I couldn't find a mention of this in the IEEE article, but a story on NPR on this topic this morning specifically mentioned that the penguins "sang to it and se

I couldn't find a mention of this in the IEEE article, but a story on NPR on this topic this morning specifically mentioned that the penguins "sang to it and seemed disappointed that the rover wouldn't peep."[1] So, yes, it looks like the penguins did hit a level where they might have been (at least) confused about what was happening. [1]: http://www.npr.org/2014/11/03/361069792/scientists-find-sneaky-way-to-check-penguins-vital-signs http://www.npr.org/2014/11/03/361069792/scientists-find-snea...