Can I replace my right headphone if my dog ate it?

This is a user helping users with tech questions, we are not apple and apple do not read your posts here

their warranty maybe apart of if you have some apple care++ model does not cover other stuff than production defects discovered after purchase not external damaged products like dogs

Legal - Hardware Warranties - Apple

they do sell replacements though Headphones & Speakers - iPhone Accessories - Apple

Yes, but you will have to pay the full cost for the replacement.