They burrow in gardens and shelter in nests of shredded cardboard under stoops. In alleyways, they quench their thirst at leaky faucets and snack on liquids oozing from bags. Rats are a fixture of urban life, but early in the pandemic, their populations in urban cores shrank as restaurants, parks and offices shut down — and their access to trash did too. But many adapted, desperate to survive. They ate off the bottom of restaurant doors in search of food, alpha male rats ate weaker ones, and a large number, to residents' frustration, migrated. "They've gotten into places where there were no rats, and now people are calling and saying, 'I've lived here for 20 years and never seen a rat until now,' " said Gerard Brown, who oversees rodent control at D.C. Health. Now with offices and restaurants opening up again, the rats are back as well. "There's a rat resurgence," said Bobby Corrigan, among the world's best-known rodentologists. "Th...