Like most monkey bones, they can be used to make a Greegree by taking it to Zooknock in the Ape Atoll Dungeon. Using these bones will create a monkey greegree (big zombie). Besides the type of resulting greegree and inventory icon, they are functionally the same as Monkey bones (small zombie), which are used to create small zombie monkey greegrees. Oddly, despite being the same size as other monkey bones, they have a smaller inventory icon.