Whiten and McGrew reply

We thank Kattmann for finding the elusive chimpanzee image used in designing the 1906 stamp that so intrigued us. This is a welcome demonstration of the power of international science, through the medium of Nature, to recover such an obscure item.

Kattmann suspects that the provenance of the 1887 image means we misinterpreted what the 1906 stamp itself portrays. Not necessarily. We recognized at the outset that the stamp design may have drawn on multiple sources of information, of which the image of the chimpanzee itself is only part. Indeed, closer inspection suggests that the 1906 stamp-designer knew more than the 1887 artist: the twig is shortened and no longer touches any object; the tree-hole and roots are replaced by what seems to be a mound; and the surface texture of the latter is different. The specificity of these changes suggests that the stamp design incorporates early knowledge of tool use in acquiring termites.

This would not have been the earliest report of tool use by chimpanzees, which we believe to be that concerning use of stone hammers to crack nuts in West Africa1. Our suggestion was rather that here we might be seeing the first realistic depiction of tool use.

Of course, a single stamp illustration cannot prove this point. We believe, rather, that the close match with what we now know of termite-digging may not be coincidental. Although Kattmann's rediscovery of the 1887 image certainly clears up some of the mystery, we remain keen to receive any information that tracks down the stamp's designer and the rationale for all he or she drew, for this might yet lead us to fuller and more informative early data on chimpanzee behaviour.