"One researcher... accused the dogs in the National Park of Brasilia, where they hunted in massive packs, of scaring off natural predators."

"It was found that the closer humans lived to a nature preserve, the more likely dogs had penetrated it But perhaps most striking? The dogs were neither feral nor domestic — but somewhere in between. 'All the dogs we detected had an "owner" or a person that the animal has a bond with... The species population increases following human populations, exacerbating their potential impact on wildlife.'... [Researchers] set up cameras and discovered dozens of dogs in the [Tijuca forest, one of the world’s largest urban woodlands]. They estimated more than 100 dogs were in the park — not residents, it turned out, so much as frequent visitors, tracking in from nearby favelas. 'These are people who are very poor... They don’t have money to build walls. . . . When the owners leave for work, the dog leaves, too, and only returns when the owner comes back to the house from work.' The owners often have no idea what their dogs are up to. Even if they were told... they almost certainly wouldn’t believe it.... 'We’d do interviews with the farmers: "Have you seen these dogs?" And they’d say, "Yeah, but my dogs aren’t the problem; it’s my neighbor’s dogs."'"

From "The dog is one of the world’s most destructive mammals. Brazil proves it" (WaPo).