Dogs Really Are Man's Best Friend -- Here's Why

From Hachiko to Hawkeye, the stories of a dog's heartbreaking loyalty to their owners are endless.
ASPCA science advisor Dr. Stephen Zawistowski tells us that dogs are fiercely loyal simply because they evolved as pack animals.
"When they've moved into our homes and into our lives, our families have become their pack," says Zawistowski.
Watch to find out more about a dog's undying loyalty.
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