August 28, 2003: The day Tonnie Casey had awaited for years was at hand. Finally, she was going to supervise the helicopter drop of tons of pellets containing rat poison across hundreds of acres of land at Keauhou Ranch, near Volcano, Hawai’i, owned by her employer, Kamehameha Schools/Bishop Estate.
Three months earlier, in May, Casey had received the blessing of the Environmental Protection Agency to go ahead with the aerial broadcast of the pellets containing a 0.005 percent (50 parts per million) concentration of the blood-thinning agent known as diphacinone. The experimental use permit that the EPA granted was to sanction the first widescale field test in Hawai’i involving the distribution of rat poison by helicopter. The technique had been used successfully in New Zealand to control rat populations in habitats for rare and endangered birds. Casey herself, trained as a helicopter pilot during a stint with the U.S. Army, had participated in a New Zealand trial and for years had led a growing chorus of zoologists and other researchers in Hawai’i who wanted to add this method to their arsenal of weapons available for use in the battles to protect Hawaiian birds.
This was not the first time an aerial drop of rodenticide had been done in Hawai’i. In 1999, Casey supervised a drop of 1,050 pounds over 70 acres of forested land at Keauhou Ranch. Other, even more limited, trials had been conducted on federal and state lands. The 2003 experiment, however, was to cover 800 acres, far more territory than in any previous experiment.
When the helicopter lifted off that morning from Keauhou, it carried aloft not only a couple hundred pounds of Eaton’s Bait Pellet Rodenticide with Fish Flavorizer, but the hopes of the entire community of scientists, researchers, and wildlife and forest managers working to save Hawai’i’s rare birds and plants from extinction. If this worked, they thought, it could be the long-sought silver bullet needed to eradicate one of the forest birds’ chief predators and to enhance prospects for survival of rare plants as well.
Half a year later, those bright hopes for quick approval of aerial broadcasts of rat poison have run up against further delays that have put a cloud on the whole enterprise. Instead of the Keauhou experiment marking the beginning of a new era for predator control in Hawai’i, it has rather set back the cause for months and, more likely, years.
A Glitch
The day dawned bright and sunny. An employee with the Hawai’i Department of Agriculture, charged by the EPA with supervising the experiment, was present “to make sure our paperwork was in order,” Casey wrote in a “Chronology of Significant Events” prepared for Kamehameha Schools.
After the helicopter had made several passes, something went wrong with the bucket that was supposed to distribute the pellets evenly across the landscape, recalls Jack Jeffrey. Jeffrey, a noted wildlife photographer, had taken the day off from his job as a biologist with the Fish and Wildlife Service so he could record the historic occasion on film. “They had bucket problems,” Jeffrey told Environment Hawai’i. “They flew the helicopter to the national park” – Hawai’i Volcanoes National Park – “and the park did repairs.” Flights ceased for the day by 2 p.m., when fog made it impossible to continue safe operation of the helicopter.
The next day, the motor in the bucket broke again after the helicopter had made three swaths, broadcasting 600 pounds of bait. “We could not fix it on site,” Casey wrote, so the bucket was hauled into Hilo for repairs.
It was noon on September 4 before the experiment could be completed. “We finished the last 7 runs of 1400 pounds at this time,” Casey wrote. “Our total broadcast was 189-50 pound boxes of bait for a total of 9,450 pounds…. This rate of spread was 17.8 pounds per acre.”
To test the effectiveness of the bait drops, 69 rats in the treated area had been fitted with radio collars. (Casey’s surveys showed on average, there were between two and four rats per acre in the plots to be treated. Such low numbers are not typical, but resulted from several years of eradication efforts.) By September 9, Casey wrote, staff with the U.S. Department of Agriculture’s Wildlife Services, which was helping monitor results of the test, informed her that “there was evidence of 3 live rats in 3 of the 4 plots.” One goal of the experiment had been to kill all of the rats on the treated land, so that Casey could then determine how effective it might be to use less costly “bait stations” on the perimeter of a treated area to keep rats outside the area from moving in. “It is imperative to the integrity of the study that all rats in the area are dead,” she wrote. If some were still alive, she proposed additional bait drops on the rats’ home ranges. (The home range for a rat, Casey said, was about 200 meters square – or almost exactly one acre.)
The EPA experimental use permit allowed the rodenticide to be applied twice. Under terms contained in an EPA letter authorizing the experiment, up to 15 pounds per acre could be applied in the first round, with the remainder available, if needed, for a second application.
But the survival of the rats in the treated area was not the worst news Casey received that day, as she combed the Pu’u Lala’au paddock of Keauhou Ranch “with Rum (my trained Jack Russell Terrier).”
“While in the field looking for dead rats, one of the WS technicians told me that Pete Saverie [sic], the acting Hawai’i Field Station Leader, wanted to talk to me on the phone,” Casey wrote. At the time, Peter Savarie was acting head of the USDA Animal and Plant Health Inspection Service’s Wildlife Services National Wildlife Research Center office in Hilo. “It was then I was told that pigs were dying.”
Poisoned Pork?
In connection with Casey’s experiment, the National Wildlife Research Center had, in August, captured 10 feral pigs, fitted them with radio collars, and released them back into the area where the diphacinone bait was to be broadcast. By monitoring the pigs, researchers with the center hoped to be able to understand better what impact the bait might have on the pigs. Many of the forested areas of Hawai’i where the broadcast technique might be employed are open to hunting, and hunters for years had expressed their concern that the diphacinone used in the bait might find its way into the meat they and their families consumed.
After the experiment was completed, the radio collars would allow the pigs to be tracked down and killed by Wildlife Services personnel, who would also collect carcasses of non-collared pigs, if any were found, and hunt and shoot live pigs found in the treated areas. Tissue from all the animals would be collected and tested.
Casey expressed her pique at the delay in notifying her in the report she made to Kamehameha Schools: “This was day 12 after the first day of the broadcast and evidently they [pigs] had been dying since day 8. Unfortunately, everybody else was informed besides me, and the reporting period (24 hours) for adverse effects was already over. With more open communication this would not have happened. As a critical sidebar, this adverse effect, i.e., pigs dying, was not expected based on lab tests.” (Earlier in her report, Casey had mentioned laboratory tests of diphacinone on pigs, in which “it took 63 pellets per day at 7 days to make a pig sick.”)
According to a chronology prepared by Robert Sugihara, a wildlife technician with the National Wildlife Research Center’s Hawai’i Field Station in Hilo, on September 5, two of the radio-collared pigs had been recovered – one dead, one “lethargic.” On September 8, three collared pigs were found dead. A day later, Wildlife Services discovered two dead non-collared pigs, and on September 10, they recovered a total of five dead pigs (two with collars, three without).
By October 3, when Sugihara’s chronology ends, eight of the collared pigs had been recovered dead (or dying, in one case); one pig managed to escape its collar, so its fate cannot be known; and one collared 185-pound boar was tracked down, still very much alive, on September 15, when it was hunted and, to use the Wildlife Services’ term, “sacrificed.” Wildlife Services had also recovered five dead non-collared pigs and had hunted down six live non-collared pigs. In other words, within days of the rodenticide’s application, 13 pigs died, leading many involved to suspect they had ingested the poison bait intended for the rats.
Casey hazarded a guess as to why this might have occurred in her September 15 report. Between the second day of the experiment, August 29, and the third and final day, September 4, “Hurricane Jimena passed within 50 miles south of the Big Island and we got quite a bit of rain…. My belief is tropical storm conditions kept the rodents underground and thus pigs in the area ate the rodenticide.”
The wet weather should not have been unexpected. The same day the experiment began, Jimena had become a named tropical storm, with its predicted path coming close to the island of Hawai’i. By August 30, it had become a hurricane, and although it passed well south of the island, heavy rainfall associated with the storm was recorded from Hilo to Ka’u in the first two days of September.
But with a tropical storm in the forecast, the question arises as to why the experiment went forward at all. According to label instructions, the bait was to be applied only when “weather predictions call for less than 1/2-inch of rain over the next 3-5 day period.”
A Second Try?
At the time of her report, Casey still intended to conduct “very small aerial applications” of the rat poison to take out the last few live rats. “The state Pesticide Branch of DOA (Bob Boesch) agrees that this should be done to keep the scientific inquiry on course,” she wrote.
But in an email just two days later, Boesch strongly disagreed. “You requested my thoughts about several point drops to deliver diphacinone baits to rats that are active,” he wrote. “The taking of non-target animals was not expected based on the low LD501 and low concentration of diphacinone in baits. Given the problems with the hopper on the first trip and the amount of bait exceeding the 15 pound per acre limit for a single application (contrary to the conditions of the permit) and the fact that the rats are still alive, it is my opinion that a second drop of a much smaller quantity (maximum 2.2 pounds bait per acre) is not likely to kill the rats… To place even more bait will likely result in more non-target impacts and perhaps result in rats developing bait shyness. Point drops will likely exceed the limits of up to 20 pounds per acre.”
“Assuming that non-target kills were reported from the first drop of diphacinone rodenticide,” Boesch concluded, “the program believes a second drop without making necessary adjustments to reduce or eliminate non-target kills would violate the law and may result in an enforcement response.” Although the experimental use permit was issued by the EPA, the state Department of Agriculture had responsibility to oversee the experiment and ensure that it was conducted in full compliance with permit terms and conditions.
Casey had emailed her request to conduct an additional drop not only to Boesch, but to an EPA employee, William Jacobs, who had conducted a review of Casey’s application for an experimental use permit the previous April. Unaware of the concerns Boesch had raised in his email back to Casey on September 17, Jacobs told Casey, on September 20, “If you have poundage left (the difference between 16,000 and what you have used), you could make follow-up aerial treatments. If the use site is covered by the label for HI-970007, you also could use that product in bait stations.” (HI-970007 is the registration number for a bait block containing diphacinone that also is manufactured by Eaton’s.) Casey replied to Jacobs the very same day, thanking him for his “sound advice and superior thinking power.”
No one was talking in mid-April about what Casey did next. Casey said she had been instructed not to say anything and referred questions to Kekoa Paulsen, Kamehameha Schools’ public affairs officer. Paulsen could not provide responses to questions posed him by press time. Records obtained from the EPA do not contain any documents generated between September 20 (when Casey sent her reply to Jacobs’ positive email) and early November, by which time the state Department of Agriculture had launched an investigation into a wide range of issues surrounding this experimental use permit.
Did Casey use the pellets in the bait boxes, in accord with Jacobs’ suggestion? Boesch of the DOA’s pesticide branch in Honolulu said in mid-April that this question was part of the ongoing investigation and he could not comment. Yet a suggestion that she did just that crops up in an email of November 12 from Jacobs, who, when asked whether he had authorized use of the pellets in the bait stations, denies having done so, writing: “By the time that bait was applied in bait stations, it was known that feral pigs were in the area…”
Murphy’s Law
As head of the DOA’s pesticide branch office in Hilo, Glenn Sahara was assigned to investigate what went wrong at Keauhou Ranch. While Casey may have taken comfort in Jacobs’ “superior thinking power,” Sahara was evidently alarmed by it. In an email to Jacobs on November 10, Sahara asked what Jacobs meant when he suggested Casey could use the product in bait stations if it “is covered by the label for HI-970007.” Was the product Jacobs referred to the leftover pellets? Sahara asked. Or was it bait blocks, the product registered under the HI-970007 number? Sahara noted that the bait stations are intended to hold only bait blocks, since “the bait pellets are easily shaken out of the bait stations.”
In the EPA’s system of pesticide registration, every legal pesticide product is assigned a unique registration number. And for every registered pesticide product, there is a label that sets forth the conditions under which the product may be used. To apply a product in a manner other than that specified by the label is a violation of federal law. It is just as serious a violation to mislabel a product – for example, to put a label on pelletized rat bait (such as Casey was using) identifying it as a bait block.
In 2002, Eaton’s had shipped 16,000 pounds of pellets, in 50-pound boxes, to Kamehameha Schools. Each box bore the label for HI-970007, identifying the contents as “BAIT BLOCKS” in large letters. Whether the early shipment was legal is yet another question that, according to Boesch, is under investigation. At the time of the shipment, the pellets were not authorized for use and would not be for another five months.
In September 2003, however, Jacobs probably had no way of knowing the labeling problem when he sent his email to Casey, suggesting she might use HI-970007 in the bait stations.
In reply to Sahara, Jacobs wrote that he thought it was clear that he had been referring to bait blocks, since that was the product covered under the registration number. He continued, “If what Ms. Casey had received as ‘HI-970007’ was a pelleted bait rather than a bait block, however, that is what she would have thought it would be OK to use in bait stations. Whether or not she might have requested pellets rather than blocks, the registrant would have been guilty of supplying the wrong product as HI-970007.”
‘Hot’ Spots
After the pigs began dying, there was a general reluctance to believe that the deaths could have been caused by ingestion of rat poison that contained just 50 parts per million of diphacinone. As Casey noted, in one laboratory trial, it had taken several hundred pellets fed over the course of a week just to make pigs sick. Those results generally were in line with what was known about the way diphacinone is absorbed by mammals. One large dose in a short period of time (i.e., a day or two) is not regarded as nearly as harmful as a series of lower doses received over longer periods.
In a 1999 proposal to test Ramik Green(tm) (pellets with the same concentration of diphacinone as the Eaton’s bait tested at Keauhou Ranch), the National Park Service stated that, “Under field conditions, rats must consume a sublethal dose for six straight days to die.” That same proposal discussed the potential for harming pigs as well (although no pigs were in the areas to be treated in the Hawai’i Volcanoes National Park proposed experiment): “No residues of diphacinone were found in the muscle tissue of pigs fed diphacinone for 2-5 days at levels representing 120 to 300 pellets per feeding. Diphacinone was found in the liver but at such low levels that 10 tons of liver would need to be consumed to attain just the human therapeutic dosage.” (Diphacinone was originally developed as a blood-thinning agent and is similar in its effects to Warfarin, another rat poison often used as a human pharmaceutical.)
Could the pigs at Keauhou have received lethal doses of diphacinone if the concentration in the pellets was just 0.005 percent, as specified in the pesticide formulation?
Many of those involved with the Keauhou test speculate that the pellets must have been “hot” – that is, they must have contained higher than allowed levels of diphacinone to cause the pigs to die. Laboratory tests have been done to determine the concentrations, but none of the results was provided to Environment Hawai’i by press time. Peter Simmons, a land manager for Kamehameha Schools, said that he had been informed that three different laboratories came up with three different conclusions: one reported concentrations in excess of those allowed, another showed the concentration was right on the money, and a third showed levels of diphacinone so low as to be utterly ineffective.
Yet could the pigs have eaten enough bait to become sick, even supposing the concentrations of poison in the bait were spot-on at 50 parts per million? The math is suggestive.
By the Numbers
The aerial applications at Keauhou left 17.8 pounds per acre (on average) on the ground, according to Casey. When she did a “calibration” drop before the experiment on a 13-acre plot, she reported that the 200 pounds of bait dropped contained about 7,000 pellets, for an average of 35 pellets per pound. During the test, 9,450 pounds of pellets were dropped. Using Casey’s figure of 35 pellets per pound, that comes to 330,750 pellets. If they were evenly distributed over the 530 acres that Casey says were treated, there would be about one pellet in every six square meters (or .153 pellet per square meter).
Sugihara and his technicians conducted surveys along transects in all four plots that Casey had said would be treated in her experiment design. The total area surveyed by Sugihara came to 746 acres, not 530. He found many more pellets than one might have expected. While it’s true that some areas will inevitably receive more pellets than others in experiments such as this one, the transects should average out, with the areas receiving more pellets balanced by those receiving less than the average.
In each plot, Sugihara counted pellets along four transects; each transect consisted of 20 one-square-meter stations. That meant a total of 320 stations in the four plots were monitored. Mean (average) pellet densities ranged from a high of .80 pellets per square meter (Plot 2) to a low of .32 pellets per square meter (Plot 6). (A total of six plots were included in the experiment design: four – plots 2, 3, 5, and 6 – were to receive pesticide applications; two – plots 1 and 4 – were control areas.) As for the densities in the individual transects, just two transects (out of 16) had mean pellet densities at or below the level of .15 pellets per square meter. The remainder had densities as high as 1.85 pellets per meter (recorded on Transect B in Plot 5).
If the mean densities recorded on the transects were reflective of the total bait distributed during the aerial drops, the amount of bait that would have been applied is more than five times that reported – 49,483 pounds versus 9,450.2
Sugihara’s report raises another issue: the actual areas covered by the aerial drops. Did the total acreage come to 530, as Casey reported? Or was it 746, the number of acres in the plots that Sugihara monitored (and much closer to the 800 acres that Casey had told the EPA would be treated in her experiment)? Maps included with Sugihara’s report suggest that the pellets were distributed widely across all 746 acres in the four plots.
Excluding Plot 2 from the acreage covered leaves 529 acres in the remaining plots. If these formed the “530” acres that Casey reported treating, why would the transects in Plot 2 show such high densities of pellets – densities that are five times what would be expected if the rate of 17.8 pounds per acre had been applied evenly? Sugihara and his supervisor, Will Pitt, refused requests for an interview. A final answer to these questions awaits the release of additional information from investigating agencies.
Still, if the transects are to be credited with any degree of accuracy, it seems clear that enough bait could have been available to pigs to deliver a lethal dose. If Casey’s estimate of a pig needing to eat 441 pellets to become sick was in the ballpark, some 750 pigs could have been sickened by the 9,450 pounds of pellets dropped. No one suggests that that many pigs are in the area, which means that the pigs inhabiting the treated plots had access to far more than 441 pellets apiece. It is not a stretch to think that low pig densities, combined with a high rate of pellet distribution (possibly far higher than that reported), could have resulted in the pigs ingesting enough poison to cause the deaths that were observed.
A Pending Investigation
As Environment Hawai’i went to press, the state Department of Agriculture’s Pesticide Branch was continuing its investigation into the Keauhou experiment. Boesch, the branch chief, said it had not yet been determined whether his agency or the EPA would be issuing a notice of violation. Nor did he indicate whether the recipient would be Casey, her employer Kamehameha Schools, Eaton’s, or any of the other parties whose actions or inactions contributed to the calamitous experiment.
In the meantime, few materials relating to the investigation have been released. Necropsy reports on the pigs (both those found dead and those killed) were to have been done, but are not yet available for public review. The USDA Animal and Plant Health Inspection Service, which was so heavily involved in carrying out the experiment and monitoring its effects, has made it a national policy to refuse requests for information involving “private cooperators” – a decision based on an injunction issued by a court in Texas in a case in which an animal rights group had sought to learn which ranchers were using lethal collars to protect livestock from predators. (Calls to the APHIS public affairs office asking for further explanation of this policy were not returned by press time.)
Until the question of how the pigs at Keauhou died is resolved, no one in the community of researchers and land managers seeking desperately to control rats in the forest expects to be able to move forward with further plans to use aerial broadcasts of rodenticides in Hawai’i. “It saddens me that the pigs died,” said Peter Simmons of Kamehameha Schools. “But it also saddens me that it set our program back.”
– Patricia Tummons
1 LD50 refers to the dosage at which half the number of test animals die – i.e., receive a lethal dose.
2 Plot 2: 217 acres equals 878,199 square meters. With a mean density of .8 pellets per square meter, there would be 702,559 pellets in Plot 2, or 20,073 pounds of bait (a rate equivalent to 92.5 pounds per acre, or five times the reported distribution).
Plot 3: 140 acres equals 556,580 square meters. With a mean density of .45 pellets per square meter, there would be 250,461 pellets, or 7,156 pounds of bait (a rate equivalent to 51 pounds of bait per acre, or three times the reported distribution).
Plot 5: 176 acres equals 712,272 square meters. At a mean density of .7 pellets per square meter, there would be 498,590 pellets, or 14,245 pounds of bait (equivalent to 81 pounds per acre, or four and a half times the reported distribution).
Plot 6: 213 acres, or 862,011 square meters. At a mean distribution of .32 pellets per square meter, that comes to 275,843 pellets, or 7,881 pounds of bait (equivalent to 37 pounds per acre, more than twice the reported distribution). If the transects are representative of the actual bait in each plot, the total amount of bait that would have been present in the plots at the time of the transects comes to 49,355 pounds (25 tons).
— Patricia Tummons
Volume 14, Number 11 May 2004
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