Uhm no! straight from Wiki
Melanistic cougars
There are no authenticated cases of truly melanistic cougars. None have ever been photographed or shot in the wild and none have been bred. There is wide consensus among breeders and biologists that the animal does not exist and is a cryptid.
Cryptid, is a pseudoscience focused on the search for animals which are considered to be legendary or otherwise nonexistent by mainstream biology. This includes looking for living examples of animals which are considered to be extinct, such as dinosaurs; animals whose existence lacks empirical support but which appear in myths, legends, or undocumented sightings, such as Bigfoot and el Chupacabra;[1] and wild animals dramatically outside of their normal geographic ranges, such as phantom cats.