The 57 mutts rounded up at the Cerro de la Estrella park, where the attacks occurred, include a few about the size of a Labrador, but many are small or mid-size dogs, including beagle and border-collie mixes. Twenty-three are puppies or very young dogs.
Many look like the discarded pets they are. Residents near the 353-acre (143-hectare) park in the poor Iztapalapa neighborhood say people regularly drop off unwanted pets there, but say the dogs have never caused problems before.
Moises Heiblum, professor of animal behavior at the school of veterinary medicine at the National Autonomous University of Mexico, said feral dogs as individuals "probably could not carry out a ferocious attack of this type" and normally avoid human contact.
But the dynamics change when a pack is formed, Heiblum said. "When a group comes together, they are capable of an extremely intense and even fatal attack. That is possible."
Animal control warden Armando Garcia, who was patrolling with an assault rifle this week, said there was no question that strays had formed a pack in at least one part of the park.
"You can tell when there's a pack: There's an alpha dogs and his followers, and they've marked out territory and they challenge you when you enter it, with growls and barking," Garcia said.
On Friday, authorities in Iztapalapa announced that the dogs taken into custody would be put up for adoption. They had earlier promised animal rights groups that the dogs would not be killed.
The dogs will get shots, special baths and medical treatment before being given away.