Wikipedia says that there are 32 million rats in New York City. Do you really think that many rodents can get their shit together collectively in just 2 days? I suppose it's about how they are "sensing" danger? One of them sees a vampire eating rats, so it runs, other rats sees a running rat and runs, and so forth until there's a stampede of 32 million rats heading towards Jersy. Or can they feel the Vampires telepathic wavelength?