I've posted a new blog on my website:
Tortoises Through the Eyes of a Biologist: What Can Wild Tortoises Tell Us About Our Pets? Part I - Evolutionary History
Over a four-part series of blogs, I discuss aspects of the biology of wild tortoises – including evolutionary history, life history...
My male erosa does this, too (rubbing his gular against objects). My guess is he's 'blowing off steam' so to speak, perhaps because his blood testosterone levels are high and he's looking for a fight with another male.