She has started trying to bury *everything* in sight.

In the last few minutes she has tried to bury: a package of envelopes;
a videocassette; a folded paper bag; a stack of bowls; dubbing cables; a
pillow; one of her sisal scratchers; a plastic bag containing a box of
pasta. I've been watching, dumbfounded. As I type this message she is
ripping up an area rug while trying to bury some invisible thing. WHY???

Should I be calling the emergency vet?