating and birthing. I cannot answer questions about exotic or wild varieties of mice such as spiny or pygmy mice. *****FOR EMERGENCIES, anything requiring immediate medical intervention, PLEASE take your mouse to a professional veterinarian or wildlife rehabilitator who works with mice as soon as possible! IMPORTANT RESOURCES: Raising Orphaned Mice: Orphaned Mice Videos: Natasha's Your First Mouse: General Mouse Help: Mouse Info and Exotic Breeds:


I have enjoyed the companionship of mice nonstop since 2004, and spent a year caring for them in a lab where I learned a great deal about their breeding, social needs, and health. I spent a few years breeding them, specifically working with albinos, marked mice, angora mice, and satins. My education never stopped - I am learning something new every day from current and well-established research thanks to the wonderful folks at the Jackson Laboratory, as well as from my wonderful mousey friends online. I also love learning from my terrific questioners here on AllExperts - you folks keep my passion for these amazing animals alive and well!

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