Double check your Genesis. It rained for 40 days and nights, then the Ark floated for 5 months. They entered on the seventeeth day of second month, and it landed on Mount Ararat on the seventeenth day of the seventh month.
As to what the animals ate, well, the Bible says that Noah and his three sons and their families all entered the Ark. It didn't say they all got off at the end.
LOL, 100,000 animals enter, only 100 leave. The ultimate cage match.