At a pig farm where conventional control measures had failed to reduce rat damage, an evidence-based trial using repellent devices was conducted. This case was reported by Hiroyasu Yamada, Yoriko Sakamoto, and colleagues at the Chiba Central Livestock Hygiene Service Center. Its defining feature was an approach built not on "killing" rats, but on making the environment inhospitable — drawing on an understanding of rat behavioral instincts.
This section presents the details and outcomes of that initiative in a format that can be practically replicated in the field.

The farm had been applying coumarin-based rodenticides twice a year as its standard control measure. However, the damage showed no improvement and rat activity continued unabated.

Situation at the Time

• Rodenticide applications were not reducing population numbers
• Any effect observed was only temporary
• Reinfestation occurred quickly after each treatment

Furthermore, the farm owner had a strong preference against placing rodenticides near pillars, walkways, or any areas accessible to pigs, out of concern that pigs might accidentally ingest the chemicals.
This is a critically important point.
Even when a measure is theoretically effective, it may be "unusable" or "impractical" in real-world conditions.
In other words, there is a real gap between "what works" and "what can actually be used."
Within these constraints, the need arose to find a solution that did not rely on chemical agents.

Devices were first installed in a single pig pen as a trial, and nocturnal behavior was observed using an infrared camera.

Observed Responses

• Rats approached the repellent devices
• Stopped partway through
• Turned around and retreated

In other words, a clear "cannot pass" and "do not want to go further" response was observed.
At this stage, it was confirmed that "Rat Repellent Device Z" functions as a physical barrier and also produces a psychological deterrent effect.

Based on the trial results, a total of 2,000 repellent devices were installed in the piglet barn and fattening barn in April 2004.

Immediate Responses After Installation

• Rats colliding with the devices
• Running about in a panic
• Emitting squealing-like vocalizations

Rats were observed entering a temporary state of agitation and panic.

However, when population numbers were checked one month later, no significant change was observed.
This is a critically important point in this case study.

• Repellent devices alone cannot "drive rats out"
• Repellent devices alone cannot "reduce numbers"

This reality became clearly apparent.

It was therefore determined that the repellent devices alone were insufficient, and a multi-pronged approach was implemented.

Measures Implemented

• Installation of glue traps
• Flushing rats out using a power sprayer
• Cleaning and disinfection of rat habitation areas
• Additional installation of repellent devices (approx. 700 units)
• Installation of iron barrier plates
• Limited application of rodenticide in attic spaces

These measures were implemented simultaneously and in combination.
The key here is the sequence:

1. Drive rats out
2. Remove dirt, odors, and traces
3. Use repellent devices and barrier plates to prevent re-entry

In other words, establishing a continuous cycle of "drive out → reset → block re-entry" was what made the approach effective.

Fixed-point monitoring using infrared cameras confirmed the following clear improvements:

• Number of rat sightings: reduced from 121 to 41
• Droppings scattered on floors and walkways almost completely eliminated
• Feed contamination with droppings also resolved

Rather than rats simply becoming "less visible," a measurable, quantified reduction was confirmed — which significantly strengthens the credibility of this case study.

The most important conclusion from this case study is that "Rat Repellent Device Z" itself demonstrated a clear and measurable pest control effect.
Even during the trial installation phase, rats were observed hesitating to approach the devices and turning back — confirming that "Rat Repellent Device Z" is an effective tool for suppressing rat behavior.
Following full-scale installation, rats were seen colliding with the devices, fleeing in distress, and emitting squealing-like calls — indicating that the devices were successfully creating a highly stressful environment for the rats.
This demonstrates that "Rat Repellent Device Z" is a practically effective material that directly influences rat behavior.
At the same time, in this particular case, the control effectiveness became most apparent when the repellent devices were combined with additional measures such as flushing, cleaning and disinfection, and the installation of barrier plates. This is best understood not as compensating for any shortfall in the devices themselves, but as completing a strategy built around "Rat Repellent Device Z" as its central component.
In other words, "Rat Repellent Device Z" is valuable on its own, and combining it with complementary measures allows its effectiveness to be maximized.
Because rats are highly intelligent learners, half-hearted measures will quickly be adapted to. However, by creating an environment that rats cannot return to even when they try, long-term prevention of infestation becomes achievable.

The key insight from this case study is that rat control is not something that can be completed in a single effort — continuous management and ongoing refinement are essential.
Unless livestock farmers themselves develop a strong awareness of rat prevention and continue to refine their day-to-day management practices, effective rat control is difficult to sustain.
In particular, from the perspective of protecting food safety in production facilities, rat control is critically important.
Since rats can transmit pathogens, eliminating potential sources of infection is a fundamental element of ensuring the safety of livestock products.

This study confirmed that "Rat Repellent Device Z" has a measurable pest control effect.
Even in locations where rodenticides cannot be used, or where chemical treatments have not proven sufficiently effective, "Rat Repellent Device Z" represents a practical and viable control option for use in the field.
The key is not to rely on any single measure, but to select methods suited to the specific conditions of each facility and maintain them consistently.
"Rat Repellent Device Z" can serve as the cornerstone of such an approach — a strong and reliable option for supporting an ongoing, sustainable pest control system.
Building on this field study, the next article will introduce the principles behind effective rat intrusion prevention and offer concrete practical proposals.