Some tropical animals can survive in cooler climates. And some animals that now live in Polar Regions can also survive in warmer temperatures. Today marsupials live mainly in Australia. Penguins live in the Southern Hemisphere, while polar bears live in the north. Kangaroos did not have to hop all the way from Australia to get on the ark.
Today kangaroos only live in Australia.
But prior to the flood, kangaroos and other animals most likely lived near Noah s home. Prior to the flood, the earth may have been one large landmass. Australia did not exist in its present location. Our present continents are shaped as a result of re-disposition of flood sediments, and receding flood waters. Years later, the glaciers started to melt and the water level rose.