When New Yorkers see something scurrying, they say something and that has brought rat complaints to the city's 311 hotline to a high of over 24,000 so far this year, officials said on Thursday (22 October).

"The rats are taking over," New York City Comptroller Scott Stringer said. "I'm a lifelong New Yorker and I've never seen it this bad... I see them on my way home, they're standing upright, they say, 'Good morning, Mr. Comptroller'."

With more than two months of grumbling still left in 2015, rodent-related grievances were already at 24,375 as of 21 October, according to the New York City mayor's office. That's up from 20,545 in 2014 and 19,321 in 2013.

And that's just above-ground rats. Complaints about vermin in the subway are routed to the Metropolitan Transportation Authority and not recorded by the 311 line. The New York City Department of Health and Mental Hygiene laid the blame, in part, on a new 311 mobile phone app in use since February 2014, making it easier to rat out the pests to the city's hotline that has been operating since 2003.

"As if no one knew this before the app - it's just not true," Stringer said. "It's a lack of taking care of business by the city's health department."

The city is spending $2.9m (£1.9m) to expand a pilot programme to eradicate "rat reservoirs," attacking them in the colonies they set up in parks, subways and sewers, according to the health department. Exterminators set out bait, close burrows and work with the neighbouring community on best practices to avoid attracting them in the future. New York City residents agreed that more must be done to combat the rat issue.

"I think a lot of it has to do with the sanitation department," Marvin Lasky said. "They don't pick up the garbage and they leave the streets ripe for rats to be around."

"They put some traps but I don't know if they're working on it or if they check the traps very often, also poison," Maria Guzman said. "I think they need to put more attention on this because it's a lot."

"This is something that they're going to have to tackle and it's going to have to be an aggressive tackle with the pest control for them to get this under control," Roger Blondell said.

Last year, a Columbia University researcher estimated the population at about 2m, far fewer than traditional estimates of 8m, or one rat for every human in the most populous US city.