What kind of meat is that?

Or nutria (coypu).

Agreed. And if all I knew was that it was gyro meat served at a Greek restaurant in Germany, my first guess would have been pork. But if he said it tasted like beef, why doubt him?

I once was served pork gravy with chicken. After I got over the “huh, what on earth is this?” response (since I’d been expected chicken gravy, of course) it was pretty obvious it was pork gravy. Pork and beef taste pretty different, too.