1. Restlessness: Maggie, the 10-year-old calico cat, was always a quiet girl. She preferred to spend most of the day sleeping in a wicker basket. So when Maggie began exploring the house more, particularly at night, her family was thrilled to see her becoming more active. Maggie would pace through the house, checking every room and sometimes let out a single meow. Turns out, Maggie was suffering from a brain tumor that was giving her severe headaches. The pacing was her response to the pain. What looked like a wonderful new sense of exploration, was actually the manifestation of severe illness. Restlessness can be a firm indicator of pain or anxiety.