Now the details I have are vague, but I remember that there was a human boy who was accompanied by an adult-sized alien, who I think was hairy and maybe had a sort of anteater-looking face. The scene I remember the most is when these two characters are walking through a swamp, and the alien gets caught by living vines and is killed.
This could be either an American film or an anime that was dubbed, but I have no idea.
The Masters of Time (original title: Les maîtres du temps) has a scene which fits this description.
From Wikipedia:
Les Maîtres du temps (lit. The Masters of Time, a.k.a. Time Masters, Herrscher der Zeit in German, Az idő urai in Hungarian) is a 1982 Franco-West German-Swiss-British-Hungarian animated science fiction feature film directed by René Laloux and designed by Mœbius. It is based on the 1958 science fiction novel L'Orphelin de Perdide (The Orphan of Perdide) by Stefan Wul.
The film centres on a boy, Piel, who is stranded on Perdide, a desert planet where giant killer hornets live. He awaits rescue by the space pilot Jaffar, the exiled prince Matton, his sister Belle and Jaffar's old friend Silbad who are trying to reach Perdide and save Piel before it is too late.
You can view the relevant scene around the 59:44 mark in the video below.
