"Mngwa(translated as strange one) or the Nunda is a gigantic, ferocious, gray felid, said to stalk the East African country of Tanzania. Described as, "the size of a donkey," English contact with this animal first began in the 1900's. In 1938, an open-minded discussion of this animal appeared in the then-world-famous British scientific journal Discovery.
In Frank W. Lane's 1954 issue of Nature Parade, Patrick Bowen, a hunter who tracked the Mngwa at one time, remarked that the animal's tracks were like those of the leopard but much larger. The Mngwa was also described to have brindled fur that was visibly different from that of a leopard.
Lane believed that the nineteenth century reported attacks of the Chimiset, associated with the Nandi Bear, might actually have been attacks by the Mngwa.
The Mngwa was theorized by Bernard Heuvelmans to possibly be an abnormally colored specimen of a known species, or that it may even be a larger subspecies of the golden cat (Profelis aurata)."
anyone know anymore about this creature?
From the sketchy information available on it, I would guess that it is either a known species with a color mutation given mythical ferocity or just a plain myth. Finding a species of big cat with a brindled coat would be very odd indeed. I would guess that it (at least as I know how brindle looks) would not provide great camouflage. 
You just never know.....
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