He had often seen herds of quaggas, and was in no way curious about them.

But his attention was drawn to this herd, from his noticing, as they passed him, that four of them had their tails docked short; and from this circumstance, he recognised them as the four that had been caught in the pit-trap and afterwards set free.

Swartboy, for some purpose of his own, had cut off the hair before letting them go.
Hendrik had no doubt it was they, and that the herd was the same that used to frequent the vley, but that on account of the ill-treatment they had met with, had never since shown themselves in the neighbourhood.
Now these circumstances coming into Hendrik's mind at the moment, led him to regard the quaggas with a certain feeling of curiosity.

The sudden fright which the animals took on seeing him, and the comic appearance of the four with the stumped tails, rather inclined Hendrik towards merriment, and he laughed as he galloped along.
As the quaggas went off in the same direction which the eland had taken, of course Hendrik's road and theirs lay so far together; and on galloped he at their heels.

He was curious to try the point--much disputed in regard to horses--how far a mounted quagga would be able to cope with an unmounted one.