Animals multiplied and thrived in the warm forests, forming new forms such as herbivores, carnivores, and omnivores. However, under the high temperatures of the PETM period, some animals began to shrink in size, which is similar to the phenomenon biologists are finding in today's mammals. For example, in cold climates, moose generally weigh about 80 pounds (approximately 36.28 kilograms) more than their southern counterparts.
