Scientists have long puzzled over whether dogs have a social hierarchy similar to wolves (Canis lupus), their closest relatives. Wolf packs are typically made up of a nuclear family that’s led by a single breeding pair. But dogs living with human families are often placed with other unrelated dogs, and many of them may have the potential to breed. To find out if there is a leader in such groups, researchers tracked the paths of six dogs cared for by one owner as they took a series of walks. Five of the dogs were Vizslas, a Hungarian hunting breed, and one was a mixed breed. All were outfitted with high-resolution GPS harnesses (as shown in the photo above) that mapped their paths as they all traveled away from their owner and back again through an open grassy field; the owner also wore a GPS unit on her shoulder. Dogs that consistently took the lead were older, more aggressive, and more trainable than dogs that followed , the scientists report online today in PLOS Computational Biology. The scientists also determined that the leaders in this group of dogs were the most dominant. Dog leaders were followed in nearly 75% of their interactions with another dog—which is similar to the amount of time wolf pack leaders direct their followers. There is one key difference, though, between the wolf and dog leaders: While leadership in wolves is tied to an individual’s reproductive role, it apparently is not in dogs, at least not in this group. The main leader among these six was a neutered female. Thus, even without a breeding pair to direct them, the dogs in this group organized themselves into a hierarchy, and paid attention to the leader of the pack.