I have spent an awful lot of time on safari in Tsavo over the years, it is a truly magical place.
I rather suspect that the lioness in the engraving is, in fact, a lion. Tsavo lions are without mane. My assumption is based on the fact that the most famous Lions from the area are the two man-eaters that were hunted, shot and killed by Col. J. H. Patterson during the building of the Kenya-Uganda railway, which would tie in neatly with the human limb being portrayed?
It is a fascinating story, recounted excellently in the book by Patterson entitled "The Man Eaters of Tsavo" or, if you prefer it visually, "The Ghost and the Darkness" starring Val Kilmer as Patterson. The film I can take or leave, but the book is definitely worth a read...