They are actually Leopards, Jaguars and Pumas that are born with a mutant gene, resulting in them turning black.
With Leopards and Jaguars, you can still see their spots.
In Bagheera's case, he's a Leopard, since The Jungle Book originally takes place in India. In Panthy's (or is it Panty?) case, she's probably a Puma, so maybe that Puma in Dagnino's gang is her partner