In 1931 Australia, the Australian government re-located mixed-blood Aborigine children far away from their mothers as a way of integrating them into white Australian culture because Aborginal culture which was considered unsuitable for children who were part white. This movie is based on a book written about the true story of three girls who were re-located far from Jiglaong, their ancestral home, then walked all the way back there. They navigated by following the Rabbit-Proof Fence, a pest-exclusion fence more than a thousand miles long that was built to try to keep alien rabbits and other pests from Eastern Australia out of Western Australia pastoral areas.
At the start of the movie we see a family of Aborigines tracking a monitor lizard (a goanna.) One of them, Molly, a 14-year old girl, finds the goanna in a tree and pulls it down by its tail. We don't see anybody kill it, but we do see her carrying it dead on her back to a woman who will probably cook it for dinner. Molly is one of the three girls who hike the fence to get back to Jigalong.
I'm not sure what species of Monitor it is, but it might be a Spencer's Monitor, Varanus spenceri.