Nature of the Beast — Adam Mansbach

An alien race of religious extremists plan to honor their deity
through the ritualistic annihilation of our planet. The only man who
knows this is Milan Marlowe, an unstoppable media baron who sees
opportunity everywhere.

Earth's only move is to engage the invaders according to their
holy law and issue The Challenge of the Heretic -- a winner-take-all
gladiator battle for our right to exist. Marlowe launches Beast Wars,
a televised interspecies tournament designed to select Earth's
mightiest champion. On a decadent private island, sharks, lions,
gorillas, and polar bears square off to the delight of screaming
fans oblivious to the sky-high stakes.

Enter Bruno Bolo -- single father, blues belter, and alligator wrestler
from the swamps of Florida. Beset by personal demons, corporatized
killer sharks, Yeats-quoting pit fighters, and looming alien eradicators,
Bruno will emerge as our desperate planet's final hope.