The Case of the ‘Trojan’ Roof Rat

A frequent way pests gain access to otherwise soundly pest-proofed buildings is through incoming shipments.

The Sprague rodent management experts were recently engaged by a client – a vegetable processor – that was having a difficult time with a roof rat. How difficult?

Rodents hitching a ride in shipments from growers are common at fruit and vegetable processing facilities. But when the staff noticed a rat jump off a pallet on an incoming shipment it set off a two-week odyssey for the facility staff and technician.

They started finding rat droppings and evidence of eaten vegetables inside almost daily and the processor was throwing out thousands of dollars of damaged product. It raised the degree of difficulty for the plant’s QA manager as ownership issued a mandate – eliminate the rat.

The facility – located in the suburbs of a major metropolitan area – had no previous record of rodent captures or sightings inside. There was no adjacent rail line to the structure and there was normal landscaping on the exterior.

After two weeks trying to get the issue under control and armed with a growing file of evidence that a rat was indeed inside the facility, a Sprague QA manager accompanied the technician on the next service call.

Upon arrival the Sprague QA manager noticed a large storage rack – two pallets deep and three tall – near the refrigerated processing area where produce – squash in this case – was brought in on forklifts and stored until it was processed. The rack held six to 10 pallets – none at floor level – that were brought in and out frequently as incoming shipments arrived.

Thinking the culprit was a Norway rat, the young technician placed traps at the base of the rack in effort to remedy the situation. It was assumed the rat was climbing the racks at night and eating the vegetables but not living in the storage tubs.

After the client had again found damaged produce in one of the tubs, Sprague’s QA manager recommended they take the tubs outside and inspect them.

The client took the tubs out on a forklift and in the first one that was unloaded they found a roof rat living inside. It turns out the rat indeed had living quarters in the tubs.

Once inside it had no reason to leave since there was a readily accessible food source and it was free to forage different areas of the plant at night.

Lessons Learned

• Never assume pests are gaining access to your facility in the most obvious way – open doors and windows, or openings in the foundation. Yes, pests will take the easy way in but as we learned in this case, they’ll also be a little sneaky about it.
• Work with your pest management service provider to examine all the possibilities and use technology to help. Sprague is deploying more cameras and remote monitoring devices inside facilities to track rodent movement.
• Roof rats are particularly challenging since they can go their entire life without touching the ground and away from floor mounted traps and mechanical devices. That’s why their preferred choice of harborage and entry can be high atop storage racks, and in exposed beams and false ceilings.
• Train your shipping and receiving managers to thoroughly inspect incoming shipments. Look for evidence of rodents in the trailer, in the tubs and pallets – take nothing for granted. If you see a few droppings don’t assume they’re from a previous load – act. Reject the shipment or unload it away from the facility (if possible) to avoid having rodents pull a ‘Trojan horse’ and gain access to your facility.

For more information on how Sprague can assist you manage rodent issues in your facility, call 855.805.0755 or visit our commercial services page.