Felidae carnivores, meaning they are dependent on nutrients in animal flesh for survival, and because of the large proportion of meat in their diet they are sometimes referred to as hypercarnivores. Of the 13 terrestrial families in the order Carnivora, they are the strictest carnivores. The Felidae comprises two subfamilies, the Pantherinae and the Felinae. The former includes the "Panthera" species tiger, lion, jaguar, leopard, snow leopard, and "Neofelis" species clouded leopard and Sunda clouded leopard. All the non-pantherine cats are part of the Felinae, which includes several genera and the majority of cat species. The first cats emerged during the
Pain in animals policy all allow for the conduct of what are often called “Category E” studies – experiments in which animals are expected to undergo significant pain or distress that will be left untreated because treatments for pain would be expected to interfere with the experiment.” Eleven countries have national classification systems of pain and suffering experienced by animals used in research: Australia, Canada, Finland, Germany, The Republic of Ireland, The Netherlands, New Zealand, Poland, Sweden, Switzerland, and the UK. The US also has a mandated national scientific animal-use classification system, but it is markedly different from other countries in that it