While a hiding ball is a happy ball they should not hide without ever coming out. Elliot is acting normal. Mine will usually stay put for two days after feeding and then return to coming out a bit each night. It is never that long but it is regular. I work nights so I'm up nights. I think this has allowed me to see my snakes act more natural than you day walkers. I could easily see how it would seem your bp never moves if I only observed it during the day.

Now if he stays active day and night for extended periods of time you need to check the cage numbers, but a nightly crawl is nothing to worry about.

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Do you know his weight?

It is always hard to judge size on a video but it kinda looks like one mouse would be fine. What feeding regiment are you trying?

Mouse weight?
How often?