Rat baiting is being carried out to deal with a colony of "well over 100" of the rodents around the Therfield Heath car park opposite Royston McDonald's.

The Conservators of Therfield Heath and Greens said they have authorised the placing of rat poison in secure bait boxes which are then placed within the litter bins' bases.

"This has significantly reduced the risk of any human contact with the bait," said the conservators chair Clare Swarbrick.

"However, we are warning all users – particularly dog walkers – to be alert. Keep young children and dogs close to you and within eyesight to ensure that they do not come into contact with rats/rat remains in this area.

"Additionally, we will be removing some bins (which have been damaged by the rats) so as to limit rat access to food waste and to give our pest controller the greatest chance of bringing this problem under control in the coming weeks. Please play your part and take food waste home with you."

Concerns have been raised about the bromadiolone poison and the impact on wildlife. They have posted on Facebook and on their website informing residents of the process, and explaining that the move was not taken lightly. The full post includes links to correspondence with NHDC and information on the law around pest control.

On their website, the conservators said: "The last few months have been incredibly challenging for the heath and the car parks with increased foot fall and litter.

"It is therefore not surprising, yet is most regrettable, that we have found that we have a growing rat colony in the small and very well used Therfield Road car park.

"We are required to take action by North Herts District Council under the Pest Act 1949 because of the risk to humans from the infestation. "

"Given that notice under the 1949 Pest Act has been served we need to take action. Our pest controller estimates that there are well over 100 rats within the car park.

"Rats can breed at a prolific rate. An online search will highlight some of dangers that rats pose to humans.

"We have not taken the decision to use rat poison lightly. We have taken this decision after the receipt of notice from NHDC under the Pest Act 1949 and upon receipt of professional advice from a pest controller.

"We have communicated widely and successfully with the dog trainer, dog walker and dog owner communities. For those who were not contacted in advance, or by the time that baiting started, then there are many onsite signs to alert dog walker and also any casual visitors.

"We think there will be few pet cats in this area as it is a significant distance from any houses and in any case we would hope cat owners would not allow their pets to hunt or explore in a nature reserve.

"We have engaged with local wildlife groups, and Natural England, and hope they will assist in ensuring our approach minimises any impact on wildlife.

"We will maintain the regular bin emptying and litter patrols and have arrangements in place to remove any rats/rat remains and for those to be disposed of correctly.

"Along with our pest controller we will monitor the infestation and we all remain ready to modify our approach. We will do all we can to minimise adverse consequences but must be responsive to NHDC and comply with the Pest Act 1949.

"We are obliged to provide regular updates to NHDC in respect of this matter and to comply with the terms of their letter to us which again can be seen here.

"We have a plan to upgrade the bins to versions that stop rats from getting into them. This will (we hope) reduce the availability of food once they have been delivered and installed.

"Although we have twice daily bin emptying and litter picking we note some litter/ waste and food is still being left on the floor by the public.

"We ask everyone to play their part and to take their litter home with them.

"Work with us to make Therfield Road car park rat free."

The Crow has contacted the conservators, North Herts District Council and more. Updates to follow.