Is your house getting cooler? Perhaps the animal is going into hibernation. It could be sensing a cooler environment and react accordingly. Does it have a place to hide? If you think your animal is healthy (fatter) then you might just observe a bit longer. Check obvious things (mites and waste in the cage) and allow the temp to stay around 50 -60 for two months (you get a break from feeding!). Make sure your animal has water and a clean cage at all times. Good luck!

Dave
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One man with faith equals the majority.
Thomas Jefferson