Transfigurations by Michael Bishop

In a clearing of the great forest of the planet Bosk Veld, a strange, ape-like species of alien, the Asadi, act out their almost-incomprehensible rituals, rainbow eyes flashing, spinning like pinwheels.Egon Chaney, in his anthropological study, "Death and Designation Among the Asadi" has shown how their life-style has apparently degenerated from a level of complex technological sophistication and devolved to a primal simplicity. Long after his disappearance in the forest, his daughter, Elegy Cather, comes to Bosk Veld to carry on his studies of the Asadi where he left off. With her is an intelligent ape, Kretzoi, physically adapted to resemble the aliens.Together with Thomas Benedict, Chaney's old partner, Elegy begins to unravel the enigma of the Asadi. As Kretzoi insinuates himself into their rituals, so we are drawn into what is perhaps the most convincing portrayal of the alien yet.