found a couple of other studies recently done on the intelligence of red-footed tortoises.

"Social learning in a non-social reptile (Geochelone carbonaria)," by the same folks at the university of vienna who did the gaze-following study:

http://www.ncbi.nlm.nih.gov/pubmed/20356886

"Visual and response-based navigation in the tortoise (Geochelone carbonaria)" from the university of york:

http://www.ncbi.nlm.nih.gov/pubmed/19466467

in case anyoen wants to do any further reading.