Elderly Dogs. Like unhealthy dogs, elderly dogs, too, sometimes are surrendered to a shelter when their owners decide they either can't or don't want to take care of them anymore. Elderly dogs in shelters range from well-trained, extremely social animals to unhealthy, shy or reclusive dogs. Many people avoid adopting elderly dogs from shelters with the knowledge that their lifespans are much shorter than puppies, an adolescent or even an active adult dog. However, a calm, low-activity, elderly dog may be a great companion for someone who is relatively inactive. When adopting an elderly dog, the same guidelines apply as adopting an unhealthy dog. Elderly dogs may make great pets but they may also have medical problems that require expensive veterinary care. Elderly dogs have shorter life spans. People who adopt one should be prepared for the fact that these dogs are going to be part of the family for a shorter period of time than if they adopted a younger animal. If you're considering adopting an elderly dog, be certain you are comfortable with the increased risks of near-term health challenges and associated issues before you make a final decision to do so. Puppies from Unplanned Litters. Along with dogs that families can't handle, puppies from unplanned litters can be some of the most common dogs found in shelters. Animal shelters may get a pregnant dog and work to find homes for both mother and puppies or may get a litter of puppies from a family that found themselves with an unplanned litter. Spaying and neutering education has significantly reduced the number of puppies from unplanned litters, resulting in an overall decrease in dogs arriving in animal shelters. In the 1970's, as many as 15 million dogs passed through animal shelters every year, while today, 6 to 8 million dogs are processed through shelters and humane societies annually. Because unplanned litters are still relatively common, humane societies and animal shelters get puppies on a regular basis; on any given day, you can typically walk into a shelter and find one or more litters. Most shelters charge more for puppies than adult dogs, because puppies are much more popular to adopt. Still, shelter puppies are much cheaper than puppies from professional breeders and likely to be healthier as dogs from pet stores that are bred by commercial breeders or puppy mills. One significant benefit of adopting a puppy from an animal shelter is you may be able to get the puppy young enough to play a large role in its upbringing. With an adult dog, your task is to live with its personality and quirks. With a puppy, you can ensure it is socialized properly and bond with it early, leading to a lifelong companion. The disadvantage of adopting a puppy from animal shelters is that most puppies in shelters are of unknown breeds. You may adopt a cute little puppy that turns out to be a 100-pound dog in a year or two. If you're not prepared for this level of uncertainty, adopting a puppy from an animal shelter might not be the best choice for you.