Zogre bones are associated with the Prayer skill. They are dropped by Zogres and Skogres. Zogre bones give 22.5 prayer experience when buried. There's a chance that a Skogre will spawn next to the player when these bones are buried inside Jiggig.
Zogre bones are generally less favoured by players training Prayer as they give less experience than their "relative" bones such as Fayrg, Raurg and Ourg bones.
These bones are often used on a Gilded altar for experience due to the tedious work required to worship the Ectofuntus.
Burying Zogre bones in Jiggig has a chance (approximately 1 in 4) to spawn a Skogre. If this happens, the buried bones will not give any Prayer experience, but the spawned Skogre will drop another set of Zogre bones when killed (as well as an Ogre coffin key). Skogres spawned this way have a short lifespan, and can de-spawn mid-combat.