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Mice/Moise died


QUESTION: I was on vacation and I had a neighbor taking care of my pets and I told them to feed the mice a certain amount of mouse food and we usually feed the mice lettuce and other vegetables and pumpkin seeds and assorted nuts but when I got back from vacation the mouse was huge! The mouse used to be the smaller one in the cage but she was twice the size she once was. Even her fur looks a little different it almost looks like it changed color a little bit. I'm sure the mouse is not pregnant but I just want to know how I can get the mouses weight down

ANSWER: Hi Andrew,

You didn't say how old your mice were, but most mice are sold very young, so after having them for a couple of months it is not uncommon for them to gain a little weight.  Certain genetics, such as yellow/orange mice, also contribute to obesity.

Mice should never have their food restricted - all mice in the cage should have free access to food around the clock.  The best way to control nutrition is to be sure the food offered is the healthiest possible.  High levels of fat or protein (such as using frequent seeds or nuts) can pack on the weight, cause greasy coats, and contribute to health problems.  The best diet is a commercial one labeled specifically for mice, particularly lab blocks or pellets rather than seed-only mixes.  These kinds of diets are carefully formulated to include all the trace vitamins and minerals needed by mice, and it's extremely difficult to replicate at home.  This commercial feed should be made available 24 hours a day, with treats such as seeds, fruits, veggies, nuts, millet, cheerios, etc. being offered only now and then (2-3 times a week in small portions).

Hopefully this helps bring her weight down to something more reasonable, but at the very least it will keep her from gaining more or causing herself health problems in the future.  If you have any other questions please let me know!


---------- FOLLOW-UP ----------

QUESTION: I did what you said about feeding the mice the mouse diet and when I got home from school today the other female mouse I had in the cage died. She was smaller yesterday but when I found her dead she was much fatter. I think tonight I'm going to the pet store to get another mouse or two because the mice are social. Please help me try to find out what happened.


First of all, I am so sorry for your loss. Keep in mind that your other mouse will be grieving, too, and may need extra attention from you for a little while.

Mice do not die from obesity, and since it came on so quickly, is it possible she could have developed a tumor or abscess? The only way to find out why she passed would be to talk to your veterinarian about doing a necropsy and possibly a histopathology (a necropsy is the animal version of an autopsy). If you want to do this, you will need to refrigerate her body immediately, as deceased pets decay quickly, making it harder to determine the cause of death.

If you would like to get more mice, that is great! However since the other female mouse will be grieving right now, you might need to wait a short while before introducing anyone new. The best plan would be to pick out new females and then keep them in a separate cage in a separate area for three weeks. This is called quarantining, and not only gives her time to adjust, but also makes sure the new mice do not bring home any diseases from the pet shop and put her at risk of getting sick.

I'm sorry again to hear about her passing. Best wishes to you and your other pet.



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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!

East Coast Mouse Association - expired, American Fancy Rat and Mouse Association - expired

Partial University for a B.S. in Microbiology, Partial University for a 2-year degree in Veterinary Technology (RVT cert), C.E. classes in pathogens, aseptic technique, genetics, and applications

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