Very interesting. That is essentially a story of Natural Selection (i.e., Survival of the Fittest). The story is very similar to the Kiko Goats of New Zealand, another island species with exceptional hardiness. In fact, one of the knocks against true dairy goats is 1) they eat twice as much as "normal" goats to facilitate the lactation and 2) their udders hang so low to the ground they can't really be let loose in heavy plant/briar growth, because it will tear their huge titties to pieces.

This demonstrates the pros and cons of natural evolution versus human-selective breeding ...

Jack