"today in the bay's" stephanie truong has the connection to another neighborhood. >> you can see 20 to0 running around here. >> reporter: miles marken spends days and nights here at washington square park playing his guitar. he says there have always been rats in the city but in the last year it seems the rodent population has multiplied. >> i see them usually they come out at night but you can see them running across the field and everywhere around here. >> reporter: used to be one or two and now you are seeing packs of them? >> yeah. definitely increasing. >> doubling and doubling and doubling. >> reporter: the question is why and why now? the sf municipal transportation agency said rodents usually more active at the start of construction and the complaints began to build as the construction was winding down. they say it is possible something other than construction caused the ratted to come out. people we spoke to say they can't think of anything else. >> maybe disturbing the underground? >> lots of vibration in ground causes them to come up. >> reporter: and even the construction c