The animal faced competition from whale-eating cetaceans, such as Livyatan and other macroraptorial sperm whales, and smaller ancestral killer whales such as Orcinus citoniensis. As the shark preferred warmer waters, it is thought that oceanic cooling associated with the onset of the ice ages, coupled with the lowering of sea levels and resulting loss of suitable nursery areas, may have also contributed to its decline. A reduction in the diversity of baleen whales and a shift in their distribution toward polar regions may have reduced megalodon's primary food source. More recently, evidence has come forward that competition from the modern great white shark may have also contributed to the extinction of megalodon, coupled with range fragmentation resulting in a gradual, asynchronous extinction as a result of cooling oceans around 3. 6-4 million years ago, far earlier than previously assumed. The extinction of the shark appeared to affect other animals; for example, the size of baleen whales increased significantly after the shark had disappeared.