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721 Mice and Rats Eliminated in One Month: An Environment-friendly Deratization Project for Coral Reef Islands

[Provided by the Department of Oceanography] Mouse and rat infestation is prevalent in the Dongsha Atoll National Park, which boasts a beautiful coral reef ecosystem. In response, the NSYSU, Marine National Park Headquarters, and Coast Guard Administration based in Dongsha Island (e.g., Dongsha-Nansha Branch) collaborated in the large-scale Environment-friendly Deratization Project. Within only one month, 721 rats and mice have been captured and eliminated.

Keryea Soong, a professor at the Department of Oceanography, NSYSU, pointed out that these mice and rats are not native to Dongsha Island and instead were brought to this island by ships. In addition to the fruits of screwpine (Pandanus tectorius) and Alexandrian laurel (Calophyllum inophyllum L.), the mice and rats feed on the food leftover by humans. Their habitat is not limited to the forest but largely overlaps with that of humans. They may also affect other terrestrial animals. For example, sightings of brown booby (Sula leucogaster) in Dongsha date back to 1867. However, these birds become rare today, possibly due to increasing human activities and the introduction of rats, which might have consumed the eggs of these birds.

With a project sponsored by the Ministry of Science and Technology, the team led by Soong has devoted efforts to both conducting scientific research and maintaining the Dongsha Atoll Research Station. In the Environment-friendly Deratization Project, the team employed powdered corn cob, which is rich in fiber, as a component of the formula for the effective culling of mice and rats. Fiber cannot be digested in the intestines of mice and rats and will block their intestines without causing them to vomit. When rats ingest powdered corn cob, the ingested fiber absorbs a great amount of water in their intestines, leading them to die from dehydration. Such edible fiber is not toxic to other animals.

“This is an environmentally friendly method of mouse and rat culling,” Soong emphasized, “and countries in the European Union have also permitted the use of powdered corn cob as environmental bait for toxic killing of rats and mice.” The team’s tests showed that mice and rats were particularly attracted to powdered corn cob mixed with 20% to 40% powdered peanuts, and died in 3-5 days following consumption of the bait. The powdered bait cannot be spread directly onto the ground; rather, it should be wrapped in a paper bag. This protects the bait from moisture and makes it easier to be carried by the rats and mice. This would enhance the possibility of the bait to be consumed in the nest of these animals.

Between December 2019 and February 2020, the Environment-friendly Deratization Project has contributed to the elimination of 1043 mice and rats. The team has been improving the formula and placement of the bait, aiming to extend its use on Taiping Island, Tern Island in Mazu, and other ecological islands of Taiwan.

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