The look on Tessa’s face was one of nervous hesitation as she watched Nicole Campos climb the steps of the second floor South Side apartment.

“She was timid at first — she wasn’t sure what we were there to do,” said Campos.

The young Pit Bull Terrier’s bones were showing plainly against her fur, and Tessa’s neck was red with irritation from rubbing against the short, rusty chain that held her to the porch.

Sitting next to Tessa was a crate that Campos described as being “caked with about four inches of [excrement].” The dog’s feet were stained brown with urine, and an empty water bowl sitting next to her looked as if it hadn’t been filled in some time.

Campos and her team had arrived at the house on that early May morning on a tip from a nearby resident who said that Tessa had been left outside without food or water for a few days and appeared to be bleeding. The dog’s tail had been cut open from wagging against the sides of the small space to which she had been confined—a condition referred to, ironically, as “happy tail.” Both the dog and the porch were spattered with blood when the investigators found her.

“I walked right up and put the leash on her,” said Campos. “She was ready to go.”

The owners of the dog told Campos that they had recently taken in Tessa as a stray, but the neighbor had said otherwise. The investigators told the couple that they could either give up the dog or face intervention by the police. As is often the case, the negligent owners chose the former route.

A few minutes later, Tessa was in the truck and heading to the shelter.

Moments like these are the payoff cases for Campos and the rest of the Anti-Cruelty Society’s humane investigators program.

The six-person team responds to reports of cruelty and animal abuse within Chicago and the surrounding metropolitan area. The call center is located at the ACS’s main headquarters at 157 W. Grand Ave., where the organization has operated since its inception in 1899.

In addition to its humane investigators program, the organization runs an adoption program that has found homes for over 40,000 animals since 1999.

Most of the calls fielded by the investigators involve some form of negligence — cases in which animals are left out in extreme temperatures such as locked cars and backyards lacking shelter on hot summer days, or instances in which animals are made to live in unsanitary conditions or without food and water.

As licensed practitioners, the investigators are authorized by the Illinois Department of Agriculture to remove animals from homes, automobiles and any other settings in which an animal’s life is in danger — though they have to clear the investigations with state officials first.

“We can break windows, we can do whatever it takes to get that animal to a safe place,” said Campos, who is a field services manager and an investigator for the program.

Cases in which a possible misdemeanor or felony are involved are promptly handed over to state and local law enforcement officials. The most serious of these calls are the ones that involve dog fighting.

“Where there is dog fighting there’s drugs, guns, violent crime,” she said. “It’s bigger than an animal welfare issue.”

Campos said that the investigators are able handle most cases by simple mediation and instruction on the requirements of animal care — that is, the presence of food, water and shelter.

“Our goal isn’t to come and remove people’s animal — we have enough animals here,” she said. “A lot of it is an education issue. They may not know.”

Most cases involve dogs, with a minority of the calls related to cats and other small domestic animals. One issue that the investigators often deal with is pet hoarding, or the practice of not knowing when to say no to another animal in the house.

“It’s the people that end up with four or five dogs or cats, maybe they’re not altered and then they have litters, and before they know it they have 30 animals in their home,” she said. “It’s not that they mean to do harm to their animals, it’s just that it gets away from them.”

Cherie Travis is the commissioner of Chicago Animal Care and Control, an agency that impounds approximately 24,000 animals a year and has an average daily population of between 300 to 500 animals at its 54,000 square foot facility near Bridgeport.

Travis said that programs like the Anti-Cruelty Society’s humane investigators are a benefit to the city’s efforts to reign in animal abuse issues.

“We have limited resources, so certainly they are able to make some early evaluations to see whether something needs to be looked into further or if there’s merit to it,” she said.

Campos said that on average, the program fields about twenty calls per day, with a total tally of anywhere from 7,000 to 8,000 calls annually.

Call volumes usually increase in the very warm and cold months, and this uncommonly hot summer has been no exception. According to Anti-Cruelty Society data, calls to the humane investigators increased more than 100 percent over a recent two-day heat wave, and those numbers continue to be above average with the current high temperatures.

The organization also assists in cases throughout the State and the Midwest; in March, the Anti-Cruelty Society took in 27 dogs from a chain of puppy mills in Missouri.

Now 11 months old, Tessa is currently finishing up her obedience courses in the Anti-Cruelty Society’s Bully Buddy program for recovering Pit Bulls. A keen fetcher, Tessa has been up for adoption since July.

Campos said that Tessa seems like a completely different dog from the one she met chained up on that porch four months ago.

“She’s probably twice the size, she’s clean — a very sweet dog, considering what she’s gone through,” she said.