They weigh around 10 pounds, move mostly at night and don't leave any trace. They are friendly, fast and, perhaps most importantly, a critical part of California's ecosystem, as they help, not hurt, their surroundings and those who occupy it.
The gray fox features a "silvery-gray coat with conspicuous patches of yellow, brown, rust, or white on the throat and belly," according to the California Living Museum. They are "the most common fox in California, mainly populating coastal or mountain forests at lower elevations."
And right now, especially in the Central Valley, the nocturnal critters are increasingly visible. Those who work closest with the foxes said their numbers seem to be on the uptick this year..
"I didn't have a chance to see how many foxes we got this year, but probably close to 30, more than twice what we normally get," Donna Burt, the executive director of the Stanislaus Wildlife Care Center, told SFGATE on Tuesday.
The center is located in Hughson, about 9 miles southeast of downtown Modesto. The nonprofit's mission, she said, is to rescue and rehabilitate area wildlife brought in by members of the public.
The center serves an area that stretches from Merced to Stockton. This year, thus far, Burt said there has been a notable surge in the number of gray foxes coming through the center.
"We have two fox cages, and they were full and spilled over into a third," she said, explaining that the center, which relies on donations and volunteer help from local veterinarians and vet techs, was able to release all the foxes they rehabilitated.
"We get a few that are injured," she said. "Some we are able to save, some we are not -- but if they come in with us, they're in bad shape."
Wildlife biologist Burt, who founded the center in 1984, said she didn't really know what to attribute the spike in numbers of foxes to this season, other than the natural ebb and flow of wild animal populations.
Burt noted that the omnivorous foxes are an important part of the native plant and wildlife ecosystem here. "A lot of wildlife populations have boom and bust cycles. When prey animals have good years, the predators reproduce successfully. Then the prey animals decrease, and the predators decrease. They go up and down as a normal cycle."
The foxes are among the predators, but they are seen, by and large, as helpful in controlling the populations of their prey, mostly rodents. "They go after mice and gophers, baby birds," she said. "Foxes, they love their mice. They love mice. And they like dog food and cat food. They climb fences and wander around the city quietly and secretly. They're small and they're harmless. A 10-pound fox is a big one."
"I can tell you that the grey fox is pretty much in all of the Central Valley cities from Fresno north," Krysten Kellum, a spokesperson for the California Department of Fish and Wildlife, wrote in an email to SFGATE on Wednesday. "Foxes are intelligent, curious, and highly intelligent. Do not feed a fox. They are at risk of food conditioning or habituation to people."
The gray foxes are cousins to the San Joaquin kit fox, a species added to the Endangered Species Act in 1971 and mostly found farther south near Bakersfield. They're also related to the red fox, which is also not endangered but is more commonly seen at elevations of 2,500 feet or higher. Both gray and red foxes have had more of a presence around Modesto this summer, wildlife officials said.
"These fox species may be seen in diverse habitats statewide," Kellum continued. "Foxes provide many ecosystem benefits helping control rodent and other small prey populations, such as squirrels and rabbits."
Michael Hart, a volunteer with the California Department of Fish and Wildlife, often visits the Tuolumne River Regional Park on the riverfront, which is about 3 miles from downtown Modesto and next to the regional airport. He told the Modesto Bee recently that he's seen more of the foxes while he's out on patrol.
"You'd look out here and you'd see three, which is kind of unusual," Hart told the Bee.
As far as numbers of actual foxes that are out and about in the valley this summer, Kellum said she wasn't sure if the gray fox population is actively being tracked: "CDFW monitors/manages CESA-listed species or game species but not necessarily all species," she wrote.
Burt of the Stanislaus Wildlife Care Center said it is tempting for humans to interact with the gray foxes, given their cuteness and friendly dispositions. "They have kind of a little skittish but sort of mellow personalities," Burt said. "They don't attack things. They run away and hide."
However, both Burt and Kellum cautioned against interacting with and feeding the foxes. "It's important to keep wildlife wild," Kellum said via phone.