The common myth that dogs wander off so that they can die alone is not entirely accurate. While dogs who are sick or in pain may feel vulnerable and seek out a safe, secure location, they do not leave for the purpose of finding a place to die.
Aging dogs sometimes develop a disease known as Canine Cognitive Dysfunction Syndrome (CCDS), which is similar to Alzheimer's disease in humans. Dogs with this disease many venture outside of their normal territory and become disoriented and unable to find their way back home. If unable to find water, food, or shelter lost dogs with dementia may die as a result.