More than 1.5 lakh stray dogs roam the streets of Calcutta, mayor Firhad Hakim said on Thursday amid a polarising debate over how to protect these animals while ensuring their burgeoning population does not affect citizens.

Hakim, also the minister for urban development and municipal affairs, cited the figure while speaking about plans to start a sterilisation drive to keep the population of stray dogs on a leash.

A civic official estimated that there could be one stray dog for every 30 people in a city as thickly populated as this. The 2011 census had put Calcutta’s population at 44 lakh-plus.

Based on Hakim’s ballpark number, each ward of the Calcutta Municipal Corporation could have about 1,040 stray dogs. The city has only two pounds for stray dogs, one in Entally and the other in Dhapa. Between 15 and 25 dogs are sterilised there daily.

Hakim said the infrastructure was inadequate to limit the population of strays. An animal rights organisation that had conducted a survey of street dogs in Calcutta in 2007 found about 55,000 strays.

Dogs loitering in the wards of state-run hospitals and on college and university campuses is a common sight. Almost every neighbourhood has strays that chase pedestrians at night.