NPUST study: Over 60% of raptors tested positive for rat poison, black kites and Crested Serpent Eagles affected

A sickly black kite (Milvus migrans), stripped of its soaring glory, lay at the NPUST Wildlife Rescue Center with its beak weakly opening and closing. A veterinarian on hand urgently administered an antidote injection and IV fluids, but after the rescue effort, the black kite still could not return to the skies and died needlessly on the cold examination table.

This black kite, which died needlessly in Donggang in 2013, was later sent for testing. The report results showed that rat poison was detected in the carcass, with the ingredient Brodifacoum, and a veterinary necropsy confirmed internal bleeding. The NPUST Bird Ecology Research Lab (hereinafter "NPUST Bird Ecology Research Lab") confirmed that this black kite was the first raptor in Taiwan's bird research records to die from rat poison poisoning.

The death of this black kite launched a large-scale investigation into rat poison residues in Taiwan's raptors, jointly undertaken by the Bureau of Animal and Plant Health Inspection and Quarantine (BAPHIQ), which invited the NPUST Bird Ecology Research Lab, the Endemic Species Research Institute, the Taichung Wildlife Conservation Society, and the Roadkill Club, among others. In total, liver samples from 21 raptor species and more than 200 specimens collected from across Taiwan between 2010 and 2018 were tested. The results showed that 10 raptor species and over 60% of samples tested positive for rat poison residues, indicating that rat poison has widely entered Taiwan's ecological food chain. The research paper was published in 2019 in the authoritative environmental science journal Science of The Total Environment.

NPUST black kite study: anticoagulant rat poison causes bleeding

The NPUST Bird Ecology Research Lab began black kite research in 2011 and later received poisoned black kites one after another, which led them to try different testing items to confirm the cause of death. "A raptor gets poisoned through its food." Lin Hui-shan, a researcher at the NPUST Bird Ecology Research Lab, pointed out that relevant tests are determined based on the raptor's food source, including tests for pesticides, rat poison, banned aquaculture drugs, and even heavy metals and other residues.

"Since no pesticides were detected in the Donggang black kite in 2013, and it had symptoms of bloody stool and stomach bleeding, we suspected whether it had eaten a poisoned rat? Whether the anticoagulant ingredient in rat poison caused the internal bleeding?" said Hong Hsiao-yu, first author of the paper and a researcher at the NPUST Bird Ecology Research Lab.

Rat-eating snakes poisoned in turn, raptors die from unstoppable internal bleeding

All rat poisons currently approved in Taiwan are anticoagulants. After poisoning, they destroy the blood-clotting function in the body, so bleeding will not stop, including oral bleeding, subcutaneous hematoma, and anemia. The internal organs of poisoned animals will gradually bleed, and they die only after about 5 to 10 days, making it a chronic poison.

The lab found that raptors that feed on live rats, decaying rat carcasses, or mainly snakes are at high risk of rat poison poisoning. Among the 5 raptor species commonly seen in plains and low-altitude areas, the Black-winged Kite, which mainly eats rodents, had a rat poison detection rate as high as 90%, and also had the highest average detected concentration (0.211 ppm). In addition, the black kite, which has the habit of eating animal carcasses, and the Crested Serpent Eagle, which mainly eats snakes, ranked second in detection rate and average concentration, respectively, indirectly proving that snakes that feed on rodents may be one of the important links transmitting rat poison through the food chain, causing Crested Serpent Eagles to be poisoned as well.

As for the Crested Goshawk and Collared Scops Owl commonly seen in rural and urban areas, although they eat rats, they have a broad diet, yet their rat poison detection rates also both exceeded 50%.
The detection rate and concentration of rat poison in raptors were highest in autumn and winter. The lab inferred that this may be related to Taiwan's annual autumn Rat Extermination Week. The agents distributed during Rat Extermination Week are mainly second-generation agents Brodifacoum and Flocoumafen, which are the ingredients most often detected in raptors. Another common rat poison ingredient, Bromadiolone, is mostly registered as an environmental pesticide, so it is not only an agricultural pesticide; household environmental pesticides also enter the food chain.

A single Crested Goshawk had as many as six kinds of rat poison in its body, wildlife suffering greatly

Rat poisons approved in Taiwan after 1980 are almost all second-generation rat poisons. "Besides being more toxic, they also accumulate in the body for longer." Hong Hsiao-yu pointed out that second-generation agents take more than 200 days to naturally metabolize in a rat's body, during which they are easily passed along and accumulated through the food chain. The study found that many raptors tested positive for more than one rat poison ingredient. One Crested Goshawk once had as many as 6 kinds of rat poison in its body, meaning it had repeatedly eaten rats carrying different agents.

Besides raptors, other wild animals that prey on rats, such as Grass Owls, leopard cats, and snakes, may also suffer greatly, and even ordinary small animals such as squirrels, masked palm civets, cats, and dogs may die from accidental ingestion. Hong Hsiao-yu added: "In fact, there are still very many pathways that spread rat poison. For example, farmers often mix the agent with some grains to lure rats, but small birds, and even insects, slugs, and snails may all eat these mixtures, and then they are eaten by predators (and thus carry rat poison in their bodies)." Therefore, in the ecosystem, the transmission pathways of rat poison are extremely diverse.

Asia's first study; Taiwan had not conducted testing before

The ecological harm of rat poison has been confirmed by many studies in Europe and the United States, and restrictions on rat poison use have already begun. Yet this study was Asia's first screening study on rat poison residues in raptors. "Rat poison has been used for so long, and only in recent years has the problem of raptor poisoning begun to be discovered, because Taiwan never conducted testing before."

Hong Hsiao-yu explained that confirmed cases of raptor rat poison poisoning have only emerged in the country in recent years. On one hand, after being poisoned, raptors may be hit by cars or attacked by natural enemies because of weakness and slowed movement, so the cause of death is misjudged; on the other hand, testing is expensive, and there are few applications requesting tests for rat poison residues, so most testing centers do not stock rat poison standards and cannot perform quantitative testing. Beginning in 2013, the NPUST Bird Ecology Research Lab was able to purchase standards for testing with funding from bird lovers.

The seasonal trend of raptor poisoning is consistent with the government's Rat Extermination Week activities

The study also showed that the seasonal trend of raptor poisoning is consistent with the government's Rat Extermination Week activities. Since it began in 1979, Rat Extermination Week has been held for more than 30 years. Each year, a time after the late-autumn crop harvest is chosen (roughly October to November), when the government distributes rat poison free of charge. One consideration is that the dry season has less rain, so the rat poison will not become damp; another is that rats lack food at this time, so poisoned bait can wipe out field rats in one sweep.

But reviewing the principle of distributing rat poison during Rat Extermination Week, Hong Hsiao-yu pointed out that in fields without crops, there would originally be no agricultural damage, and the effect of the placed poison in killing rats cannot last until the next year. "Rats reproduce very quickly. After poisoning the rats, it takes only 2 or 3 months for the rat population to recover. By then it is already spring, and crops are being planted again."

Taking into account that crop planting times vary across regions, and responding to suggestions from bird conservation groups, BAPHIQ avoids field rat control work during the bird breeding season and has gradually adjusted its farmland rat control policy. This includes announcing in June 2015 the cancellation of the "National Rat Extermination Week" that had been implemented for more than 30 years, abolishing a uniform control period across all regions so that the space and time of rat poison placement can be dispersed; and from 2016 onward no longer subsidizing rat poison, and in 2018 canceling the joint supply contract, allowing county and city governments to procure on their own according to need.

BAPHIQ urges farmers to collect rat carcasses to prevent accidental ingestion by raptors

BAPHIQ also urges local governments and farmers to reduce or stop using pesticides in agricultural areas where raptors frequently appear, and to promote correct ways of using the agents, such as applying the agent before and in the early stages of crop planting, placing the agent in plastic cans or bamboo tubes to prevent accidental ingestion by non-rat organisms, and patrolling fields to collect rat carcasses to prevent scavenging raptors from picking them up and eating them.

"Policy adjustments can change some of the current situation, and production and ecology can both win." The Plant Protection Division of BAPHIQ pointed out that because this policy is supported by scientific data and is implemented gradually, it has so far not received major reports from farmers of rat damage to crops, and the number of black kites in surveys in recent years has also clearly increased, from 272 in 2013 to more than 500 in the past 2 years, which is also good news. In the future, new control technologies or safer rat baits will also be introduced, such as agents containing plant fiber; after rats eat them, the fiber expands upon contact with water and blocks the gastrointestinal tract, causing them to "burst to death," and this ingredient will not poison raptors or other organisms.

Although farmland rat control policy is gradually returning to local control, BAPHIQ will still continually review related policies. For example, to improve the safety of rat bait use, BAPHIQ has revised the methods for using rat bait, requiring anticoagulant rodenticides to be placed in bait stations for application, and prohibiting processed raw materials or technical materials from being retailed in finished form. It has also revised the packaging to add additional cautionary wording, including that poisoned bait should be properly stored, and that in case of accidental ingestion and poisoning, the person should be sent to a hospital for emergency treatment, with vitamin K used as an antidote.

Poisoning rats also kills their natural enemies, which will cause rat populations to surge

"Poisoning rats also poisons rats' natural enemies. Rats reproduce very quickly, so their numbers can bounce back quickly, but natural enemies generally reproduce very slowly, so once the natural enemy population disappears, it is very difficult to recover, causing the ecosystem to lose balance -- the rat population surges before long, and with no natural enemies to suppress them, farmers use even more rat poison to suppress these rats, creating a vicious cycle -- they must repeatedly use poison but can never poison them all!"

Hong Hsiao-yu said that to break the vicious cycle, farmers must combine other measures, such as placing rat traps. In recent years, the lab has also advocated that farmers can use biological control methods of "one thing subduing another," replacing rat poison with raptors preying on rats, such as making owl nest boxes and Black-winged Kite perches.

As for perches, there are currently about a dozen sites across Taiwan, visible in places such as rice paddies in Wufeng, Taichung; fields in Meinong, Kaohsiung; and pineapple fields along the Pingtung Coastal Highway. The lab also provides teaching services. Hong Hsiao-yu said: "The principle of erecting perches in fields is to use raptors' habit of liking to stand at high points to attract Black-winged Kites into the field area to perch and hunt, thereby reducing rat damage."

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