An East Palo Alto resident was arrested for animal cruelty after police found a dead rooster and 56 birds, some injured, at a home where there was a cockfighting operation, according to police.

Reports of a potential cockfighting operation and a neighbor’s aggressive dog loose in the neighborhood led East Palo Alto police and a Peninsula Humane Society investigator to the home in the 1200 block of Cypress Street about 3:50 p.m. on March 23.

Officers found a dog in the backyard of the residence trying to attack some roosters and hens, East Palo Alto police said, but the dog was not aggressive toward the officers and the birds’ injuries did not appear to have stemmed from the dog.

Police found numerous cages along the back fence of the yard. A dead rooster was on top of one of the cages and two or three of the birds appeared injured, police said.

Christina Hanley, a lead humane investigator with the Peninsula Humane Society and Society for the Prevention of Cruelty to Animals who responded to the scene, confirmed that the birds’ injuries were consistent with birds used in cockfighting.

“When we arrived on scene, it was clear dozens of roosters had been modified and trained for fighting,” Hanley said. “Most of the roosters had been ‘dubbed’, a very painful process in which their comb, wattles and earlobes are cut off. This type of modification of roosters is consistent with cockfighting.”

Many of the birds still had open and bleeding wounds, possibly three to four weeks old, from the dubbing process, according to the Humane Society.

Investigators also found in an open shed on the property tools associated with cockfighting such as knives that are attached to the rooster’s legs and antibiotics used as treatment for the birds.

Buffy Martin Tarbox, a Humane Society spokesperson, said all of the surrendered birds have been euthanized as humanely as possible.

“Unfortunately, a good majority of those birds suffered horrific injuries either from the dubbing process or from actual fighting and we just felt it was the most humane thing to do to end their suffering,” she said. “Cockfighting birds are bred to be incredibly aggressive so it’s difficult for us to adopt them out.”

The suspect, Aldenni de Jesus Trujillo Santiago, 29, faces charges of animal cruelty and abuse, and being in possession of cockfighting paraphernalia and possession of cockfighting birds.

Officers issued warnings to correct all code violations, including removing the bird cages and two inoperable vehicles. The city’s code enforcement team also found two illegal out-buildings, illegal wiring and a potential illegal addition to the home.

The investigation into Trujillo Santiago is ongoing. To report information about this case or animal abuse, call the Peninsula Humane Society’s hotline at 650-340-7022, Ext. 601.