Burrow Baiting 101

Andy Knox from Bell Labs explains how to successfully bait rodent burrows.

Rodent control services produce some of the highest number of callbacks for pest managers, so a thorough inspection of the premises is essential to properly identify the species present and determine the control techniques to follow. One area to pay close attention to during an inspection, are harbourage areas where rodent burrows might be present. While typically associated with Norway rats, roof rats (the predominant rodent species in Australia), will often occupy burrows as well. Burrow baiting can be a very effective weapon in the war on rodents.

Where should I look for rodent burrows?

Rodent burrows are typically found along building foundations, in garden beds and in aerated or soft soil in lawns. Burrows are usually located within close range of food and water sources, so pay close attention to areas around the building. Roof rats can travel up to 400m from their harbourage sites, so a thorough inspection that begins outdoors and moves inside is critical in any account with a rodent infestation.

To determine if the burrow is active, look for rodent hair, droppings or signs of harbourage. The openings to burrows tend to be smooth and clear of vegetation if they are in frequent use.

What can rodent burrows tell me?

Rodent burrows can be an important clue in determining the size of a rodent infestation. By first determining the infestation severity and high activity areas, pest managers will be more equipped to handle the infestation and choose appropriate baiting strategies. Thorough inspections followed by proper bait and trap placements will lead to a reduced number of callbacks.

To determine the size of a rodent infestation based on rodent burrows, try this simple equation:

Estimated of number of rodents =

(Number of active holes x 8) divided by 3

If there is lots of food nearby, assume 20% more rodents, if food is not readily available, assume 20% less rodents. For example, nine active burrow holes can mean there are 20 to 30 rodents at the site.

How do I bait the burrow?

After a thorough investigation reveals the species and level of activity around the site, the next step is to properly bait the burrow. Dropping a bait block or a sachet down a burrow will commonly lead to it reappearing – where you don’t want it! Pelleted bait such as Bell Laboratories’ Ditrac pellets is ideal for placing in burrows, as it appears to a rat to be similar to seeds or other small foodstuff that might blow into the hole. Ditrac contains the powerful active ingredient, brodifacoum. It is the strongest, single-feeding anticoagulant bait on the market today.

Ditrac rodenticide is manufactured from an advanced formulation that produces a fresh tasting, highly compressed pellet, noted for outstanding acceptance. The hard pellet satisfies the rodent’s desire to gnaw, reducing bait shyness amongst neophobic roof rats.

When applying bait into an active rodent burrow, it is important to remember that the bait must be placed at least 15cm into the burrow so non-target species cannot access it. Try using a long handled spoon or a funnel attached to a length of flexible hose to ensure this is done correctly.

A funnel and tube can be used to deliver bait deep into a burrow

Should I close the burrow entrance?

After bait is properly applied into a rodent burrow, it is important to not disrupt the rodent’s habits by closing entrance and exit holes with soil. If rodents find a closed burrow, they will avoid the area and the bait will not be consumed. Secondly, the soil may fall into the runway and contaminate the bait. Leave the burrow holes open until follow-up inspections then use pieces of crumpled up paper to loosely stop the holes – this again appears to the rodent like something that can be wind-blown, is easy to remove – and doesn’t contaminate the bait. If the paper stays in place, you have probably controlled that population, if it is removed, repeat the baiting process!

Ditrac rodenticide in action

Bell’s Ken Parry was recently called in to a tricky rodent job at a well-known sailing club in southeast Queensland. Rats were a major problem around the kitchens and refuse areas, and the local pest manager was struggling to gain control. Ken suggested that the company try Detex Blocks – a monitoring bait that is highly palatable and contains a luminescent dye that makes the rats faeces glow in the dark.

The Detex was placed in bait stations around the problem areas – and was taken up very quickly by the rats. An inspection at night, with a blacklight torch showed that the rodents were living in amongst the rocks of a nearby sea wall (main picture, above). Not only that, but it showed clearly which amongst the thousands of holes were the ones that the rats were using. From there it was a relatively simple task to bait appropriately, and a successful result was achieved.

Andy KnoxAustralasian Business Manager, Bell Laboratories

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