Hurricane Sandy's aftermath: Will rats take over Manhattan?

"The 8-million-strong human population of New York City is matched, if not exceeded, by the city's number of rodent dwellers," says Lynne Peeples at The Huffington Post. And lots more rats lost their homes — subway tunnels and sewers — to flooding from Hurricane Sandy than people did. What has become of those disease-carrying vermin?

"Rats are incredibly good swimmers," says Rick Ostfeld of the Cary Institute of Ecosystem Studies, ominously. "And they can climb." If Sandy did indeed flood them out and upset their social structure, "rats could start infesting areas they never did before," and the result could be a public health mess, with potential outbreaks of leptospirosis, typhus, salmonella, even the plague. In other words, "a rat disturbance is something we should be concerned about."

Well, so far at least, the "ratpocalypse that threatened to destroy humanity (at least in New York)" hasn't materialized, says Dan Amira at New York. There's been no notably increased above-ground presence of the rodents, and "in fact, the flood may end up as a net positive, as far as we people are concerned." Why? Flooding kills young rats, so the overall rat population may well decrease.

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Unfortunately, it's not that simple, says Adam Clark Estes at Vice. Many, if not most, rats will drown, but "those that make it out of the flooding will be treated to a veritable feast of garbage and debris that washed into the tunnels during the hurricane," and they'll be able to gorge and reproduce freely in the deserted subway stations. And if the flooding killed the submissive rats that scavenge for food in the daytime, leaving the dominant, nocturnal rats alive, "New York's rat population may have just gotten stronger."

This fixation on a great rat invasion makes sense after a calamity like Sandy, says Robert Sullivan at The New Republic. "We find rats terrifying, a measure of the breakdown of everything we think of when we think of civilization." But it's important to remember that "rats rarely live up to headline writers' fantasies." Let's start by debunking the myths: First, there aren't 8 million rats in New York; there are more like 250,000. Second, "hordes of Norway rats, North America's predominant rat species, do not live deep in the subway tunnels," they live where the food/garbage is — on the subway platform and in parks:

After September 11, rat populations increased in Lower Manhattan precisely because the area was cut off to people. Restaurants near the old World Trade Center that were abandoned were suddenly akin to rat farms... The Lower Manhattan rat population increased dramatically, and, as a result, the city Department of Health built a ring of poison-filled bait stations around the abandoned areas, eventually beating down the population explosion. This week's flooding just means... Keep your food secure and be vigilant.... And we know that after a flood event, the water itself — contaminated with raw sewage, as well as petroleum products and all the not-as-terrifying pollutants that normally cover our streets — is potentially more of an issue in terms of spreading pathogens than rats.