Pet mouse, very small, too young?

Question

My baby mouse   I got a small (hairless or short hair?)mouse from a reptile convention last weekend (Sat). The seller breeds them as pets but anyone that they don't sell becomes snake food. The mice looked pretty small, looked like they were maybe 3 weeks still in the weening stage. I was told they were just separated from their mothers and eating soft sweet potato. One was even smaller around 75% the size of the other ones but was really cute and crawled into my hand and cuddled up. I had to buy him. When I got home I continued feeding him soft foods and was continuing to ween him but within a day he was already eating solid food and drinking water just fine. My only worries is I have had him for a week and yet he still looks really small. His body is roughly the size of 3 nickels or just a bit larger than 2 quarters. His tail is a bit boney. Also he doesn't look like he is producing much heat as his body temp is low and he likes to spend most of the day in my hands, sleeves, or lap. He chirps a bit and is active and likes to explore as well, but I worry he is too small. Is he a runt? Will he be okay?

Answer
Dear Dash,

Sells them for snakes if they aren't bought as pets at 3 weeks? He doesn't give them a whole lot of time to charm the world into buying them :(.

Yes he is a runt, and will never be terribly large. I doubt he was three weeks. They can eat solid food at 2-1/2 weeks. It doesn't mean they are ready not to have their mom's milk. He also still needs the warmth of his mom and siblings to help him stay warm.

He needs a heating pad under part of his cage. He has to be able to escape the heat, so there should be a way to sleep in the warmth and away from it. The heating pad should be on low and there should be a thick (two thin) towel between the cage and the heating pad.

Not every three week old pup needs a heating pad, but there is a reason why runts die in the animal kingdom. They don't have everything they need to thrive like the bigger ones. They need coddling. I would also get him some kitten milk replacement (KMR) or soy infant formula and offer it to him in a little lid with crisp bread chunks in it. It goes bad quickly though-- don't leave it in the cage over an hour, especially not in a heated cage! And read the instructions to see how long it lasts. If you ever get a mouse that young again, start the milk right away.

He can also use some high energy foods to help him gain some bulk: avocado (no pit no peel), sunflower seeds, nuts (no raw peanuts), cheese, bacon, scrambled egg with butter.

He is exquisite. And if he spends that much time in your sleeves and hands, he will be the sweetest thing ever. He just needs the extra help.

As for chirping... I hope it is occasional. Because it if is more constant or near-constant, or sometimes constant, he might be sick and need antibiotics from the vet. Watch this carefully. A sick mouse also gets cool-- which is another reason to warm him up. You can save the life of a very sick mouse by keeping it warm.

Best to the little love,

Squeaks,

Natasha