Recent studies show San Francisco is one of America’s rattiest cities; it also has a rat population that’s exploding in numbers.
San Francisco is swimming in a sea of rats. Not unlike New York City, the only American metro denser with year-long residents than San Francisco, the city’s rat population rivals that of its human inhabitants.
How many rats does San Francisco have, exactly? It’s hard to say, but it’s safe to estimate at least in the hundreds of thousands, potentially somewhere over a million. (As of writing, New York City has about three million rats; this figure represents an increase of 50% since 2010). It’s why pest control company Orkin recently found San Francisco to be the fourth rattiest city in America. Similarly, Science Advances used publicly available rat sighting data to follow population changes in the species for sixteen major cities, twelve of them being cities in the United States; San Francisco came in second in regards to rat population trend bending up, falling just behind Washington D.C. and even surpassing New York City’s observed rat growth.
Dr. Niamh Quinn, a human-wildlife interaction advisor with the University of California Cooperative Extension, said it best in an interview with SFGATE: “I keep telling everybody […] we live in an infinity of rats. There are rats absolutely everywhere.”
And the reason they’re everywhere isn’t necessarily a marketer who thinks things are getting dirtier and more decapitated. To the contrary, rats are synonymous with filth, but rather an abundance of resources. They can make food out of almost anything, from dog food to citrus grinds, and are resilient and adaptable, surviving in a wide swath of habitats; multiple generations can, for example, live inside drywall.
San Francisco has a trash problem. It also exists in a constant state of construction. Connecting the two with the city’s rising rat population isn’t exactly a brain teaser. But how to deal with this “infinity of rats” does come with conundrums.
You can’t simply poison them ad nauseam; native fauna, as well as cats and dogs, will inevitably prey on them and become poisoned themselves, not to mention their decaying positioned bodies leaking harmful chemicals into ecosystems and even our drinking water. Introducing certain genetic mutations into wild populations that sterilize mature adults is possible, but requires generations and years to produce tangible results. It’s also costly, and not guaranteed. Rat birth control is a thing — but it sits in the same canon of efficacy as gene manipulation.
Trapping works, though requires overhead and upkeep and opens doors to unethical practices. Fumigatory practices can kill hundreds, thousands even, with more control, but, like with poisoning, those dangerous chemicals can and will find their way into nearby ecosystems.
What remains the safest, most infallible means of rat reduction is reducing their resource, e.g. cleaning up street litter, increasing the frequency of trash pickups, and supporting local fauna that prey on them. And it’s the latter practice where San Francisco finds its polarizing allies: coyotes
Coyotes love vermin, particularly rats and mice. In urban areas, like San Francisco, rats and mice can make up as much as 75% of their diet. A single coyote can eat as many as 1,000 rats a year. Estimates remain gauzy on how many coyotes call San Francisco home, but UC Berkeley researchers put the number somewhere around 100 individuals. Simple napkin math means SF’s current coyote population could, in theory, be consuming 100,000 rats in SF’s city limits on an annual basis.
San Francisco’s coyote population is also stable. In fact, these medium-sized canids are incapable of overpopulating— a phenomenon observed in other like-sized and larger ground predators, like bobcats, mountain lions, brown bears, and wolves — and play key roles in maintaining balanced ecosystems where they’re found. Coyotes are nature’s perfect pest control agents, quite frankly. And, thus, potentially San Francisco’s biggest ally in curbing its rat infestation problem.
Fellow San Franciscans, we can embrace our four-legged shadow overlords (read: our population of urban coyotes) or allow rats to invade our living spaces with growing frequency. The decision is ours … and one option doesn’t harken back to the black plague.
Feature image: Courtesy of Presidio National Park
