THE number of rat infestations in the Ryedale area has risen by 25 per cent in the past year, leaving pest control services at full stretch.

Environmental health officials say many of the complaints relate to rats getting into houses, and are urging residents to block up any gaps around pipes.

Ryedale District Council has received more than 500 calls from householders since last March, an increase of 25 per cent compared to the same period in 2004.

The number of calls does not seem to be slowing.

Steven Richmond, the authority's environmental health manager, said: "We are receiving on average ten calls per day about rats. The worrying thing is that many more of these complaints concern rats getting inside the properties than other years."

The unprecedented number of calls has left the authority's pest control service operating at full tilt.

Mr Richmond said certain calls were having to be prioritised over others.

"While the service is coping with the situation, residents are asked to be patient if officers cannot attend within the normal response time of the next working day," he said.

"The situation in Ryedale is reflected in national trends, which show increases in the rat population.

"The increase in rats is probably due to a number of factors, including a succession of mild winters extending the breeding cycle, wetter winters forcing the rats to seek shelter, increased costs of rat bait and subsequent under-baiting and an association with wild bird feeding and domestic pet feeding."

He advised residents to make sure they examine the outside of their properties and fill in any gaps around pipes that go in through walls.

Climbing plants such as ivy should be cut back to well below gutter level to prevent access to rodents. Any broken air grates should be replaced and any damaged drains or manhole chambers fixed.

Birds should be fed using feeders, or by leaving food in containers on bird tables. Small amounts of food should be left more often rather than large amounts in accessible positions.

Any pet food stored in outhouses should be kept in lidded metal bins.