18 September 1998

Plan tight strategy to combat soaring rat population

By John Tearle

RATS are a real public enemy; in the interest of public health, safety in the workplace and to prevent losses on the farm control must be a top priority, urges Adrian Gray of rodent specialist Sorex.

"The success of rats as a species and why they pose such a problem to man is that they breed at such a fantastic rate," says Mr Gray. "A female rat is sexually mature within two to three months, and can have up to seven litters a year with eight to 10 young at a time.

"Rat numbers are often wildly underestimated as rats are shy, mainly nocturnal animals. It is said, that for every rat seen during the night there is probably a dozen unseen, and for every rat seen during the day there could be more than 100 in the background."

"It is this phenomenal breeding rate and natural shyness that must be taken into account when deciding on a rat control programme. Eradication is not viable. A systematic control programme is the only option."

Rubbish, debris and overgrown vegetation should be completely removed from around buildings. Inhibit access to buildings using metal cladding at the base of doors, mesh on air vents and block all holes.

Successful baiting then hinges around a co-ordinated strategy. "Make a plan and mark on it areas of rat activity. You must find out where they are living and feeding. While rats may not be visible, signs of their presence will be. Look for burrows, runways, smears, droppings, tracks and signs of gnawing, and identify points of entry into buildings. Rats will travel as far as 100m for food, so your survey must cover at least this distance," explains Mr Gray. "Use this plan to determine where to place bait stations."

To clear a rat population place bait stations beside rat runs between nesting and feeding sites, beside runs around buildings and at sites of entry, he advises. Place baits in holes and nesting sites and inside buildings where droppings are seen. Use purpose designed containers where possible, and always protect them from the weather and other animals and birds. "Good cover of the bait helps the rat to feel safe so it will feed for longer."

Failure to control rats often occurs because insufficient bait is put down and is not replaced once eaten, Mr Gray says. A good number of baiting stations is needed and they need to be inspected regularly, especially in the first two weeks. Replace eaten bait and do not stop baiting until feeding has stopped. A rat needs to eat 10% of its body weight in poisoned food over a three to four-day period to take a lethal dose.

Successful control is indicated when baits are no longer taken.

Establish semi-permanent baiting stations on likely approach routes to guard against reinfestation by another colony. Check these every two to three weeks. If signs of rat feeding are found, replenish the bait and then check if rats have penetrated defences. &#42

CONTROL AND PREVENTION

&#8226 Identify where they live and feed.

&#8226 Identify pathways to food.

&#8226 Place baiting stations along pathways.

&#8226 Check baiting stations regularly and replenish until no more bait is taken.

&#8226 Remove rubbish and debris from around buildings.

&#8226 Stack feed in bags or boxes on pallets off floor.

&#8226 Sweep up spilt feed or grain.

&#8226 Put rubbish in closed containers.

COMMON TYPES OF BAIT

&#8226 Ready-prepared cut grain: Use as standard in most bait stations.

&#8226 Bait Blocks: Ideal for burrow baiting or in semi-permanent bait stations. No spillage.

&#8226 Sealed plastic sachets: Ideally suited in semi-permanent bait stations.

&#8226 Pellets: For use in grain and other food stores inside a fixed baiting station where a more palatable bait is required to get the rats to feed.

RAT TELL-TALES

&#8226 Burrows in soil, under rocks and broken concrete, especially near water.

&#8226 Runways. Pathways in grass and vegetation and along walls. Greasy trails at the margins of walls inside buildings. Ledges where dust and cobwebs have been brushed off.

&#8226 Smears. Rats like to move with their bodies in contact with solid objects leaving greasy stains.

&#8226 Droppings. Rat droppings are cylindrical shaped, 15mm long and 5mm wide. They are bright and shiny when fresh. Different sized droppings indicate a breeding colony – rapid action is vital.

&#8226 Gnawing. Often seen at entrances to buildings or on packing cases, cables and pipes.

&#8226 Tracks. Footprints can be seen in mud or dust. Do not confuse with those of birds.

Rising rat numbers demand greater attention to bait formulation – cut grain or pellets – (left) plus the sighting and regular checking of bait dispensers (above).