In the last few days Winnie has become increasingly reluctant to go for a walk. There is a lovely country park across the road from my housing estate (max 1/4 mile away) but 2 days ago she just nosed around in the trees for a while and then wanted to go home. Yesterday I managed to encourage her to walk around, although she kept turning back and looking at me to follow, and then dragging herself along behind me wearing a hang dog expression and lying down if I stopped. Today she started enthusiastically from my house but by half way to the park she was already dragging behind on the lead. When we were safely in the park I took the lead off and called her to follow as usual. To my dismay she turned around and walked all the way home without a backward glance....past entrances to an estate where she usually hunts for cats, straight over a road, and right to the side gate of my house - ignoring the scents of my neighbours cats (and, of course, ignoring her screaming and whistling and panicing owner following behind!). She seems to lack energy and enthusiasm and just sleeps all day. She is eating well, and is showing no other sign of illness or distress.
Should I be worried (I am already!). Any ideas what could be wrong? She is 8-9 years old but is usually quite sprightly.