What if 85 Million Wharf Rats Crashed Martha’s Vineyard?

Here at ‘Inverse’, we like to explore horrifying, if unlikely, scenarios, which is why we’ve publicly mulled what would happen if Cleveland’s dead rose, if a Tyrannosaur got loose in Minneapolis, and if there was a nuclear meltdown in Kansas. This week, we consider a rodent influx of unusual size to a sleepy New England isle.

Martha’s Vineyard may be a lovely island off the coast of Massachusetts, full of frolicking Kennedys and budget-blown vacationers, but it has visitors of a smaller, furrier variety. The wharf rat, Rattus norvegicus, scampers around the island (as well as the rest of the continental United States). But what if there were a whole lot more wharf rats — a surge in population proportional to the 87 percent annual exodus of humans during the fall months?

Just how many rats are we talking about? Rats are notoriously tough to count, though would be census-takers have tried; estimates of rats in New York City range from a scientifically plausible 2 million critters to the old you’re-never-more-than-six-feet-from-a-rat saw of 8 million. We’ll take the ungenerous assumption that peak Martha’s Vineyard wharf rat is a wharf rat per person, too, and, therefore, flood the island on a premise of 85 million rats (that’s about 53 million pounds of rats).

Rodents mesh nicely with Martha’s Vineyard ecosystem, shaping the vegetation by recycling seeds in their poop and in turn providing teeny four-legged meals for hawks and owls. But rats — voracious, fecund, almost superheroic in their adaptability — have a way of gumming up the system, and they’ve already begun to clog up Martha’s Vineyard before we dropped our rodent payload on the island. “We have a big problem,” the West Tisbury Executive Secretary Jennifer Rand told the Vineyard Gazette in 2004, speaking of the rats that had colonized the town hall.

A huge and sudden influx of foreign biomass has a tendency for catastrophe. Humans have used that to their advantage; in 2013, the U.S. airdropped a few thousand mice, pumped full of acetaminophen, on Guam to kill invasive snakes. When the rat population northeast India skyrockets once every five decades — thanks to the blooming patterns of bamboo — these rat armies eat so much vegetation wildlife dies and farmers become destitute to the point of apathy. There are no crops on Martha’s Vineyards — but outside of the summer vacation months, there are a lot of empty homes: 63 percent of the housing is seasonal, which rats infiltrate through cracks or by chewing through the rubber garage liner. Given that a rat can eat up to 30 grams of food a day, that’s 5.6 million pounds of Martha’s Vineyard going down the rat gullets.

Initially, the hawks and owls feast, until the rats turn to bird eggs as a source of food. Gray foxes and coyotes — if, as a handful of sightings indicates, they exist on the island — are the land vertebrates that fare the best. The pigeons have no chance. Humans have the choice of sticking around and fighting the rat flood — and facing down a variety of rodent-borne diseases to boot — or waiting it out on the mainland. Eventually, the island either reaches a new equilibrium of rats, or the Vineyarders take a page from rabbit-plagued Australia and release a virus meant to kill off the rats. This will work until disease-resistant rats breed themselves back.

We win the battle; we lose the war. A couple million years down the line, humans die off, and hyper-intelligent rats have as good a shot as any to take our place.