Life expectancy of Cocker Spaniels
The time when a dog crosses the threshold from mid-life to seniorhood is highly individual. Your 9-year-old dog could be a senior, but the 9-year-old pooch who lives down the street may not be. The 5-year-old dog who used to gallop around your local dog park may now be a canine elder, while another 5-year-old pooch may be as active as a 5-year-old human child.
A good way to estimate when your dog will become a senior is to find out what his life expectancy is. The longer a dog is expected to live, the later the onset of seniorhood will occur.
A matter of breeding
Breed plays an important role in determining how long a dog is likely to live. Some breeds simply live longer than others. For example, the average Toy Poodle is likely to pass his 14th birthday before mortality catches up with him; by contrast, a Bernese Mountain Dog isn't likely to live much past the age of 7. Scientists aren't exactly sure why breeding affects longevity, but they have a few ideas.
Research indicates that inbreeding (breeding close relatives to each other) may be a factor that affects a breed's longevity. Some dog breeders advocate inbreeding as a way to boost the odds that a particular trait or characteristic is passed on to future generations. For example, when a breeder wants to ensure that puppies have ears that fold over rather than ears that point upward, he may breed two half-siblings who both have the ears he desires.
The trouble with inbreeding is that it may not only increase the likelihood that the puppies will have a positive characteristic, but it may also increase the odds that they'll have an undesirable characteristic. For instance, if the two half-siblings with pretty ears also both have a gene that makes them vulnerable to a certain kind of cancer, their puppies are almost guaranteed to have that same gene.
The pure-breed approach
Related to the inbreeding factor is the practice among some breeders of using the same male dog to father puppies from many different females. If the breeder uses the same male dog over and over again, other males aren't used and their genetic characteristics disappear. Meanwhile, the male dog who's getting all the action may be passing negative characteristics along with the positive to his progeny. If those negative characteristics affect life expectancy, eventually the breed's overall life expectancy decreases.