Fig. 4.

The transfer of saliva from tongue to fur. (A) Cat fur forms clumps when wetted. (B) Schematic of clumped wetted hairs, which have a local reduction in porosity. (C) A single groom of the cat tongue as visualized by blue food dye transferred from the tongue to the fur. The length of groom corresponds to the grooming length $L_{\text{groom}}$ in domestic cats. (D) A groom of the cat tongue, this time with blue dye wicked into a single cavo papillae. (E) The relationship between the volume of water transferred and the velocity of the groom. The vertical gray bar indicates the grooming speed of a domestic cat. The dashed line shows the predictions of our mathematical model (see SI Appendix), using a wetted fur porosity of $\epsilon =0.093$.