You asked, "Does anyone know where the Bible talks
about animals becoming more ferocious in the Last
Days?"  I know of one such verse in Revelation:
 
Revelation 6:8
I looked, and there before me was a pale horse! Its
rider was named Death, and Hades was following close
behind him. They were given power over a fourth of the
earth to kill by sword, famine and plague, and by the
wild beasts of the earth.