My male mouse is gaining weight. Did I get a female? Separate them?

Hello and welcome to Petco Pet Education Center, formerly Petcoach. It is hard to know if she is fat or pregnant. If she has been in with a male in the past month she very well could be pregnant. The other female mouse might eat the babies, so I would separate the mice if she does have babies. Best of luck with your little ones!

It depends on how much he gained. Mice can range between 30 and 45 grams. If he weighs more, consider having him examined by your veterinarian to diagnose any medical causes, then consider adjusting his diet to maintain a healthier weight.

Thanks for reaching out about Sadie and including a photo. It appears as if the two new females where bonded and are bonded and ganging up on your first mouse. They can be aggressive but rarely do serious damage. But provide multiple hiding areas, food dishes, water dishes and area of rest. But if aggression continues, they might have to be separated. Good luck.

Your friend’s mice were probably just startled for some reason when you approached them today. I would recommend that you continue to engage and interact with them regularly to help gain their trust. The mice are in a relatively new environment and are probably very prone to stress. I would also recommend separating the pregnant mouse from the other two mice. Her pregnancy and birth can be very stressful and so anything you can do to help relieve her anxieties/stress would be good for her. I hope this helps. Thanks for using Petco Pet Education Center, formerly Petcoach. Best of luck.

Mice are prolific breeders. Gestation is about 3 weeks and they can reproduce throughout the year having 5-10 litters each year. Separating males from females is necessary to stop breeding. Females can breed at 3 weeks of age, so it is important to separate them prior to this age.

Thank you for your question. If this bump is only on one side of the abdomen I would be concerned about a tumor or an abscess (pocket of infection). With a pregnancy we would expect a symmetrical swelling of the belly. I would recommend your friend take the mouse to a vet who sees pocket pets for an examination to better determine the cause of the enlargement.

Thank you for using Petco Pet Education Center, formerly Petcoach! You are correct in planning for the arrival of the pups. I recommend separating the male as soon as you are sure that the female is pregnant, because females can get pregnant again very shortly after giving birth. It is important to keep the pups quiet and calm, to prevent the mother from eating them when stressed. You should also not touch the pups until they are about 14 days old. There are several types of nesting material available in pet stores, or you could use pieces of paperCut up into small strips. The pups should be separated from their mother when they are about 14 to 21 days old. At this point they should be able to eat normal adult mouse food. I hope this helps and I’m happy to answer any additional questions you may have!