Bile acids can be divided into two groups: water soluble and non-soluble. Since long stagnation of the gallbladder can cause Gallstones to form, animals that can manage without food for long periods do not have gallbladders, e.g., camels. Some mammals, such as bears, that hibernate do have gallbladders, but they only produce water soluble bile acids. Therefore, the gallbladder's function is concerned with the control of non-water soluble bile acids. These are toxic and harmful to the liver and intestines if they continually circulate and reabsorb. The gallbladder's function is to store them, protect the liver and intestines from the toxic bile, and release them safely only when required.