Acadia - this is the first render I've actually noticed it on. As it happens, I was playing around trying (and failing) to get some decent reflections on the eyes and some life into the whites, so bagginsbill's pointer looks like it hits the mark. There must be a tutorial on setting up eyes somewhere.. better go looking this evening.

bantha - I'm using P7.

bagginsbill - yup, that looks like it might be the problem... I'll give it a try and report back.

Thanks everyone for your help!

"If I were a shadow, I know I wouldn't like to be half of what I should be."
Mr Otsuka, the old black tomcat in Kafka on the Shore (Haruki Murakami)