Rene Lozano is standing in front of a noisy Doberman explaining why single-handedly capturing a pack of nine dogs is not such a big deal. “Nine times out of ten the pack is gonna be chasing a female in heat,” he says. “I don’t care if it’s a pack of stray dogs, or owned dogs. All the male dogs are looking for the female.” Lozano gestures at the Doberman. “All I need to do is find the female. I mean, the female in heat will come to you. And then…” He throws his hands up. “There’s your pack.”

The lead pole is not, however, the tool that Lozano used to catch nine dogs on that day ten years ago. The lead pole, Lozano says, is not the tool for a pack. “You’ve got multiple dogs, dogs all over the place,” he explains. “I might be old school, but I use the wire.”

Tim Allen, a 19-year animal control veteran, has spent much of his career in the field as Lozano’s partner. The two men have worked on so many catches together that they have standard operating procedures for what would seem to be bizarrely uncommon situations: “Dog gets stuck in sewer,” Allen says, “that’s me. I’ve got longer arms.” Allen says Lozano’s a master planner. Before approaching a pack, Lozano checks escape routes, closes gates, figures out where dogs might go, finds out who the alpha is, what dogs are most aggressive, whether there’s potential for a rush. “He’s always got a plan A, and, if that doesn’t work, he’ll make a plan B on the fly,” says Allen. “There’s no one better to back you up.”

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On a cold Sunday morning in February, we’re heading north on South Loomis in a white GMC van with a net, two homemade lead poles, and the wire. A pack of eight to ten dogs has been spotted somewhere in or around Sherman Park, across from Arthur A. Libby elementary school. The 60-acre park, designed by Frederick Law Olmsted and distinguished by its classical field house and large O-shaped lagoon, is now one of the most pack-prone parks in the city. Nearby Englewood, with its many vacant lots and abandoned buildings, is also a notorious pack haven. Details about the dogs are scant and possibly exaggerated–they almost always are. People know, Lozano says, that if they use the words “vicious” and “kids” or exaggerate the number of dogs, they’ll get a response.

Fifteen minutes after we enter the park, Lozano spots the pack in an alley near the school. Clustered in front of two garbage cans are eight dogs, all of them brownish or black mutts, mainly terrier and shepherd mixes. From 20 yards Lozano zooms in on his target: the bitch in heat. “There she is,” he yells. “There she is. The brown-and-tan one.” We get back in the van and speed up the alley. The pack enters a fenced-in backyard. “This could be easy,” Lozano says excitedly, jumping out of the van, wire in hand.

Lozano works for one of the largest animal control operations in the world, in a city that has more dogs than Cleveland has people. In Chicago’s 230 square miles there are more than 500,000 dog owners and a probable dog population of nearly a million.

But disease control isn’t the city’s most immediate concern. Away from the structure of domesticated life, dogs revert remarkably quickly to canid instinct–they form packs. A pack of stray mutts in Englewood functions a lot like a pack of wolves in Yellowstone. Like a wolf pack, a dog pack is a rigid social organization. An alpha male leads; submissive males, who constantly fight each other to establish the pecking order, follow. Usually there is also at least one bitch in the pack. What alarms ACOs, though, is that pack dogs are more aggressive and dangerous than individual dogs. Scientists describe their increased aggressiveness as typical of mammal social behavior. Studies of dogs yield the same results as human crowd-theory studies: a teenager alone may be harmless; as part of a group he’s a punk. A submissive mutt in a pack will instinctually follow the lead of, and mimic the behavior of, a more aggressive dominant dog. If the alpha dog is vicious, the others will be vicious too.