i am about to start a phd but i am wondering whether i got the right subject. What career could i do with a phd in visual ecology, the study of visual signals and communication etc...

You may have thought of this question a little late. It's a very good question to ask at your interview. PhD's can lead to a number of subject specific careers, including some you may not have thought of. The people in your new lab/department will be full of cynical career options, but there'll be some realistic ones there too.