How does Pi prove to be " the next goat"?

From the text:

Ravi was right. Truly I was to be the next goat. I had a wet, trembling, half-drowned, heaving and coughing three-year-old adult Bengal tiger in my lifeboat. Richard Parker rose unsteadily to his feet on the tarpaulin, eyes blazing as they met mine, ears laid tight to his head, all weapons drawn. His head was the size and colour
of the lifebuoy, with teeth.

I turned around, stepped over the zebra and threw myself overboard.