Older dogs lose their homes for some of the same reasons befalling younger canines -- such as the owner's job loss or move to a residence that doesn't permit pets. Senior dogs often end up homeless because of their person's death or need for nursing home care. There are organizations that will provide lifelong care for senior dogs, but such sanctuaries are often full, with waiting lists.
Dog sanctuaries exist throughout the United States and Canada, ranging from small, family run shelters caring for a few dogs -- often with special needs -- to large operations such as Utah's Best Friends Animal Society, home to hundreds of animals. Some organizations might specialize in particular breeds or sizes of dogs. Others acquire old dogs from kill shelters rather than taking in pets directly from owners or temporary guardians. Many require a donation to take in an animal.
Many of the organizations providing care for senior dogs don't keep the animals in one specific location. Instead, they rely on foster care providers to care for these dogs. Some sanctuaries can place dogs in temporary foster homes until a space opens up at the primary care facility, while in other organizations, the foster home is the equivalent of a permanent home for an elderly canine.
Senior dogs don't necessarily need to spend the rest of their lives in sanctuaries. If a senior dog is relatively healthy, there's no reason he can't be adopted into a new loving home. Many pet rescues adopt out senior canines, conducting the same sort of screening of potential adopters as is done for younger pets. Senior dogs have certain advantages -- they're usually housebroken and don't require the same amount of exercise as younger, more rambunctious dogs. Older people or those with other elderly animals might desire a senior companion.
You must sometimes make hard choices with an older dog. Consult with your veterinarian if your senior dog requires a great deal of care or has serious medical issues. Your vet can assess the dog's health and temperament and help you make the right decision about what's best for his future.