Actually only one rat. But a really really smart one. At least we’d better hope that this one is smarter than average, or the human race is in grave danger.

Intercepting the first rat ashore, from Nature

In November 2004, we captured an adult male Norway rat by using a chocolate-baited trap … on the uninhabited and forested Pakihi Island… The rat was fitted with a radio collar and a DNA sample taken from its tail before it was released on a beach on Motuhoropapa… Our aim was to study the behaviour of this solitary invading rat and to test its susceptibility to standard methods of detection (independently of radio-tagging) and elimination.

All attempts from weeks 4 to 8 to capture or detect the rat using conventional techniques failed… After 10 weeks, the radio signal was lost. Fresh signs of the rat subsequently appeared… on Otata, which lies 400 m across open water. …the rat was not caught until 18 weeks after its release, when it was finally killed in a trap that had been baited with fresh penguin.

Our findings confirm that eliminating a single invading rat is disproportionately difficult.

No kidding. Clearly this rat is the protrusion into our dimension of a vast hyperintelligent pan-dimensional being. Yes, I know those are mice. But do you have a better explanation for how a rat outsmarted a team of humans with PhDs for 3½ months?