June 9, 2005

Humans a Minority in Wild City by the Bay

By Daniel Porras
Special to the Neighborhood Newswire

From fungi to insects to rats, birds and coyotes, Josiah Clark knows about life in the city. San Francisco is not just a concrete human habitat, he says, but a thriving urban ecosystem “with a highly-stratified food chain.” As the ecologist who wrote the wildlife management plan for San Francisco’s small urban parks, Clark is well-attuned to our city’s wild web of life. And when it comes to the creatures of San Francisco, he’ll tell you, humans are definitely a minority.
At just under 800,000 people, San Francisco is the second most densely-populated city in the U.S, after New York. But how many other creatures share our seven-by-seven mile urban peninsula?

“There’s likely more insects in one acre of land in the Presidio than there are humans in the entire city,” says Clark, who talks about bugs mainly as a food source for birds - his favorite animals. Clark gives bird tours of the city and says that he once logged 122 different bird species on one bicycle tour of San Francisco County. On a busy spring day “there’s at least as many birds as people in the city, probably more.”

No one has done an animal census of San Francisco, so no one knows for sure how many critters share our space. However, using statistics compiled by the American Veterinary Medical Association, SF Animal Care and Control director Carl Friedman estimates that San Francisco is home to around 120,394 dogs. “And they all live in my neighborhood in Portrero Hill”, he quips. As for felines, which Friedman says are “more of a companion of choice” in San Francisco, the ACC estimates that there are roughly three cats for every dog. Give or take several thousand, that adds up to 480,000 cats and dogs in the city which, collectively, must house an impressive number of fleas. And each flea, as Jonathan Swift famously noted, “hath smaller fleas that on him prey; and these have smaller still to bite 'em; and so proceed ad infinitum.”

Offering “conflict resolution services for people and the wild animals sharing their space”, Urban Wildlife Management owner Alan Merrifield has worked closely with San Francisco’s wild creatures for more than thirty years. He gets calls from people with skunks and snakes in their kitchens, for example, or visits homes with sagging ceilings saturated with raccoon urine. According to Merrifield, the party gets started when the sun goes down. “While we’re sleeping, they are out there doing their thing,” he says of San Francisco’s non-human denizens: bats, gophers, moles, ground squirrels, crows, starlings, seagulls, pigeons, feral cats, garter snakes, mice; even an alligator in Golden Gate Park. And don’t forget the rats. “Oh we got rats,” Merrifield laughs, “about one per person”.

But the city’s animals aren’t all pests. Margaret Boeger of the California Academy of Sciences rattles off a list of native species found in San Francisco: Red-eared slider turtles, the endangered Western garter snake, rare chorus frogs, foxes, coyotes, deer, California quail, blue belly lizards, salamanders and newts. These mostly indigenous species are what ecologist Josiah Clark calls specialist species. They’ve evolved alongside native plants and insects, and are extremely sensitive to changes in their natural environments. City parks, gardens and yards create a patch-work habitat for these natives.

On the other hand, pests and rodents like ravens and rats, says Clark, are generalists, which means they adapt quickly to different environments and can utilize any resource. When humans pave over habitat, it’s the generalists that thrive. These animals “are very resourceful, and very athletic, and have no problem at all getting into most people’s homes,” says Alan Merrifield.

With populations of non-native, generalist species booming around the Bay Area, “it is in our best interest to keep native wildlife in the city,” says Josiah Clark. Coyotes, for example, keep rodent populations in check. Bats eat not only deer mice, which can carry deadly Hanta virus, but mosquitoes, which transmit West Nile virus. City dwellers, ironically, often reintroduce specialist species to control outbreaks of animals whose predators have been displaced by the city. SF Parks officials brought native owls to Golden Gate Park, for example, to deal with a booming gopher population.

“But the gopher isn’t bad,” says Clark, “they’re like little ecosystem engineers, turning over the soil, taking nutrients from underneath to the surface. Then the worms appear after the soil is turned over, and the robins come to eat the worms on top of the gopher piles. So it really is all connected.”