Tree dweller

Tree Dwellers (Commonthroat qgKqdqg /huff, early rising strengthening growl, huff, short high weak whine, huff, short low weak growl/ literally "forest yinrih") are a non-sapient species closely related to the yinrih. While humans often compare them to chimps, they're more closely related to the yinrih than chimps are to humans. It's better to think of them like early hominins. They're clever, can use simple tools, and have complex hierarchical social structures, but do not conduct rituals or possess language, which are the criteria the yinrih use to determine whether something is a sophont.

The Tree Dwellers and yinrih evolved from a single population of animals that lived in an equatorial rain forest river basin. Over time, the river widened, isolating the two populations. The northern population became the tree dwellers while the southern population became the yinrih. Both species are arboreal, but can also navigate on the ground well enough. The basin floods annually, and both species would spend the dry season on the ground and in trees, while remaining in the trees during the wet season.

To humans they look very similar to the yinrih. Their vocalizations even sound like yinrih speech, at least if you don't know Commonthroat or some other yinrih language. The only obvious visual difference is that Tree dwellers have more rounded ears (think the ears of a corgi vs the ears of a wolf or a German shepherd). Yinrih can smell the difference pretty easily, as well as spot other subtle visual cues in how they look and move.

The Tree Dwellers are similar enough to the yinrih that they're used for organ transplants and lab testing. In fact, before yinrih zoology was well developed, the yinrih considered themselves to be literally sapient tree dwellers, with the only difference being that yinrih had rational souls and tree dwellers had animal souls. A (relatively minor) religious controversy arises when it's discovered that they are in fact different species.

Some wealthy yinrih attempt to keep tree dwellers as pets. They're pretty cute as pups, but become aggressive when they mature. While they don't have the pound-for-pound strength advantage over yinrih that chimps have over humans, they're still more than capable of messing you up.

There's an urban legend that a group of Partisan scientists tried to teach a tree-dweller the concept of mortality. The outcome differs depending on who's telling the story.