Reptiles don't show many symptoms of anything, they are very stoic animals. It is likely you will just find him in eternal rest one day. Both of mine just passed away with no warning at all.
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A mans got to do what a mans got to do. A woman has to do what he can't.

Mom to:

1 little boy born 7/19/04
1 little girl born 2/2/06
2 male RES, born 1999
1 male lab mix, born 5/24/03
1 female calico cat, born 6/7/04