Some 1,000 more rat burrows were detected last year in public areas compared with 2014, said the National Environment Agency.
The total number of rat burrows last year: 43,000.
Some experts say that each burrow could have as many as 30 rats. This is an indication of a worsening rat problem, say pest controllers.
If left unchecked, a pair of male and female rats can be responsible for producing more than 1,300 rats in a year.
In response to queries, NEA also said that about 85 per cent of burrows were found in housing estates managed by town councils.
Mr Hadi Hanafi, technical director of Innovative Pest Management, said his company has received a three-fold increase in rat-related calls in the last two years.
Mr Hadi, 34, called the increase in burrows “very significant”.
“This shows that we have to be more well versed in tackling rat issues and to be vigilant. We not only have to catch the rats, but also go to the source to stop the rats from reproducing,” he said.
He also revealed that his company has been getting an increasing number of calls about rat infestation in shopping malls.
“This is due to all the upgrading works that are happening. When one shopping mall gets upgraded, they will tear down the walls which ‘disrupts’ the rats. And the rats will move.”
He said that while sewer or Norway rats are usually found in drains or HDB blocks, roof rats are the ones infesting the malls, and chewing up the ceilings. (See report above.)
Similarly, Dr Chan Hiang Hao, medical entomologist with pest control company Rentokil, said 10 per cent of the calls the company receives each day are rat-related.
On average, Rentokil receives 60 rat-related enquiries via telephone monthly.
Dr Chan told The New Paper: “Rats are one of the top five pests (in) enquiries monthly over the past two years.”
According to Dr Chan, all it takes are food, shelter and water for rats to find a home.
“Burrows are commonly dug by the pregnant rats where there is food and water available.
“One cm is all a rodent needs to enter a building. Old buildings without consistent or regular maintenance are most at risk of allowing entry points for rodents, through cracks, gaps and crevices,” he said.
In 2011, the NEA started an island-wide surveillance programme to monitor the rodent population.
Apart from detecting active rat burrows, potential causes of infestation like potential food sources are identified through this effort.
To further tackle this rat problem, a more coordinated approach among multiple stakeholders – including town councils and food shop operators – was piloted in Redhill Close, Bedok Central, Clementi Avenue 3 and Bangkit Road..
These stakeholders play their part through efforts like engaging their own pest control operators and coordinating their own rat control plans.
NEA has said that early results show a 15 to 70 per cent reduction in the number of burrows in each area.
From next month, NEA will also step up enforcement in Town Council areas.
In the meantime, the experts advise that food spills and waste be cleaned up.
Bite marks on goods and food packaging, gnaw marks on electrical cables and urine on walls are all signs that rats are around.
Said Dr Chan: “It is important to build awareness and education around storage and waste management like food waste and cleanliness as well as proper disposal of bulky items.”