A rat snoops around a trash can at 15th Street and Vermont Avenue. (Michael S. Williamson/The Washington Post)

The complaints and questions started off slowly. Then came an avalanche of rat woes.

In less than an hour, in the early afternoon Thursday, the D.C. Departments of Public Works and Health had fielded online questions from more than a dozen District residents who were frustrated, tired and even perplexed. They wanted to know how to deal with rats in a city where — according to officials — rats number in the hundreds of thousands.

There was Erin, who thought rats had infiltrated her basement from next door. There was Matt, who could see rats running around his back yard. And there was Wesley, who claimed that the arrival of a Subway sandwich shop on the ground floor of his building had caused an “explosion of rats” that “constantly climb the stair case.”

Katy wanted to know how bad it was that her cat happened to be a masterful rat hunter, bringing dead rats home — “I counted a dozen last week — five in one night.” Steve was frustrated because he could hear rats but couldn’t see them. Then came Portia, who asked the question: “People are definitely grossed out by rats in their homes, but do they need to be?”

The short answer is yes.

And on Thursday, District officials ran through a number of reasons why — and what D.C residents can do about it.

The discussion marked the second such online chat about rat problems in the District, and was jointly hosted by the Rodent and Vector Control Division of the Department of Health and the Solid Waste Education and Enforcement Program at the Department of Public Works. If ever there was a perfect marriage.

The “renowned urban rodentologist” Robert Corrigan joined city officials for the discussion, offering such thoughts as, “Rats can be very cool animals,” along with serious advice about how to keep those cool animals as far away as possible.

According to Corrigan, “one rat is too many.” Rats have parasites. They can gnaw through wires — potentially causing fires — and can cause a whole lot of structural damage.

Rat problems should be dealt with “immediately,” and residents can dial 311 to report rat sightings or request Department of Health inspections.

The other big takeaway for those who have a rat problem: Find out what the rats are eating and eliminate it. Doing that probably eliminates the rat problem.

Of course, that’s a whole lot easier said than done. (As Public Works puts it: “The worldwide struggle against rodent infestation has been well documented over centuries.”)

Not only do rats like yesterday’s dinner and other items from the garbage, but they’re also into acorns, berries and dog poop, as it happens.

“Rats eat dog poop,” the department says. “When you do not properly contain these bags you are encouraging rodent infestation in your neighborhood.” Yum.

So what can Public Works do about your rat problem? In many cases, it turns out, not a whole lot.

The department says it will not solve rat problems in a private home, but it can inspect the “exterior” of the home. For indoor rats, like Erin’s, you’ll need to hire a private inspector.

To John, dealing with the problematic mulberry tree on a neighbor’s property, the department said: “The only thing we can suggest is to sweep up or hose down the public space as often as possible until the harvests stops.”

And when James complained that rats were eating his garden, the department admitted: “Unfortunately, there are very few things rats don’t eat so we have no suggestions of other things you can safely plant. Sorry!”

Wesley, who said he had contacted the Department of Public Works about the rat “explosion” downstairs and was told there’s nothing the department could do because the complaint involves a private alley, got this curt response:

“Hi Wesley, please put in a service request through 311 for this location and DPW will definitely come out and investigate. Thank you.”

District officials did take the time to discourage people from littering, dispel some rat myths and throw out some useful and weird rat facts.

For one, mice do not grow into rats. (For the record: No one in the online chat asked about that, and it was unclear who actually believes it. But in case that person is you, reader, here is an explanation from Public Works: “Mice are mice. Rats are rats. These are two different animals. Mice do not grow into rats.”)

Another one: Rats do not have collapsible skeletons. What?

And finally: Alka-Seltzer does not poison rats. Sorry.

What is true about rats?

The most common species of rat in the District — yes, there are several—is the Norway rat. The roof rat is another. And they rarely bite people.

Rats eat through spray foam, but not, apparently, steel wool or cement, so use one of those materials to patch up a potential rat entry point to your home.

Don’t take a rat to an art gallery or the theater — it won’t appreciate the view. Apparently, rats have such bad eyesight that they have trouble distinguishing between a person, a tree “or some other vertical object” — which usually explains instances in which rats get a little too close.

And rats do not fill out government census forms. (From Public Works: “The rats do not fill out a census form.”) So the estimate that humans outnumber rats by about three to one is just an estimate.

After an hour’s discussion, the time was up. Next up for Public Works’ online live chats: vacant lots and abandoned buildings! Tune in at noon June 25.