Why does Gulliver ultimately leave the land of the Houyhnhnms?

Gulliver ultimately leaves the land of the Houyhnhnms because he is perceived as a Yahoo, which profoundly affects his identity and views about himself. The Houyhnhnms, rational and civilized horse-like beings, represent an ideal of virtue and rationality. They regard the Yahoos, a crude and savage species that resembles humanity but displays base behavior, with disdain. When the Houyhnhnms discover that Gulliver shares physical traits with the Yahoos, they can no longer see him as an equal or a noble being deserving of their trust and friendship. This perception leads to Gulliver feeling alienated and despondent, realizing that despite his intellect and aspirations, he is ultimately viewed as a lesser creature like the Yahoos. This experience of rejection and realization of his own humanity compels him to leave, as he cannot reconcile his own nature with the ideals he has witnessed among the Houyhnhnms.