Dogs have earned the title “man’s best friend” for good reason. Consider a South Carolina dog named Killian, who is being hailed as a hero for outing an abusive babysitter. The normally friendly mixed-breed pooch became extremely agitated and even aggressive whenever the babysitter arrived at his family’s house. With their suspicions raised by Killian’s out-of-character behavior, his family hid a phone under a couch and recorded the babysitter cursing at and striking their 7-month-old son. Killian deserves more than a few scratches behind the ears for that!

Dogs’ loyalty to their guardians knows no bounds, but not every dog has a family to love. Animal shelters across the country are overflowing with mutts like Killian, who would make faithful companions if only someone would give them a chance.

Many people who have adopted dogs from shelters say that their dogs are extremely devoted and seem especially grateful to have a home. Some adopted dogs have even returned the favor by alerting their guardians to danger, summoning help or risking their own lives to save the humans who once saved them.

An adopted dog in Connecticut named Duke was credited with saving the life of his family’s 9-week-old daughter, who had stopped breathing during the night. Shaking uncontrollably, Duke leapt onto his guardians’ bed and awakened them. Duke’s guardians instantly knew that something was wrong and went to check on their baby. Paramedics were able to revive the girl, thanks to Duke’s quick action.

It doesn’t take long for adopted dogs to form protective bonds with their new families. Just hours after a couple took him home from a shelter in Ohio, a dog named Hercules chased off a burglar who had apparently cut the phone and cable lines and entered a basement door in the back of his new guardians’ home.

Some adopted dogs even act as guardian angels to their rescuers. Bear, a shaggy 100-pound dog, was once kept in the back of a Texas animal shelter because nobody wanted him. But eventually, a kind woman who happens to suffer from complex partial seizures adopted him. Without any known training, Bear now senses when his guardian is about to have a seizure, warns her by leaning on her legs and even fetches her medicine for her. One day, Bear’s guardian fell during a seizure and was knocked unconscious. Bear reportedly scratched on every door in the neighborhood, but no one answered. Finally, the smart dog spotted an animal-control officer and summoned her for help. “I rescued him. He rescued me,” said Bear’s grateful guardian.

Other dogs plucked from shelters have gone on to sniff out drugs, act as ears for hearing-impaired people and even become movie stars, such as Uggie – the canine star of “The Artist” – who was passed off by two families before he found a wonderful permanent home. And countless dogs have “rescued” their lucky adopters from depression and loneliness.

Shelters are full of amazing dogs, but there simply aren’t enough homes for all of them. Breeders, pet stores and people who don’t spay or neuter their animals worsen this crisis, because every new puppy means one home fewer for the dogs still waiting in shelters.

We can help change that by opting to adopt animals from shelters instead of buying them from breeders or pet stores and always having them sterilized. Whether you’re looking for a playful pup or an affectionate adult who is already housetrained, you’re sure to find the perfect dog in a shelter. Adoption fees are far lower than what pet stores and breeders charge, and they usually include the cost of spaying or neutering, microchipping, deworming and vaccinations.

Best of all, adopting saves a life. And who knows? It might even save yours one day.