As many as 1,000 stray-cat colonies have been reported in the city and county of Sacramento, California, with an average of 12 cats each. According to Front Street Animal Shelter manager Gina Knapp, however, a cat colony can contain anywhere from 7 to 100 cats, she told Capital Public Radio.
Dozens of feral cats hang out around Discovery Park. They are usually nocturnal and rarely visible during daytime hours, but experts say they pose a serious threat to humans and wildlife.
Feral cat colonies develop by a process called Trap-Neuter-Release/Relocate (TNR), which involves luring the cat into a trap and having it sterilized before releasing it either in the region it was found, but ften into a strange area.
The colonies are maintained by volunteers who leave large amounts of dry food, along with canned food, in open public areas. This easy food source lures honking geese, swooping magpies, multicolored cats and skunks in the California state capital city. Sacramento County officials say the cats here are a problem.
FERAL CATS CALLED ‘INVASIVE SPECIES’
“I would call them an invasive species,” says Sacramento County Park Ranger, John Havicon, who has worked in the park for 30 years. He says the cats have been there as long as he has and they go after song birds and native birds near the ground.
“The hawks, the owls, fox, raccoons are all dependent on the same food sources…the cat is taking those food sources, and so the [wildlife] will tend to go away," says Havacon. "So we will see less of the wildlife and more cats, or here, more skunks.”
Another serious health threat, Havicon says, is that the cats may not have had veterinary care, and they can pass diseases on to raccoons, fox, and other wild mammals which come into contact with humans or pets. The cats stay where people feed them.
Havicon says you can get a citation for feeding ducks and geese, but not for feeding the cats.
“It’s in [the cat feeders'] heart[s], they just have to take care of these animals," he says.
Dr. Karen Shapiro with the UC Davis School of Veterinary Medicine, also speaks of the compelling drive for some humans to maintain cat colonies and feed feral cats:
"[It’s] a natural human emotion and reaction, but unfortunately we don’t often think about the broad ecological impact that that can have."
OUTDOOR CATS CARRY DANGEROUS PARASITES
Shapiro says, in addition to devastating bird and rodent populations, the feces of outdoor cats carry dangerous parasites, like toxoplasma. When a cat is infected for the first time, it can shed hundreds of millions of parasite eggs, which persist in the environment for years.
"Toxoplasma is incredibly prevalent in people. It’s thought to infect about one-third of humans globally," Dr. Shapiro told Capital Public Radio.
The parasite can be fatal to people with compromised immune systems, and toxoplasma has also been linked to schizophrenia and behavior change.
But, Dr. Shapiro says, it doesn’t only affect humans.
“So in California, Toxoplasma makes its way into the ocean through freshwater run-off where it infects a large proportion of sea otters. Sea otters are classified as threatened and infectious diseases are an important cause of death in these animals."
Contaminated cat poop can wind up in our gardens, our storm drains, and eventually, in our drinking water.
Shapiro says the cat population can be managed through neutering and relocation to barns, but cats will still kill other critters and shed pathogens.
"There is no easy solution. I think as much as possible, we should aim to reduce and eventually eliminate such cat colonies," Shapiro says.