Rats also inhabit subways, as most people in New York City and any city with a subway system are well aware. 'Often,' Robert Corrigan writes, ' 'city rats' will live unbeknownst to people right beneath their feet.' Rats can also nest in basements, sewers, manholes, abandoned pipes of any kind, floorboards, or any hole or depression. Sometimes there are networks of burrows, which can stretch beneath a few concrete squares on a sidewalk, or a number of backyards, or even an entire city block-when Rattus norvegirus first came to Selkirk, England, in 1776, there were so many burrows that people feared the town might sink. A bolthole is typically covered lightly with dirt or trash-camouflage. This second hole is called a bolthole it is an emergency exit. The back of the den then narrows into a long tunnel that opens up on another hole back on the street. The den is lined with soft debris, often shredded plastic garbage or shopping bags, but sometimes even grasses or plants some rat nests have been found stuffed with the gnawed shavings of the wood-based, spring-loaded snap traps that are used in attempts to kill them. This tunnel then travels about a foot down to where it widens into a nest or den. Entrance to a typical under-the-sidewalk rat's nest is gained through a two-inch-wide hole-their skeletons collapse and they can squeeze into a hole as small as three quarters of an inch wide, the average width of their skull.

'Alley rats can forage safely within the shadows created by the alleyway, as well as quickly retreat to the safety of cover in these narrow channels.' Often, rats burrow under concrete sidewalk slabs. 'Cluttered and unkempt alleyways in cities provide ideal rat habitat, especially those alleyways associated with food-serving establishments,' writes Robert Corrigan in Rodent Control, a pest control manual. Rat nests can be in the floorboards of apartments, in the waste-stuffed corners of subway stations, in sewers, or beneath old furniture in basements. They dig holes to enter buildings and to make nests. Anywhere there is dirt in a city, brown rats are likely to be digging-in parks, in flowerbeds, in little dirt-poor backyards. When it is not gnawing or feeding on trash, the brown rat digs.

Rats by robert sullivan