So, er, about this shadow thing...

How does one tell the difference between "my cat is unique" and "my cat has a problem"?

Ender spent most of the early morning and evening today chasing shadows, staring at shadows, chattering away at shadows. He behaved normally during the middle of the day (mid-day is a time of rest for Ender). He can be distracted from the shadows, but he goes back to them. He seems happy, but is this a problem? Will it become a larger problem? Short of turning off all the lights and/or releasing live mice in the house, is there anything we can do? He has lots of toys, we play with him, he has his own cat and dog, a birdfeeder to watch, 3 cat posts, etc.

eta -- It's 11 at night, and Ender is making the bedroom door swing back and forth as he attacks Orion's shadow. He will get tired eventually, won't he?